2. Central Nervous System

Authors: Dahnert, Wolfgang

Title: Radiology Review Manual, 6th Edition

Copyright 2007 Lippincott Williams & Wilkins

> Table of Contents > Central Nervous System

Central Nervous System

Differential Diagnosis of Skull and Spine Disorders

Low back pain

Low Back Pain in Childhood

• Spondylosis, spondylolisthesis

• Osteomyelitis, diskitis

• Leukemia

• Histiocytosis X

• Osteoid osteoma

Lumbosacral Postsurgical Syndrome

• = Failed back surgery syndrome

• = signs of dysfunction and disability + pain and paresthesia following surgery

• Interpretation in immediate postoperative period difficult, stabilization of findings occurs in 2 6 months

Frequency: failure of improvement in 5 15%

• OSSEOUS CAUSES

  • Spondylolisthesis

  • Central stenosis

  • Foraminal stenosis

  • Pseudarthrosis

• SOFT-TISSUE CAUSES

  • Perioperative intraspinal hemorrhage

    (onset <1 week)

  • Residual disk herniation

    (onset <1 week)

  • Recurrent disk herniation

    (onset 1 week 1 month)

    no enhancement on early T1WI (appears enhanced 30 minutes post injection)

  • Spinal / meningeal / neural inflammation / infection

    (onset 1 week 1 month)

  • Intraspinal scar formation (onset >1 month)

    • Epidural fibrosis (scarring)

      • enhancing epidural plaque / mass

      • heterogeneous enhancement on early T1WI (maximum at about 5 minutes post injection)

    • Fibrosing arachnoiditis = adhesive arachnoiditis

      • thickened irregular clumped nerve roots

      • adhesion of roots to wall of thecal sac

      • abnormal enhancement of thickened meninges + matted nerve roots

• SURGICAL ERRORS

  • Wrong level / side of surgery

  • Direct nerve injury

• Remote phenomena unrelated to spine

  mnemonic: ABCDEF

  • Arachnoiditis

  • Bleeding

  • Contamination (infection)

  • Disk (residual / recurrent / new level)

  • Error (wrong disk excised)

  • Fibrosis (scar)

Cauda Equina Syndrome

• = constellation of signs + symptoms resulting from compressive lesion in lower lumbar spinal canal

Cause:

• displaced disk fragment

• intra- / extramedullary tumor

• osseous: Paget disease, osteomyelitis, osteoarthrosis of facet joints, complication of ankylosing spondylitis

• diminished sensation in lower lumbar + sacral

• dermatomes

• wasting + weakness of muscles

• decreased ankle reflexes

• impotence

• disturbed sphincter function + overflow incontinence

• decreased sphincter tone

Skull

Sutural Abnormalities

Wide Sutures

= >10 mm at birth, >3 mm at 2 years, >2 mm at 3 years of age; (sutures are splittable up to age 12 15; complete closure by age 30)

• NORMAL VARIANT

  in neonate + prematurity; growth spurt occurs at 2 3 years and 5 7 years

• Congenital underossification

  osteogenesis imperfecta, hypophosphatasia, rickets, hypothyroidism, pyknodysostosis, cleidocranial dysplasia

• METABOLIC DISEASE

  hypoparathyroidism; lead intoxication; hypo- / hypervitaminosis A

• RAISED INTRACRANIAL PRESSURE

  Cause:

  • intracerebral tumor

  • subdural hematoma

  • hydrocephalus

  Age: seen only if <10 years of age

  Location: coronal > sagittal > lambdoid > squamosal suture

• INFILTRATION OF SUTURES

  Cause: metastases to meninges from

  • neuroblastoma

  • leukemia

  • lymphoma

  poorly defined margins

• RECOVERY

  from

  • deprivational dwarfism

  • chronic illness

  • prematurity

  • hypothyroidism

P.178

Craniosynostosis

= CRANIOSTENOSIS = premature closure of sutures (normally at about 30 years of age)

Age: often present at birth; M:F = 4:1

Etiology:

• Primary craniosynostosis

• Secondary craniosynostosis

  • hematologic: sickle cell anemia, thalassemia

  • metabolic: rickets, hypercalcemia, hyperthyroidism, hypervitaminosis D

  • bone dysplasia: hypophosphatasia, achondroplasia, metaphyseal dysplasia, mongolism, Hurler disease, skull hyperostosis, Rubinstein-Taybi syndrome

  • syndromes: Crouzon, Apert, Carpenter, Treacher-Collins, cloverleaf skull, craniotelen-cephalic dysplasia, arrhinencephaly

  • microcephaly: brain atrophy / dysgenesis

  • after shunting procedures

Types:

Sagittal suture most commonly affected followed by coronal suture

• Scaphocephaly = Dolichocephaly (55%):

  premature closure of sagittal suture (long skull)

• Brachycephaly = Turricephaly (10%):

  premature closure of coronal / lambdoid sutures (short tall skull)

• Plagiocephaly (7%):

  unilateral early fusion of coronal + lambdoidal suture (lopsided skull)

• Trigonocephaly:

  premature closure of metopic suture (forward pointing skull)

• Oxycephaly:

  premature closure of coronal, sagittal, lambdoid sutures

• Cloverleaf skull = Kleeblattsch del:

  intrauterine premature closure of sagittal, coronal, lambdoid sutures;

  May be associated with: thanatophoric dysplasia

• sharply defined thickened sclerotic suture margins

• delayed growth of BPD in early pregnancy

Wormian Bones

• = intrasutural ossicles in lambdoid, posterior sagittal, temporosquamosal sutures; normal up to 6 months of age (most frequently)

• mnemonic: PORK CHOPS I

  • Pyknodysostosis

  • Osteogenesis imperfecta

  • Rickets in healing phase

  • Kinky hair syndrome

  • Cleidocranial dysostosis

  • Hypothyroidism / Hypophosphatasia

  • Oto-palato-digital syndrome

  • Primary acroosteolysis (Hajdu-Cheney) / Pachydermoperiostosis / Progeria

  • Syndrome of Down

  • Idiopathic

Increased Skull Thickness

• GENERALIZED

  • Chronic severe anemia (eg, thalassemia, sickle cell disease)

  • Cerebral atrophy following shunting of hydrocephalus

  • Engelmann disease: mainly skull base

  • Hyperparathyroidism

  • Acromegaly

  • Osteopetrosis

• FOCAL

  • Meningioma

  • Fibrous dysplasia

  • Paget disease

  • Dyke-Davidoff-Mason syndrome

  • Hyperostosis frontalis interna = dense hyperostosis of inner table of frontal bone; M < F

  mnemonic: HIPFAM

  • Hyperostosis frontalis interna

  • Idiopathic

  • Paget disease

  • Fibrous dysplasia

  • Anemia (sickle cell, iron deficiency, thalassemia, spherocytosis)

  • Metastases

Hair-on-end Skull

mnemonic: HI NEST

• Hereditary spherocytosis

• Iron deficiency anemia

• Neuroblastoma

• Enzyme deficiency (glucose-6-phosphate dehydrogenase deficiency causes hemolytic anemia)

• Sickle cell disease

• Thalassemia major

Leontiasis Ossea

= overgrowth of facial bones causing leonine (lionlike) facies

• Fibrous dysplasia

• Paget disease

• Craniometaphyseal dysplasia

• Hyperphosphatasia

Abnormally Thin Skull

• GENERALIZED

  • Obstructive hydrocephalus

  • Cleidocranial dysostosis

  • Progeria

  • Rickets

  • Osteogenesis imperfecta

  • Craniolacunia

• FOCAL

  • Neurofibromatosis

  • Chronic subdural hematoma

  • Arachnoid cyst

Inadequate Calvarial Calcification

• Achondroplasia

• Osteogenesis imperfecta

• Hypophosphatasia

P.179

Osteolytic Lesion of Skull

• NORMAL VARIANT

  • Emissary vein

    connecting venous systems inside + outside skull

    bony channel <2 mm in width

  • Venous lake

    • = outpouching of diploic vein

    • extremely variable in size, shape, and number

    • irregular well-demarcated contour

  • Fossae lacunae = pacchionian granulations

    • = agglomeration of hypertrophic arachnoid villi communicating with dural sinus

    • Age: >18 months; usually adulthood

    • usually multiple punched-out lesions with irregular contour in parasagittal location

    • Location: within 3 cm of superior sagittal sinus, anterior > posterior frontal bone

    • Site: inner table > diploe > outer table

  • Parietal foramina

    nonossification of embryonal rests in parietal fissure; bilateral at superior posterior angles of parietal bone; hereditary transmission

• TRAUMA

  • Surgical burr hole

  • Leptomeningeal cyst

• INFECTION

  • Osteomyelitis

  • Hydatid disease

  • Syphilis

  • Tuberculosis

• CONGENITAL

  • Epidermoid / dermoid

  • Neurofibromatosis (asterion defect)

  • Meningoencephalocele

  • Fibrous dysplasia

  • Osteoporosis circumscripta of Paget disease

• BENIGN TUMOR

  • Hemangioma

  • Enchondroma

  • Brown tumor

  • Eosinophilic granuloma

• MALIGNANT TUMOR

  • Solitary / multiple metastases

  • Multiple myeloma

  • Leukemia

  • Neuroblastoma

Solitary Lytic Lesion in Skull

mnemonic: HELP MFT HOLE

• Hemangioma

• Epidermoid / dermoid

• Leptomeningeal cyst

• Postop, Paget disease

• Metastasis, Myeloma

• Fibrous dysplasia

• Tuberculosis

• Hyperparathyroidism

• Osteomyelitis

• Lambdoid defect (neurofibromatosis)

• Eosinophilic granuloma

Multiple Lytic Lesions in Skull

mnemonic: BAMMAH

• Brown tumor

• AVM

• Myeloma

• Metastases

• Amyloidosis

• Histiocytosis

Lytic Area in Bone Flap

mnemonic: RATI

• Radiation necrosis

• Avascular necrosis

• Tumor

• Infection

Button Sequestrum

mnemonic: TORE ME

• Tuberculosis

• Osteomyelitis

• Radiation

• Eosinophilic granuloma

• Metastasis

• Epidermoid

Absent Greater Sphenoid Wing

mnemonic: M FOR MARINE

• Meningioma

• Fibrous dysplasia

• Optic glioma

• Relapsing hematoma

• Metastasis

• Aneurysm

• Retinoblastoma

• Idiopathic

• Neurofibromatosis

• Eosinophilic granuloma

Absence of Innominate Line

= Oblique carotid line

= vertical line projecting into orbit (on PA skull film) produced by orbital process of sphenoid

• CONGENITAL

  • Fibrous dysplasia

  • Neurofibromatosis

• INFECTION

• TUMOR

Widened Superior Orbital Fissure

mnemonic: A FAN

• Aneurysm (internal carotid artery)

• Fistula (cavernous sinus)

• Adenoma (pituitary)

• Neurofibroma

Tumors of Central Skull Base

• DEVELOPMENTAL

  • Encephalocele

• INFECTION / INFLAMMATION

  • Extension from paranasal sinus / mastoid infection

  • Complication of trauma

  P.180

  
  

  • Fungal disease: mucormycosis in diabetics, aspergillosis in immunosuppressed patients

  • Sinus + nasopharyngeal sarcoidosis

  • Radiation necrosis

• BENIGN

  • Juvenile angiofibroma

  • Meningioma

  • Chordoma

  • Pituitary tumor

  • Paget disease

  • Fibrous dysplasia

• MALIGNANT

  • Metastasis: prostate, lung, breast

  • Chondrosarcoma

  • Nasopharyngeal carcinoma

  • Rhabdomyosarcoma

  • Perineural tumor spread: head + neck neoplasm

Craniofacial Syndromes

= developmental malformations of the face + skull associated with CNS malformations

• Midfacial clefts

• Goldenhar syndrome

• Apert syndrome

• Crouzon syndrome

• Treacher-Collins syndrome

Maxilla and mandible

Maxillary Hypoplasia

• Down syndrome

• Drugs (alcohol, dilantin, valproate)

• Apert / Crouzon syndrome

• Achondroplasia

• Cleft lip / palate

Mandibular Hypoplasia = Micrognathia

• WITH ABNORMAL EARS

  • Treacher-Collins syndrome

  • Goldenhar syndrome (hemifacial microsomia) = facio-auriculo-vertebral spectrum (x-rays of vertebrae!)

  • Langer-Giedion syndrome (IUGR, protruding ears)

• ABNORMALITIES OF EARS + OTHER ORGANS

  • Miller syndrome (severe postaxial hand anomalies)

  • Velo-cardio-facial syndrome (hand + cardiac lesions)

  • Oto-palato-digital syndrome - type II (hand abnormalities)

  • Stickler syndrome (ear anomalies not severe)

  • Pierre-Robin syndrome (large fleshy ears)

• NO EAR ANOMALIES

  • Pyknodysostosis

• OTHERS

  • Seckel syndrome (bird-headed dwarfism)

  • Multiple pterygium syndrome

  • Pena-Shokeir syndrome

  • Beckwith-Wiedemann syndrome

  • Arthrogryposis

  • Skeletal dysplasias

  • Trisomy 13, 18, 9 (abnormal karyotype in 25%)

Destruction of Temporomandibular Joint

mnemonic: HIRT

• Hyperparathyroidism

• Infection

• Rheumatoid arthritis

• Trauma

Radiolucent Lesion of Mandible

• SHARPLY MARGINATED LESION

  • around apex of tooth

    • Radicular cyst

    • Cementoma

  • around unerupted tooth

    • Dentigerous cyst

    • Ameloblastoma

  • unrelated to tooth

    • Simple bone cyst

    • Fong disease

    • Basal cell nevus syndrome

• POORLY MARGINATED LESIONS

  floating teeth : suggestive of primary / secondary malignancy

  resorption of tooth root: hallmark of benign process

  • infection

    • Osteomyelitis: actinomycosis

  • radiotherapy

    • Osteoradionecrosis

  • malignant neoplasm

    • Osteosarcoma (1/3 lytic, 1/3 sclerotic, 1/3 mixed)

    • Local invasion from gingival / buccal neoplasms (more common)

    • Metastasis from breast, lung, kidney in 1% (in 70% adenocarcinoma)

  • other

    • Eosinophilic granuloma: floating tooth

    • Fibrous dysplasia

    • Osteocementoma

    • Ossifying fibroma (very common)

Cystic Lesion of Jaw

• ODONTOGENIC WITHOUT MINERALIZATION

  • = mostly benign lesion developing during / after formation of teeth

  • asymptomatic / pain swelling

  • paresthesia, tooth displacement / mobility

  • radiolucent

    • Ameloblastoma = adamantinoma of jaw

      • = benign locally aggressive epithelial neoplasm

      • Prevalence: 10% of odontogenic tumors

      • Origin: enamel-type epithelial tissue elements around tooth; 30 50% arise from epithelium of dentigerous cyst (= mural ameloblastoma)

      • Age: 3rd 5th decade; M:F = 1:1

      • slow-growing painless mass

      • Location: ramus + posterior body of mandible (75%), maxilla (25%)

      • Site: in region of bicuspids + molars (angle of mandible commonly affected)

      • well-defined well-corticated unilocular lucent lesion (DDx: odontogenic keratocyst, dentigerous cyst)

      P.181

      
      

      • multilocular lesion with internal septations (honeycomb / soap bubble appearance)

      • typically expansile with scalloped margin

      • may perforate the lingual cortex + infiltrate adjacent soft tissues

      • often associated with the crown of an impacted / unerupted tooth

      • resorption of the root of a tooth

      • Prognosis: frequently local recurrence even more aggressive after excision

    • Odontogenic keratocyst

      • Origin: dental lamina + other sources of odontogenic epithelium

      • Prevalence: 5 15% of all jaw cysts

      • Age: 2nd 4th decade

      • Path: daughter cysts + nests of cystic epithelia in vicinity (high rate of recurrence)

      • Histo: parakeratinized lining epithelium + cheesy material in lumen of lesion

      • Location: body + ramus of mandible (most often); may be anywhere in mandible / maxilla

      • unilocular lucent lesion with smooth corticated border

      • often associated with impacted tooth

      • undulating borders / multilocular appearance

      • cortical thinning, tooth displacement, root resorption

      • DDx: indistinguishable from dentigerous cyst / ameloblastoma

    • Dentigerous cyst = follicular cyst

    • Prevalence: most common type of noninflammatory odontogenic cyst

    • Path: epithelial-lined cyst from odontogenic epithelium developing around unerupted tooth

    • Histo: forms within lining of dental follicle

    • Age: adolescent / young adult

    • typically painfree

    • Location: mandible, maxilla (may expand into maxillary sinus)

    • Site: around the crown of an unerupted tooth (usually 3rd molar)

    • cystic expansile pericoronal lesion containing impacted tooth

    • root of tooth often outside lesion

    • well-defined round / ovoid corticated lucent lesion mandibular expansion

    • Cx: may degenerate into mural ameloblastoma (rare)

    • DDx: unilocular odontogenic keratocyst

  • Radicular cyst = periapical cyst

    • Prevalence: most common cyst of the jaw

    • Cause: periapical inflammatory lesion secondary to pulpal necrosis in deep carious lesion / deep filling / trauma

    • Age: 30 50 years

    • Site: intimately associated with apex of nonvital tooth

    • round / pear-shaped unilocular periapical lucent lesion, usually <1 cm in diameter

    • bordered by thin rim of cortical bone

    • displacement of adjacent teeth

    • mild root resorption

    • DDx: periapical granuloma

• ODONTOGENIC WITH MINERALIZATION

  = elaborate enamel, dentin, cementum

  varying degrees of opacity

  • Odontoma

    • = odontogenic hamartomatous malformation

    • Prevalence: most common odontogenic mass (67%)

    • Age: 2nd decade

    • 1 3 cm in diameter

    • may be surrounded by lucent follicle

    • Types:

      • compound odontoma (more common)

        multiple teeth / tooth-like structures

    • complex odontoma

      = multiple masses of dental tissue

      well-defined lesion with amorphous calcifications

  • Cx: impaction, malpositioning, resorption of adjacent teeth

  • DDx: focal cemento-osseous dysplasia, ameloblastic fibro-odontoma, adenomatoid odontogenic tumor

• Odontogenic myxoma

• Prevalence: 3 6% of odontogenic tumors

• Origin: mesenchymal odontogenic tissue

• Age: 10 30 years; M < F

• usually painless

• Location: maxilla > mandible

• well-demarcated / ill-defined lytic lesion of varying size

• often multilocular with honeycomb-like internal structure

• foci of irregular calcifications (frequent)

• Cx: can be locally aggressive causing considerable destruction of adjacent bone + soft-tissue infiltration

• DDx: malignancy, traumatic bone cyst, central giant cell granuloma, calcifying epithelial odontogenic tumor

• Nonodontogenic

  • Ossifying fibroma (conventional slow-growing ossifying fibroma, juvenile active aggressive ossifying fibroma)

    • = encapsulated circumscribed benign neoplasm

      Histo: highly cellular fibrous connective tissue containing varying amounts of osteoid, bone, cementum, cementum-like calcified tissue

    • asymptomatic

    • facial asymmetry due to bone expansion

    • tooth displacement

    • initially lucent + later often opaque lesion (depending on degree of calcification)

    • surrounded by thin line of lucency (= fibrous capsule) + in turn surrounded by thin sclerotic rim of reactive bone

    • intense focal uptake on bone scan

    P.182

    
    

    • DDx: odontoma, sequestrum, fibrous dysplasia, vascular lesion

  • Focal cemento-osseous dysplasia

    • = nonneoplastic benign fibro-osseous lesion

    • Age: adult life

    • asymptomatic

    • Location: mandible >> maxilla

    • one / more, closely apposed / confluent, round / ovoid lucent lesion with varying amounts of opacity

    • initially cystic lucency + later progressively more opaque internally

    • no extension into adjacent bone

    • no cortical expansion

    • DDx: periapical periodontitis, ossifying fibroma

  • Periapical cemento-osseous dysplasia

    • (= cementoma) = fibro-osteoma

    • Age: 30 40 years of age; most common in women

    • asymptomatic

    • Location: in anterior portion of mandible

    • Site: at apex of vital tooth

    • often multicentric

    • mixed lucent + sclerotic lesion with little expansion, calcifies with time

    • DDx: ossifying fibroma, fibrous dysplasia, Paget disease

  • Florid osseous dysplasia

    • Age: adult life

    • asymptomatic

    • diffuse multiquadrant distribution of mixed lucent-opaque osseous changes

  • Traumatic bone cyst

    • = not a true cyst for lack of epithelial lining

    • Cause: ? response to trauma

    • Age: 2nd decade

    • asymptomatic

    • Location: mandible

    • unilocular sharply marginated lucent defect

    • scalloped superior margin with fingerlike projections extending between roots of teeth

    • thinning of mandibular cortex osseous expansion

    • DDx: vascular lesion, central giant cell granuloma, ossifying fibroma

  • Lingual salivary gland inclusion defect

    • = well-defined depression in lingual surface of mandible (= Stafne cyst)

    • Path: aberrant lobe of submandibular gland / fat

    • asymptomatic

    • Location: usually near mandibular angle

    • Site: just above inferior border of mandible, anterior to angle of jaw, inferior to mandibular canal, posterior to 3rd molar

    • oval / rectangular well-defined area of lucency

    • border surrounded by an opaque line

    • may extend to buccal cortex

    • DDx: arteriovenous malformation

  • Central giant cell granuloma (common)

    • Age: <30 years (75%)

    • painless swelling, tenderness on palpation

    • Location: mandible:maxilla = 2:1

    • Site: anterior to 1st molar (= deciduous teeth); propensity for crossing midline (especially in maxilla)

    • unilocular area of lucency (early)

    • multilocular with wispy internal septa (later)

    • expansion of bone + displacement of teeth

    • usually well-defined border

    • DDx: brown tumor of HPT (histologically similar)

  • Brown tumor of hyperparathyroidism

    • = osteoclastoma = central giant cell lesion in patients with long-standing HPT

    • hypercalcemia, hypophosphatemia

    • elevated levels of parathyroid hormone

    • variably defined margin cortical expansion

    • generalized demineralization of medullary bones of jaw

    • loss of lamina dura around roots of teeth

  • Arteriovenous malformation

    • Tooth extraction can result in lethal exsanguination!

    • occasionally pulsatile soft-tissue swelling

    • Location: ramus + posterior body of mandible

    • cystlike due to bone resorption calcifications

    • multilocular bone expansion

    • erosive margins

    • angiogram confirms diagnosis

    • DDx: traumatic bone cyst, central giant cell granuloma, ossifying fibroma

  • Mucoepidermoid carcinoma

Tooth Mass

• CYSTIC LESION

  • Radicular cyst = periapical cyst

  • Ameloblastoma = adamantinoma of jaw

  • Giant cell reparative granuloma

  • Primordial cyst

    arising from follicle of tooth that never developed

  • Traumatic bone cyst

  • Dentigerous cyst = follicular cyst

  • Odontogenic keratocyst

• SCLEROTIC LESION

  • Cementoma

  • True cementoma = benign cementoblastoma

  • Gigantiform cementoma

  • Hypercementosis

    = bulbous enlargement of a root

    • idiopathic

    • associated with Paget disease

  • Benign fibro-osseous lesions

    • ossifying fibroma: young adults; mandible > maxilla

    • monostotic fibrous dysplasia: M < F, younger patients

    • condensing osteitis = focal chronic sclerosing osteitis

    near apex of nonvital tooth

  • Paget disease

    • involvement of jaw in 20%; maxilla > mandible

    • Location: bilateral, symmetric involvement

    • widened alveolar ridges

    • flat palate

    P.183

    
    

    • loosening of teeth

    • hypercementosis

    • may cause destruction of lamina dura

  • Torus mandibularis = exostosis

    Site: midline of hard palate; lingual surface of mandible in region of bicuspids

Craniovertebral junction

Craniovertebral Junction Anomaly

Basilar Invagination

= primary developmental anomaly with abnormally high position of vertebral column prolapsing into skull base

Associated with: Chiari malformation, syringohydromyelia in 25 35%

Cause:

• Condylus tertius = ossicle at distal end of clivus

  pseudojoint with odontoid process / anterior arch of C1

• Condylar hypoplasia

  • lateral masses of atlas may be fused to condyles

  • violation of Chamberlain line

  • widening of atlanto-occipital joint axis angle

  • tip of odontoid >10 mm above bimastoid line

• Basiocciput hypoplasia

  • shortening of clivus

  • violation of Chamberlain line

  • clivus-canal angle typically decreased

• Atlanto-occipital assimilation

  • = complete / partial failure of segmentation between skull + 1st cervical vertebra

  • violation of Chamberlain line

  • clivus-canal angle decreased

  • May be associated with: fusion of C2 + C3

  • Cx: atlantoaxial subluxation (50%); sudden death

limitation in range of motion of CVJ

abnormal craniometry

C-spine + foramen magnum bulge into cranial cavity

elevation of posterior arch of C1

Basilar Impression

= acquired form of basilar invagination with bulging of C-spine and foramen magnum into cranial cavity

tip of odontoid process projects >5 mm above Chamberlain line (= line between hard palate + opisthion)

Cause: Paget disease, osteomalacia, rickets, fibrous dysplasia, hyperparathyroidism, Hurler syndrome, osteogenesis imperfecta, skull base infection

mnemonic: PF ROACH

• Paget disease

• Fibrous dysplasia

• Rickets

• Osteogenesis imperfecta, Osteomalacia

• Achondroplasia

• Cleidocranial dysplasia

• Hyperparathyroidism, Hurler syndrome

Platybasia

• = anthropometric term referring to flattening of skull base

• May be associated with: basilar invagination

• cord symptoms

• craniovertebral = clivus-canal angle becomes acute (<150 )

• Welcher basal angle = sphenoid angle >140

• bowstring deformity of cervicomedullary junction

Atlas and axis

Atlas Anomalies

• POSTERIOR ARCH ANOMALIES

  • Posterior atlas arch rachischisis (4%)

    • Location: midline (97%), lateral through sulcus of vertebral artery (3%)

    • absence of arch-canal line (LAT view)

    • superimposed on odontoid process / axis body simulating a fracture (open-mouth odontoid view)

  • Total aplasia of posterior atlas arch

  • Keller-type aplasia with persistence of posterior tubercle

  • Aplasia with uni- / bilateral remnant + midline rachischisis

  • Partial / total hemiaplasia of posterior arch

• ANTERIOR ARCH ANOMALIES

  • Isolated anterior arch rachischisis (0.1%)

  • Split atlas = anterior + posterior arch rachischisis

    • plump rounded anterior arch overlapping the odontoid process making identification of predental space impossible (LAT view)

    • duplicated anterior margins (LAT view)

Axis Anomalies

• Persistent ossiculum terminale = Bergman ossicle

  unfused odontoid process >12 years of age

  DDx: type 1 odontoid fracture

• Odontoid aplasia (extremely rare)

• Os odontoideum

  • = independent os cephalad to axis body in location of odontoid process

  • absence of odontoid process

  • anterior arch of atlas hypertrophic + situated too far posterior in relation to axis body

  • Cx: atlantoaxial instability

  • DDx: type 2 odontoid fracture (uncorticated margin)

    

    Primary and Secondary Ossification Centers

P.184

Odontoid Erosion

mnemonic: P LARD

• Psoriasis

• Lupus erythematosus

• Ankylosing spondylitis

• Rheumatoid arthritis

• Down syndrome

Atlantoaxial Subluxation

= displacement of atlas with respect to axis

• Posterior atlantoaxial subluxation (rare)

• Anterior atlantoaxial subluxation (common)

  • = distance between dens + anterior arch of C1 (measurement along midplane of atlas on lateral view):

    • predental space: >2.5 mm; >4.5 mm (in children)

    • retrodental space: <18 mm

Causes of subluxation:

• Congenital

  • Occipitalization of atlas

    0.75% of population; fusion of basion + anterior arch of atlas

  • Congenital insufficiency of transverse ligament

  • Os odontoideum / aplasia of dens

  • Down syndrome (20%)

  • Morquio syndrome

  • Bone dysplasia

• Arthritis

  due to laxity of transverse ligament or erosion of dens

  • Rheumatoid arthritis

  • Psoriatic arthritis

  • Reiter syndrome

  • Ankylosing spondylitis

  • SLE

  rare: in gout + CPPD

• Inflammatory process

  pharyngeal infection in childhood, retropharyngeal abscess, coryza, otitis media, mastoiditis, cervical adenitis, parotitis, alveolar abscess

  dislocation 8 10 days after onset of symptoms

• Trauma (very rare without odontoid fracture)

• Marfan disease

mnemonic: JAP LARD

• Juvenile rheumatoid arthritis

• Ankylosing spondylitis

• Psoriatic arthritis

• Lupus erythematosus

• Accident (trauma)

• Retropharyngeal abscess, Rheumatoid arthritis

• Down syndrome

Pseudosubluxation of Cervical Spine

= ligamentous laxity in infants allows for movement of the vertebral bodies on each other, esp. C2 on C3

Spinal dysraphism

= abnormal / incomplete fusion of midline embryologic mesenchymal, neurologic, bony structures

External signs (in 50%):

subcutaneous lipoma	spastic gait disturbance
hypertrichosis	foot deformities
pigmented nevi	absent tendon reflexes
skin dimple	sinus tract
bladder + bowel dysfunction
pathologic plantar response

Spina Bifida

= incomplete closure of bony elements of the spine (lamina + spinous processes) posteriorly

Spina Bifida Occulta

= OCCULT SPINAL DYSRAPHISM

= cleft / tethered cord WITH skin cover

Frequency: 15% of spinal dysraphism

rarely leads to neurologic deficit in itself

Associated with:

• vertebral defect (85 90%)

• lumbosacral dermal lesion (80%): hairy tuft (= hypertrichosis), dimple, sinus tract, nevus, hyperpigmentation, hemangioma, subcutaneous mass

  • Diastematomyelia

  • Lipomeningocele

  • Tethered cord syndrome

  • Filum terminale lipoma

  • Intraspinal dermoid

  • Epidermoid cyst

  • Myelocystocele

  • Split notochord syndrome

  • Meningocele

  • Dorsal dermal sinus

  • Tight filum terminale syndrome

Spina Bifida Aperta

= SPINA BIFIDA CYSTICA

= posterior protrusion of all / parts of the contents of the spinal canal through a bony spinal defect

Frequency: 85% of spinal dysraphism

Associated with: hydrocephalus, Arnold-Chiari II malformation

• Most severe form of midline fusion defect

• neural placode WITHOUT skin cover

• associated with neurologic deficit in >90%

• Simple meningocele

  = herniation of CSF-filled sac without neural elements

• Myelocele

  = midline plaque of neural tissue lying exposed at the skin surface

• Myelomeningocele

  = a myelocele elevated above skin surface by expansion of subarachnoid space ventral to neural plaque

• Myeloschisis

  = surface presentation of neural elements completely uncovered by meninges

Caudal Spinal Anomalies

= malformation of distal spine and cord in association with hindgut, renal, and genitourinary anomalies

• Terminal myelocystocele

• Lateral meningocele

• Caudal regression

P.185

Segmentation Anomalies of Vertebral Bodies

Clefts in Neural Arch

during 9 12th week of gestation two ossification centers form for the ventral + dorsal half of vertebral body

• Asomia = agenesis of vertebral body

  • complete absence of vertebral body

  • hypoplastic posterior elements may be present

• Hemivertebra

  • Unilateral wedge vertebra

    • right / left hemivertebra

    • scoliosis at birth

  • Dorsal hemivertebra

    • rapidly progressive kyphoscoliosis

  • Ventral hemivertebra (extremely rare)

• Coronal cleft

  • = failure of fusion of anterior + posterior ossification centers

  • May be associated with: premature male infant, Chondrodystrophia calcificans congenita

  • Location: usually in lower thoracic + lumbar spine

  • vertical radiolucent band just behind midportion of vertebral body; disappears mostly by 6 months of life

• Butterfly vertebra

  • = failure of fusion of lateral halves secondary to persistence of notochordal tissue

  • May be associated with: anterior spina bifida anterior meningocele

  • widened vertebral body with butterfly configuration (AP view)

  • adaptation of vertebral endplates of adjacent vertebral bodies

• Block vertebra

  • = congenital vertebral fusion

    Location: lumbar / cervical

  • height of fused vertebral bodies equals the sum of heights of involved bodies + intervertebral disk

  • waist at level of intervertebral disk space

• Hypoplastic vertebra

• Klippel-Feil syndrome

Vertebral body

Destruction of Vertebral Body

• NEOPLASM

  • Metastasis

  • Primary neoplasm: lymphoma, multiple myeloma, chordoma

• INFECTION

  • Pyogenic vertebral osteomyelitis

  • Tuberculous spondylitis

  • Brucellosis

  • Fungal disease

  • Echinococcosis

  • Sarcoidosis

Gas in Vertebral Body

• Osteonecrosis = K mmell disease: linear collection

• Osteomyelitis: small gas bubbles extension into adjacent soft-tissues

• Intraosseous displacement of cartilaginous / Schmorl node: branching gas pattern

• Malignancy

Small Vertebral Body

• Radiation therapy

  during early childhood in excess of 1,000 rads

• Juvenile rheumatoid arthritis

  • Location: cervical spine

  • atlantoaxial subluxation may be present

  • vertebral fusion may occur

• Eosinophilic granuloma

  • Location: lumbar / lower thoracic spine

  • compression deformity / vertebra plana

• Gaucher disease

  • = deposits of glucocerebrosides within RES

  • compression deformity

• Platyspondyly generalisata

  • = flattened vertebral bodies associated with many hereditary systemic disorders (achondroplasia, spondyloepiphyseal dysplasia tarda, mucopolysaccharidosis, osteopetrosis, neurofibromatosis, osteogenesis imperfecta, thanatophoric dwarfism)

  • disk spaces of normal height

Vertebra Plana

mnemonic: FETISH

• Fracture (trauma, osteogenesis imperfecta)

• Eosinophilic granuloma

• Tumor (metastasis, myeloma, leukemia)

• Infection

• Steroids (avascular necrosis)

• Hemangioma

Signs of Acute Vertebral Collapse on MRI

• OSTEOPOROSIS

  • retropulsion of posterior bone fragment

• MALIGNANCY

  • epidural soft-tissue mass

  • no residual normal marrow signal intensity

  • abnormal enhancement

P.186

Enlarged Vertebral Body

• Paget disease

  • picture framing ; bone sclerosis

• Gigantism

  • increase in height of body + disk

• Myositis ossificans progressiva

  • bodies greater in height than width

  • osteoporosis

  • ossification of ligamentum nuchae

Enlarged Vertebral Foramen

• Neurofibroma

• Congenital absence / hypoplasia of pedicle

• Dural ectasia (Marfan syndrome, Ehlers-Danlos syndrome)

• Intraspinal neoplasm

• Metastatic destruction of pedicle

Cervical Spine Fusion

mnemonic: SPAR BIT

• Senile hypertrophic ankylosis (DISH)

• Psoriasis, Progressive myositis ossificans

• Ankylosing spondylitis

• Reiter disease, Rheumatoid arthritis (juvenile)

• Block vertebra (Klippel-Feil)

• Infection (TB)

• Trauma

Vertebral Border Abnormality

Straightening of Anterior Border

• Ankylosing spondylitis

• Paget disease

• Psoriatic arthritis

• Reiter disease

• Rheumatoid arthritis

• Normal variant

Anterior Scalloping of Vertebrae

• Aortic aneurysm

• Lymphadenopathy

• Tuberculosis

• Multiple myeloma (paravertebral soft-tissue mass)

Posterior Scalloping of Vertebrae

in conditions associated with dural ectasia

• INCREASED INTRASPINAL PRESSURE

  • Communicating hydrocephalus

  • Ependymoma

• MESENCHYMAL TISSUE LAXITY (dural ectasia)

  • Neurofibromatosis

  • Marfan syndrome

  • Ehlers-Danlos syndrome

  • Posterior meningocele

• BONE SOFTENING

  • Mucopolysaccharidoses: Hurler, Morquio, Sanfilippo

  • Achondroplasia

  • Acromegaly (lumbar vertebrae)

  • Ankylosing spondylitis (lax dura acting on osteoporotic vertebrae)

mnemonic: DAMN MALE SHAME

• Dermoid

• Ankylosing spondylitis

• Meningioma

• Neurofibromatosis

• Marfan syndrome

• Acromegaly

• Lipoma

• Ependymoma

• Syringohydromyelia

• Hydrocephalus

• Achondroplasia

• Mucopolysaccharidoses

• Ehlers-Danlos syndrome

Bony Outgrowths from Vertebra

• CHILDHOOD

  • Hurler syndrome = gargoylism

    • rounded appearance of vertebral bodies

    • mild kyphotic curve with smaller vertebral body at apex of kyphosis displaying tonguelike beak at anterior half (usually at T12 / L1)

    • step-off deformities along anterior margins

  • Hunter syndrome

    less severe changes than in Hurler syndrome

  • Morquio disease

    • flattened + widened vertebral bodies

    • anterior tonguelike elongation of central portion of vertebral bodies

  • Hypothyroidism = cretinism

    • small flat vertebral bodies

    • anterior tonguelike deformity (in children only)

    • widened disk spaces + irregular endplates

• ADULTS

  • Spondylosis deformans

    • osteophytosis along anterior + lateral aspects of endplates with horizontal + vertical course as a result of shearing of the outer annular fibers (Sharpey fibers connecting the annulus fibrosus to adjacent vertebral body)

  • Diffuse idiopathic skeletal hyperostosis (DISH)

    • flowing calcifications + ossifications along anterolateral aspect of >4 contiguous thoracic vertebral bodies osteophytosis

  • Ankylosing spondylitis

    • bilateral symmetric syndesmophytes (ossification of annulus fibrosus)

    • bamboo spine

      

      Syndesmophytes

    P.187

    
    

    • diskal ballooning = biconvex intervertebral disks secondary to osteoporotic deformity of endplates

    • straightening of anterior margins of vertebral bodies (erosion)

    • ossification of paraspinal ligaments

  • Fluorosis

    • vertebral osteophytosis + hyperostosis

    • sclerotic vertebral bodies + kyphoscoliosis

    • calcification of paraspinal ligaments

  • Acromegaly

    • increase in anteroposterior diameter of vertebrae + concavity on posterior portion

    • enlargement of intervertebral disk

  • Hypoparathyroidism

  • Neuropathic arthropathy

  • Sternoclavicular hyperostosis

Spine Ossification

• Syndesmophyte = ossification of annulus fibrosus

  • thin slender vertical outgrowth extending from margin of one vertebral body to next

  • Associated with: ankylosing spondylitis, ochronosis

• Osteophyte

  • = ossification of anterior longitudinal ligament

  • initially triangular outgrowth several millimeters from edge of vertebral body

  • Associated with: osteoarthritis

• Flowing anterior ossification

  • = ossification of disk, anterior longitudinal ligament, paravertebral soft tissues

  • Associated with: DISH

• Paravertebral ossification

  • initially irregular / poorly defined paravertebral ossification eventually merging with vertebral body

  • Associated with: psoriatic arthritis, Reiter syndrome

Vertebral Endplate Abnormality

• Cupid's bow vertebra

  • Cause: ? (normal variant)

  • Location: 3 5th lumbar vertebra

  • two parasagittal posterior concavities on inferior aspect of vertebral body (viewed on AP)

• Osteoporosis (senile / steroid-induced)

  • fish / fish-mouth vertebrae

    Cause: osteomalacia, Paget disease, hyperparathyroidism, Gaucher disease

    biconcave vertebrae

    bone sclerosis along endplates

  • wedge-shaped vertebrae

    • anterior border height reduced by >4 mm compared to posterior border height

  • pancake vertebrae

    • overall flattening of vertebra

  • H-vertebrae

    • = compression of central portions from subchondral infarcts

    • Cause: sickle cell + other anemias, Gaucher disease

  • Schmorl / cartilaginous node

    • = intraosseous herniation of nucleus pulposus at center of weakened endplate

      

      Vertebral Endplate Abnormalities

    • Cause: Scheuermann disease, trauma, hyperparathyroidism, osteochondrosis

  • Butterfly vertebra

    Cause: congenital defect

  • Ring epiphysis

  • Limbus vertebrae

    • = intraosseous herniation of disk material at junction of vertebral bony rim of centra + endplate (anterosuperior corner)

  • Rugger-jersey spine

    • Cause: hyperparathyroidism, myelofibrosis

    • horizontal sclerosis subjacent to vertebral endplates with intervening normal osseous density (resembling the stripes on rugby jerseys)

  • Sandwich / hamburger vertebrae

    • Cause: osteopetrosis, myelofibrosis

    • sclerotic endplates alternate with radiolucent midportions of vertebral bodies

Ring Epiphysis

= normal aspect of developing vertebra (between 6 and 12 years of age)

small steplike recess at corner of anterior edge of vertebral body

• Severe osteoporosis

• Healing rickets

• Scurvy

Bullet-shaped Vertebral Body

mnemonic: HAM

• Hypothyroidism

• Achondroplasia

• Morquio syndrome

Bone-within-bone Vertebra

= ghost vertebra following stressful event during vertebral growth phase in childhood

• Stress line of unknown cause

• Leukemia

• Heavy metal poisoning

• Thorotrast injection, TB

• Rickets

• Scurvy

• Hypothyroidism

• Hypoparathyroidism

P.188

Ivory Vertebra

mnemonic: LOST FROM CHOMP

• Lymphoma

• Osteopetrosis

• Sickle cell disease

• Trauma, Tuberculous spondylitis

• Fluorosis

• Renal osteodystrophy

• Osteoblastic metastasis

• Myelosclerosis

• Chronic sclerosing osteomyelitis, Chordoma

• Hemangioma

• Osteosarcoma

• Myeloma

• Paget disease

Sclerotic Pedicle

• Osteoid osteoma

• Unilateral spondylolysis

• Contralateral congenitally absent pedicle

Tumor of vertebra

Expansile Lesion of Vertebrae

• INVOLVEMENT OF MULTIPLE VERTEBRAE

  • Metastases, multiple myeloma / plasmacytoma, lymphoma, hemangioma, Paget disease, angiosarcoma, eosinophilic granuloma

• INVOLVEMENT OF TWO / MORE CONTIGUOUS VERTEBRAE

  • Osteochondroma, chordoma, aneurysmal bone cyst, myeloma

• BENIGN LESION

  • Osteochondroma (1 5% with solitary osteochondromas, 7 9% with hereditary multiple exostoses) commonly cervical, esp. C2; commonly rising from posterior elements

  • Osteoblastoma (30 40% in spine)

    • M:F = 2:1; equal distribution in spine; posterior elements (lamina, pedicle), may involve body if large; expansile lesion with sclerotic / shell-like rim, foci of calcified tumor matrix in 50%

  • Giant cell tumor (5 7% in spine)

    • commonly sacrum, expansile lytic lesion of vertebral body with well-defined borders; secondary invasion of posterior elements; malignant degeneration in 5 20% after radiation therapy

  • Osteoid osteoma (10 25% in spine)

    • commonly lower thoracic / upper lumbar spine, posterior elements (pedicle, lamina, spinous process), painful scoliosis with concavity toward lesion

  • Aneurysmal bone cyst (12 30% in spine)

    • thoracic > lumbar > cervical spine, posterior elements with frequent extension into vertebral bodies, well-defined margins, may arise from primary bone lesion (giant cell tumor, fibrous dysplasia) in 50%, may involve two contiguous vertebrae

  • Hemangioma (30% in spine)

    • 10% incidence in general population; commonly lower thoracic / upper lumbar spine, vertebral body, accordion / corduroy appearance

  • Hydatid cyst (1% in spine)

    • slow-growing destructive lesion, well-defined sclerotic borders, endemic areas

  • Paget disease

    • vertebral body posterior elements, enlargement of bone, picture framing ; bone sclerosis

  • Eosinophilic granuloma (6% in spine)

    • most often cervical / lumbar spine, vertebral body, vertebra plana ; multiple involvement common

  • Fibrous dysplasia (1% in spine)

    • vertebral body, nonhomogeneous trabecular ground-glass appearance

  • Enostosis (1 14% in spine)

    • Location: T1 T7 > L2 L3

• MALIGNANT

  • Chordoma (15% in spine)

    • most common nonlymphoproliferative primary malignant tumor of the spine in adults; particularly C2, within vertebral body; violates disk space

  • Metastasis (especially from lung, breast)

    Age: >50 years of age;

    Clue: pedicles often destroyed

  • Multiple myeloma / plasmacytoma

    Clue: vertebral pedicles usually spared

  • Angiosarcoma

    10% involve spine, most commonly lumbar

  • Chondrosarcoma (3 12% in spine)

    2nd most common nonlymphoproliferative primary malignant tumor of the spine in adults

    Site: vertebral body (15%), posterior elements (40%), both (45%)

    involvement of adjacent vertebra by extension through disk (35%)

  • Ewing sarcoma and PNET

    most common nonlymphoproliferative primary malignant tumor of the spine in children; metastases more common than primary

    Site: vertebral body with extension to posterior elements

    diffuse sclerosis + osteonecrosis (69%)

  • Osteosarcoma (0.6 3.2% in spine)

    Average age: 4th decade

    Location: lumbosacral segments

    Site: vertebral body, posterior elements (10 17%)

    may present as ivory vertebra

  • Lymphoma

Blowout Lesion of Posterior Elements

mnemonic: GO APE

• Giant cell tumor

• Osteoblastoma

• Aneurysmal bone cyst

• Plasmacytoma

• Eosinophilic granuloma

Bone Tumors Favoring Vertebral Bodies

mnemonic: CALL HOME

• Chordoma

• Aneurysmal bone cyst

P.189




• Leukemia

• Lymphoma

• Hemangioma

• Osteoid osteoma, Osteoblastoma

• Myeloma, Metastasis

• Eosinophilic granuloma

Primary Vertebral Tumors in Children

[in order of frequency:]

• Osteoid osteoma

• Benign osteoblastoma

• Aneurysmal bone cyst

• Ewing sarcoma

Primary Tumor of Posterior Elements

mnemonic: A HOG

• Aneurysmal bone cyst

• Hydatid cyst, Hemangioma

• Osteoblastoma, Osteoid osteoma

• Giant cell tumor

Sacrum

Destructive Sacral Lesion

mnemonic: SPACEMON

• Sarcoma

• Plasmacytoma

• Aneurysmal bone cyst

• Chordoma

• Ependymoma

• Metastasis

• Osteomyelitis

• Neuroblastoma

Sacral Tumor

Sacral Bone Tumor

• BENIGN

  • Giant cell tumor (2nd most common primary)

  • Aneurysmal bone cyst (rare)

  • Cavernous hemangioma (very rare)

  • Osteoid osteoma / osteoblastoma (very rare)

• MALIGNANT

  • Metastases (most common sacral neoplasm):

    • hematogenous: lung, breast, kidney, prostate

    • contiguous: rectum, uterus, bladder

  • Plasmacytoma, multiple myeloma

  • Lymphoma, leukemia

  • Chordoma (most common primary)

    • 2 4% of malignant osseous neoplasms!

  • Sacrococcygeal teratoma

  • Ewing sarcoma (rare)

Sacral Canal Tumor (less common)

• BENIGN

  • Neurofibroma: multiple suggestive of NF

  • Schwannoma (rare)

  • Meningioma (very rare)

• MALIGNANT

  • Ependymoma

  • Drop metastases

  • Carcinoid tumor

Intervertebral disk

Loss of Disk Space

• Degenerative disk disease

• Neuropathic osteoarthropathy

• Dialysis spondyloarthropathy with amyloidosis

• Ochronosis

• Ankylosing spondylitis with pseudarthrosis

• Sarcoidosis

Spinal Vacuum Phenomena

nucleus pulposus	Osteochondrosis
annulus fibrosus	Spondylosis deformans
disk within vertebral body	Cartilaginous node
disk within spinal canal	Intraspinal disk herniation
apophyseal joint	Osteoarthritis
vertebral body	Ischemic necrosis

Vacuum Phenomenon in Intervertebral Disk Space

= liberation of nitrogen gas from surrounding tissues into clefts with an abnormal nucleus or annulus attachment

Prevalence: in up to 20% of plain radiographs / in up to 50% of spinal CT in patients > age 40

Cause:

• Primary / secondary degeneration of nucleus pulposus

• Intraosseous herniation of disk (= Schmorl node)

• Spondylosis deformans (gas in annulus fibrosus)

• Adjacent vertebral metastatic disease with vertebral collapse

• Infection (extremely rare)

Intervertebral Disk Calcification

mnemonic: A DISC SO WHITE

• Amyloidosis, Acromegaly

• Degenerative

• Infection

• Spinal fusion

• CPPD

• Spondylitis ankylosing

• Ochronosis

• Wilson disease

• Hemochromatosis, Homocystinuria, Hyperparathyroidism

• Idiopathic skeletal hyperostosis

• Traumatic

• Etceteras: Gout and other causes of chondrocalcinosis

Intervertebral Disk Ossification

Associated with: fusion of vertebral bodies

• Ankylosing spondylitis

• Ochronosis

• Sequelae of trauma

• Sequelae of disk-space infection

• Degenerative disease

Schmorl = Cartilaginous Node

= superior / inferior intravertebral herniation of disk material through weakened area of vertebral endplate

Pathogenesis: disruption of cartilaginous plate of vertebral body left during regression of chorda dorsalis, ossification gaps, previous vascular channels

P.190

Cause:

• osseous: osteoporosis, osteomalacia, Paget disease, hyperparathyroidism, infection, neoplasm

• cartilaginous: intervertebral osteochondrosis, disk infection, juvenile kyphosis

concave defects at upper and lower vertebral endplates with sharp margins

MR:

• node of similar signal intensity as disk

• low signal intensity of rim

• associated with narrowed disk space

Mneumonic of DDx: SHOOT

• Scheuermann disease

• Hyperparathyroidism

• Osteoporosis

• Osteomalacia

• Trauma

Spinal cord

Most spinal cord neoplasms are malignant!

90 95% are classified as gliomas

Intramedullary Lesion

Prevalence: 4 10% of all CNS tumors; 20% of all intraspinal tumors in adults (35% in children)

• TUMOR

  • expansion of cord

  • heterogeneous signal on T2WI

  • cysts + necrosis

  • variable enhancement (vast majority with some enhancement)

  • primary:

    • Ependymoma (60% of all spinal cord tumors)

      • The most common glial tumor in adults

    • Astrocytoma (25%)

      • The most common intramedullary tumor in children

    • Hemangioblastoma (5%)

    • Oligodendroglioma (3%)

    • Epidermoid, dermoid, teratoma (1 2%)

    • Ganglioglioma (1%)

    • Lipoma (1%)

      Location:

      • cervical region: astrocytoma

      • thoracic region: teratoma-dermoid, astrocytoma

      • lumbar region: ependymoma, dermoid

  • metastatic: eg, malignant melanoma, breast, lung

• CYSTIC LESION

  • fluid isointense to CSF

  • smooth well-defined internal margins

  • thinned adjacent parenchyma

  • cord atrophy

  • no contrast enhancement

  • peritumoral cyst = syringomyelia

    • polar / satellite cysts = rostral / caudal cysts representing reactive dilatation of central canal

    • A higher location within spinal canal raises the likelihood of syrinx development

    • Prevalence: in 60% of all intramedullary tumors

      • Syringomyelia

      • Hydromyelia

      • Reactive cyst

  • tumoral cyst

    shows peripheral enhancement

    • Ganglioglioma (in 46%)

    • Astrocytoma (in 20%)

    • Ependymoma (in 3%)

    • Hemangioblastoma (2 4%)

• VASCULAR

  • Cord concussion = reversible local edema

  • Hemorrhagic contusion

  • Cord transection

  • AVM

• CHRONIC INFECTION

  • Sarcoid

  • Transverse myelitis

  • Multiple sclerosis

  mnemonic: I'M ASHAMED

  • Inflammation (multiple sclerosis, sarcoidosis, myelitis)

  • Medulloblastoma

  • Astrocytoma

  • Syringomyelia / hydromyelia

  • Hematoma, Hemangioblastoma

  • Arteriovenous malformation

  • Metastasis

  • Ependymoma

  • Dermoid

Intramedullary Neoplastic Lesion

• GLIAL NEOPLASM (90 95%)

  • Ependymoma (60%)

  • Astrocytoma (33%)

  • Ganglioglioma (1%)

• NONGLIAL NEOPLASM

  • highly vascular lesions:

    • Hemangioblastoma

    • Paraganglioma

  • rare lesions:

    • Metastasis

    • Lymphoma

    • Primitive neuroectodermal tumor

• USUALLY EXTRAMEDULLARY NEOPLASM

  • Intramedullary meningioma

  • Intramedullary schwannoma

Intramedullary Nonneoplastic Mass

• Epidermoid

• Congenital lipoma

• Posttraumatic pseudocyst

• Wegener granuloma

• Cavernous malformation

• Abscess

Intramedullary Nonneoplastic Lesion

Prevalence: 4%

no cord expansion

• Demyelinating disease

• Sarcoidosis

• Amyloid angiopathy

• Pseudotumor

P.191




• Dural arteriovenous fistula

• Cord infarction

• Chronic arachnoiditis

• Cystic myelomalacia

Cord Lesions

• INFLAMMATION

  • Multiple sclerosis

  • Acute disseminated encephalomyelitis

  • Acute transverse myelitis

    • involves half the cross-sectional area of cord

  • Lyme disease

  • Devic syndrome

• INFECTION

  • Cytomegalovirus

  • Progressive multifocal leukoencephalopathy

  • HIV

• VASCULAR

  • Anterior spinal artery infarct

    • affects central gray matter first

    • extends to anterior two-thirds of cord

  • Venous infarct / ischemia

    • starts centrally progressing centripetally

• NEOPLASM

Intradural Extramedullary Mass

• Nerve sheath tumor (35%)

• Meningioma (25%)

• Lipoma

• Dermoid

  commonly conus / cauda equina; associated with spinal dysraphism (1/3)

• Ependymoma

  commonly filum terminale; NO spinal dysraphism

• Metastasis

  • Drop metastases from CNS tumors

  • Metastases from outside CNS

• Arachnoid cyst

• Neurenteric cyst

• Hemangioblastoma

• Paraganglioma

mnemonic: MAMA N

• Metastasis

• Arachnoiditis

• Meningioma

• AVM, Arachnoid cyst

• Neurofibroma

Epidural Extramedullary Lesion

= EXTRADURAL LESIONS OF SPINE

arise from bone, fat, vessels, lymph nodes, extramedullary neural elements

Prevalence: 30% of all spinal tumors

• TUMOR

  • benign

    • Dermoid, epidermoid

    • Lipoma: over several segments

    • Fibroma

    • Neurinoma (with intradural component)

    • Meningioma (with intradural component)

    • Ganglioneuroblastoma, ganglioneuroma

  • malignant

    • Hodgkin disease

    • Lymphoma: most commonly in dorsal space

    • Metastasis: breast, lung most commonly from involved vertebrae without extension through dura

    • Paravertebral neuroblastoma

• DISK DISEASE

  • Bulging disk

  • Herniated nucleus pulposus

  • Sequestered nucleus pulposus

• BONE

  • Tumor of vertebra

  • Spinal stenosis

  • Spondylosis

• INFECTION: epidural abscess

• BLOOD: hematoma

• OTHERS: synovial cyst, arachnoid cyst, extradural lipomatosis, extramedullary hematopoiesis

mnemonic: MANDELIN

• Metastasis (drop mets from CNS tumor), Meningioma

• Arachnoiditis, Arachnoid cyst

• Neurofibroma

• Dermoid / epidermoid

• Ependymoma

• Lipoma

• Infection (TB, cysticercosis)

• Normal but tortuous roots

Cord Atrophy

• Multiple sclerosis

• Amyotrophic lateral sclerosis

• Cervical spondylosis

• Sequelae of trauma

• Ischemia

• Radiation therapy

• AVM of cord

Delayed Uptake of Water-Soluble Contrast in Cord Lesion

• Syringohydromyelia

• Cystic tumor of cord

• Osteomalacia

  exceedingly rare:

• Demyelinating disease

• Infection

• Infarction

Extraarachnoid Myelography

• SUBDURAL INJECTION

  • spinal cord, nerve roots, blood vessels not outlined

  • irregular filling defects

  • slow flow of contrast material

  • CSF pulsations diminished

  • contrast material pools at injection site within anterior / posterior compartments

• EPIDURAL INJECTION

  • contrast extravasation along nerve roots

  • contrast material lies near periphery of spinal canal

  • intraspinal structures are not well outlined

P.192

Musculoskeletal neurogenic tumors

• BENIGN NEUROGENIC TUMOR

  • Traumatic neuroma

  • Morton neuroma

  • Neural fibrolipoma

  • Nerve sheath ganglion

  • Benign peripheral nerve sheath tumors (PNST)

    • Schwannoma = Neurilemmoma

    • Neurofibroma: localized, diffuse

    • Plexiform neurofibroma

  • MALIGNANT NEUROGENIC NEOPLASM

    • = malignant peripheral nerve sheath tumor (MPNST)

Spinal fixation devices

Function:

• to restore anatomic alignment in fractures (fracture reduction)

• to stabilize degenerative disease

• to correct congenital deformities (scoliosis)

• to replace diseased / abnormal vertebrae (infection, tumor)

Posterior Fixation Devices

using paired / unpaired rods attached with

• Sublaminar wiring

  = passing a wire around lamina + rod

• Interspinous wiring

  = passing a wire through a hole in the spinous process; a Drummond button prevents the wire from pulling through the bone

• Subpars wiring

  = passing a wire around the pars interarticularis

• Laminar / sublaminar hooks

  used on rods for compression / distraction forces to be applied to pedicles / laminae

  • upgoing hook curves under lamina

  • downgoing hook curves over lamina

• Pedicle / transpedical screws

• Rods

  • Luque rod = straight / L-shaped smooth rod 6 8 mm in diameter

  • O-ring fixator, rhomboid-shaped bar, Luque rectangle, segmental rectangle = preshaped loop to form a flat rectangle

  • Harrington distraction rod

  • Harrington compression rod

  • Knodt rod = threaded distraction rod with a central fixed nut (turnbuckle) and opposing thread pattern

  • Cotrel-Dubousset rods = a pair of rods with a serrated surface connected by a cross-link with 4 laminar hooks / pedicle screws

• Plates

  • Roy-Camille plates

    = simple straight plates with round holes

  • Luque plates

    = long oval holes with clips encircling the plate

  • Steffee plates = straight plates with long slots

• Translaminar screw

  • = cancellous screws for single level fusion

• Percutaneous pinning

  • = (hollow) interference screws placed across disk level

Anterior Fixation Devices

• Dwyer device

  • = screws threaded into vertebral body over staples embedded into vertebral body connected by braided titanium wire; placed on convex side of spine

• Zielke device

  • = modified Dwyer system replacing cable with solid rod

• Kaneda device

  • = 2 curved vertebral plates with staples attached to vertebral bodies with screws, plates connected by 2 threaded rods attached to screw heads

• Dunn device

  • (similar to Kaneda device, discontinued)

Spinal Fixation Devices

P.193

Cotrel-Dubousset Rods and Pedicle Screws

P.194

Anatomy of Skull and Spine

Foramina of base of skull

on inner aspect of middle cranial fossa 3 foramina are oriented along an oblique line in the greater sphenoidal wing from anteromedial behind the superior orbital fissure to posterolateral

mnemonic: rotos

• foramen rotundum

• foramen ovale

• foramen spinosum

Foramen Rotundum

• = canal within greater sphenoid wing connecting middle cranial fossa + pterygopalatine fossa

  Location: inferior and lateral to superior orbital fissure

  Course: extends obliquely forward + slightly inferiorly in a sagittal direction parallel to superior orbital fissure

Contents:

• nerves: V₂ (maxillary nerve)

• (b) vessels:

  • artery of foramen rotundum

  • emissary vv.

best visualized by coronal CT

Foramen Ovale

• = canal connecting middle cranial fossa + infratemporal fossa

Location: medial aspect of sphenoid body, situated posterolateral to foramen rotundum (endocranial aspect) + at base of lateral pterygoid plate (exocranial aspect)

Contents:

• nerves:

  • V₃ (mandibular nerve)

  • lesser petrosal nerve (occasionally)

• vessels:

  • accessory meningeal artery

  • emissary vv.

Foramen Spinosum

Location: on greater sphenoid wing posterolateral to foramen ovale (endocranial aspect) + lateral to eustachian tube (exocranial aspect)

Contents:

• nerves:

  • recurrent meningeal branch of mandibular nerve

  • lesser superficial petrosal nerve

• vessels:

  • middle meningeal a.

  • middle meningeal v.

Foramen Lacerum

Fibrocartilage cover (occasionally), carotid artery rests on endocranial aspect of fibrocartilage

Location: at base of medial pterygoid plate

Contents: (inconstant)

• nerve: nerve of pterygoid canal (actually pierces cartilage)

• vessel: meningeal branch of ascending pharyngeal a.

Foramen Magnum

• Contents:

  • nerves:

    • medulla oblongata

    • cranial nerve XI (spinal accessory n.)

  • vessels:

    • vertebral a.

    • anterior spinal a.

    • posterior spinal a.

Pterygoid Canal

• = VIDIAN CANAL

• = within sphenoid body connecting pterygopalatine fossa anteriorly to foramen lacerum posteriorly

Location: at base of pterygoid plate below foramen rotundum

Contents:

• nerves: vidian nerve = nerve of pterygoid canal = continuation of greater superficial petrosal nerve (from cranial nerve VII) after its union with deep petrosal nerve

• vessel: vidian artery = artery of pterygoid canal = branch of terminal portion of internal maxillary a. arises in pterygopalatine fossa + passes through foramen lacerum posterior to Vidian n.

Hypoglossal Canal

= ANTERIOR CONDYLAR CANAL

Location: in posterior cranial fossa anteriorly above condyle starting above anterolateral part of foramen magnum, continuing in an anterolateral direction + exiting medial to jugular foramen

Contents:

• nerves: cranial nerve XII (hypoglossal nerve)

• vessels:

  • pharyngeal artery

  • branches of meningeal artery

Jugular Foramen

Location: at the posterior end of petro-occipital suture directly posterior to carotid orifice

• anterior part:

  • inferior petrosal sinus

  • meningeal branches of pharyngeal artery + occipital artery

• intermediate part:

  • cranial nerve IX (glossopharyngeal nerve)

  • cranial nerve X (vagus nerve)

  • cranial nerve XI (spinal accessory nerve)

• posterior part: internal jugular vein

Craniovertebral junction

Craniometry:

• LATERAL VIEW

  • Chamberlain line = line between posterior pole of hard palate + opisthion (= posterior margin of foramen magnum)

    P.195

    
    

    • tip of odontoid process usually lies below / tangent to Chamberlain line

    • tip of odontoid process may lie up to 1 6.6 mm above the Chamberlain line

  • McGregor line = line between posterior pole of hard palate + most caudal portion of occipital squamosal surface

    • Substitute to Chamberlain line if opisthion not visible

    • tip of odontoid <5 mm above this line

  • Wackenheim clivus baseline

    • = BASILAR LINE = clival line = line along clivus

    • usually falls tangent to posterior aspect of tip of odontoid process

  • Craniovertebral angle = clivus-canal angle

    • = angle formed by line along posterior surface of axis body and odontoid process + basilar line

    • ranges from 150 in flexion to 180 in extension

    • ventral spinal cord compression may occur at <150

  • Welcher basal angle

    • = formed by nasion-tuberculum line and tuberculum-basion line

    • angle averages 132 (should be <140 )

  • McRae line = line between anterior lip (= basion) to posterior lip (= opisthion) of foramen magnum

    • tip of odontoid below this line

      ANTEROPOSTERIOR VIEW (= open-mouth / odontoid view)

  • Atlantooccipital joint axis angle

    • = formed by lines drawn parallel to both atlanto-occipital joints

    • lines intersect at center of odontoid process

    • average angle of 125 (range of 124 to 127 )

  • Digastric line = line between incisurae mastoideae (origin of digastric muscles)

    • tip of odontoid below this line

      

      Skull Base Lines on Lateral View

      

      Open-Mouth Odontoid View

  • Bimastoid line = line connecting the tips of both mastoid processes

    • tip of odontoid <10 mm above this line

Normal dimensions for adults:

• [posterior axial line = vertical line drawn along posterior aspect of the subdental body of C2]

Basion-dens interval (in 95%)	<12 mm
Basion-posterior axial line interval (in 98%) posterior to dens	<12 mm
anterior to dens	<4 mm
Prevertebral soft tissues at C2	<6 mm
Anterior atlanto-dens interval	<2 mm
Lateral atlanto-dens interval (side-to-side)	<3 mm
Atlanto-occipital articulation	<2 mm
Atlantoaxial articulation	<3 mm

Normal Relationship of Craniovertebral Junction

(range of the two extreme normal positions of the basion is drawn in dashes)

P.196

Meninges of spinal cord

• PERIOSTEUM

  • = continuation of outer layer of cerebral dura mater

• EPIDURAL SPACE

  • = space between dura mater + bone containing rich plexus of epidural veins, lymphatic channels, connective tissue, fat

  • cervical + thoracic spine: spacious posteriorly, potential space anteriorly

    • normal thickness of epidural fat 3 6 mm at T7

  • lower lumbar + sacral spine: may occupy more than half of cross-sectional area

• DURA

  • = continuation of meningeal / inner layer of cerebral dura mater; ends at 2nd sacral vertebra + forms coccygeal ligament around filum terminale; sends tubular extensions around spinal nerves; is continuous with epineurium of peripheral nerves

    Attachment: at circumference of foramen magnum, bodies of 2nd + 3rd cervical vertebrae, posterior longitudinal ligament (by connective tissue strands)

  • SUBARACHNOID SPACE

    • = space between arachnoid and pia mater containing CSF, reaching as far lateral as spinal ganglia

    • dentate ligament partially divides CSF space into an anterior + posterior compartment extending from foramen magnum to 1st lumbar vertebra, is continuous with pia mater of cord medially + dura mater laterally (between exiting nerves)

    • dorsal subarachnoid septum connects the arachnoid to the pia mater (cribriform septum)

  • PIA MATER

    • = firm vascular membrane intimately adherent to spinal cord, blends with dura mater in intervertebral foramina around spinal ganglia, forms filum terminale, fuses with periosteum of 1st coccygeal segment

Meninges of Spinal Cord

Typical Cervical Vertebra

(cranial aspect)

Thoracic spine

• 12 load-bearing vertebrae

• posterior arch (= pedicles, laminae, facets, transverse processes) handles tensional forces

• vertebral bodies:

  • height of vertebrae anteriorly 2 3 mm less than posteriorly = mild kyphotic curvature

  • AP diameter: gradual increase from T1 to T12

  • transverse diameter: gradual increase from T3 to T12

Thoracolumbar spine (T11 L2)

• anterior column = anterior longitudinal ligament, anterior annulus fibrosus, anterior vertebral body

• middle column = posterior longitudinal ligament, posterior annulus fibrosus, posterior vertebral body margin

  • Integrity of the middle column is synonymous with stability!

• posterior column = posterior elements + ligaments

Transitional vertebra

• = vertebra retaining partial features of segments below and above; total number of vertebrae usually unchanged

  Prevalence: 20%

• incidental finding

• Location:

  • often at sacrococcygeal + lumbosacral junction

P.197




• sacralized L5 = L5 incorporated into sacrum

  

  Cross Sections through 5th Lumbar Vertebra

  

  Anatomy of Diskovertebral Junction

  anterior longitudinal ligament attaches to anterior surface of vertebral body; it is less adherent to intervertebral disk;

  posterior longitudinal ligament is applied to back of intervertebral disk and vertebral bodies

• lumbarized S1 = S1 incorporated into lumbar spine

• Cx: confusion over labeling / assignment of vertebral levels during treatment planning

Normal position of conus medullaris

• Vertebral bodies grow more quickly than spinal cord during fetal period of <19 weeks MA!

• No significant difference regardless of age!

• Inferior-most aspect of conus:

  L1 L2 level:	normal (range T12 to L3)
  L2 L3 or higher:	in 97.8%
  L3 level:	indeterminate (in 1.8%)
  L3 L4 / lower:	abnormal
  by 3 month:	above inferior endplate of L2 (in 98%)

  N.B.: If conus is at / below L3 level, a search should be made for tethering mass, bony spur, thick filum!

P.198

Joints and Ligaments of Occipito-Atlanto-Axial Region

P.199

Skull and Spine Disorders

Arachnoiditis

Etiology:	trauma, back surgery, meningitis, subarachnoid hemorrhage, pantopaque myelography (inflammatory effect potentiated by blood), idiopathic
Associated with:	syrinx

• Myelo:

  • blunting of nerve root sleeves

  • blocked nerve roots without cord displacement (2/3)

  • streaking + clumping of contrast

• CT:

  • fusion / clumping of nerve roots

  • intradural pseudomass

  • intradural cysts

  • empty thecal sac = featureless empty-looking sac with individual nerve roots adherent to wall (final stage)

Arachnoid Cyst of Spine

Location:

dorsal to cord in thoracic region

Site:

• extradural cyst secondary to congenital / acquired dural defect

• intradural secondary to congenital deficiency within arachnoid (= true arachnoid cyst) / adhesion from prior infection or trauma (= arachnoid loculation)

• oval sharply demarcated extramedullary mass

• immediate / delayed contrast filling depending upon size of opening between cyst + subarachnoid space

• local displacement + compression of spinal cord

• higher signal intensity than CSF (from relative lack of CSF pulsations)

Arachnoid Diverticulum

= widening of root sheath with arachnoid space occupying >50% of total transverse diameter of root + sheath together

Cause:	? congenital / traumatic, arachnoiditis, infection
Pathogenesis:	hydrostatic pressure of CSF scalloping of posterior margins of vertebral bodies myelographic contrast material fills diverticula

Arteriovenous Malformation of Spinal Cord

Classification:

• True intramedullary AVM

  • = nidus of abnormal intermediary arteriovenous structure with multiple shunts

    Age:	2nd 3rd decade
    Cx:	subarachnoid hemorrhage, paraplegia
    Prognosis:	poor (especially in midthoracic location)

  • Intradural arteriovenous fistula

    = single shunt between one / several medullary arteries + single perimedullary vein

  • Dural arteriovenous fistula

    = single shunt between meningeal arteries + intradural vein

  • Metameric angiomatosis

Atlantoaxial Rotary Fixation

• history of insignificant cervical spine trauma / upper respiratory tract infection

• limited painful neck motion

• head held in cock-robin position + inability to turn head atlanto-odontoid asymmetry (open mouth odontoid view):

  • decrease in atlanto-odontoid space + widening of lateral mass on side ipsilateral to rotation

  • increase in atlanto-odontoid space + narrowing of lateral mass on side contralateral to rotation

  atlantoaxial asymmetry remains constant with head turned into neutral position

• Types:

  • <3 mm anterior displacement of atlas on axis

  • 3 5 mm anterior displacement

  • >5 mm anterior displacement

  • posterior displacement of atlas on axis

• DDx: torticollis (atlantoaxial symmetry reverts to normal with head turned into neutral position)

Brachial Plexus Injury

• Erb-Duchenne: adduction injury affecting C5-6 (downward displacement of shoulder)

• Klumpke: abduction injury at C7, C8, T1 (arm stretched over head)

• pouchlike root sleeve at site of avulsion

• asymmetrical nerve roots

• contrast extravasation collecting in axilla

• metrizamide in neural foramina (CT myelography)

Caudal Regression Syndrome

• = SACRAL AGENESIS = CAUDAL DYSPLASIA SEQUENCE

• = midline closure defect of neural tube with a spectrum of anomalies including complete / partial agenesis of sacrum + lumbar vertebrae and pelvic deformity

Etiology:	disturbance of caudal mesoderm <4th week of gestation from toxic / infectious / ischemic insult
Prevalence:	1:7,500 births; 0.005 0.01% of population; in 0.1 1% of pregnancies of women with diabetes
Predisposed:	infants of diabetic mothers; risk increase by 200 400 times in women dependent on insulin 16 22% of children with sacral agenesis have mothers with diabetes mellitus

NOT associated with VATER syndrome!

• Musculoskeletal anomalies

  • @ Lower extremity

    • symptoms from minor muscle weakness to complete sensorimotor paralysis of both lower extremities

    • hip dislocation

    • hypoplasia of lower extremities

    • flexion contractures of lower extremities

    • foot deformities

  • @ Lumbosacral spine = SACRAL AGENESIS

    Spectrum:

    P.200

    
    

    Type 1 =	unilateral partial agenesis localized to sacrum / coccyx
    Type 2 =	bilateral partial symmetric defects of sacrum + iliosacral articulation
    Type 3 =	total sacral agenesis + iliolumbar articulation
    Type 4 =	total sacral agenesis + ilioilial fusion posteriorly

  • nonossification of lower spine

  • fusion of caudal-most 2 or 3 vertebrae

  • spina bifida (lipomyelomeningocele often not in combination with Arnold-Chiari malformation)

  • narrowing of spinal canal rostral to last intact vertebra

  • hypoplastic iliac wings

• Spinal cord anomalies

  • characteristic club- / wedge-shaped configuration of conus medullaris (hypoplasia of distal spinal cord)

  • tethered spinal cord

  • dural sac stenosis with high termination

  • spinal cord lipoma, teratoma, cauda equina cyst

  • syrinx

• Genitourinary anomalies

  • neurogenic bladder (if >2 segments are missing)s

  • malformed external genitalia

    • bilateral renal aplasia with pulmonary hypoplasia

    • + Potter facies

• Hindgut anomalies

  • lack of bowel control

  • anal atresia

• OB-US:

  • normal / imperforate anus

    • short crown-rump length in 1st trimester (diabetic embryopathy)

    • normal / mildly dilated urinary system

    • normal / increased amniotic fluid

    • 2 umbilical arteries

    • 2 hypoplastic nonfused lower extremities

    • sacral agenesis, absent vertebrae from lower thoracic / upper lumbar spine caudally

• N.B.: brain, proximal spine, and spinal cord are notably spared!

Sirenomelia

= fused lower extremities resembling a mermaid (siren)

Cause:

aberrant vessel that shunts blood from the high abdominal aorta to the umbilical cord (steal phenomenon) resulting in severe ischemia of caudal portion of fetus

Differences between Caudal Regression Syndrome (CRS) and Sirenomelia

	CRS	Sirenomelia
umbilical artery	two	one
lower limb	two hypoplastic	single / fused
renal anomaly	nonlethal	renal agenesis / severe dysgenesis
anus	imperforate / normal	absent
amniotic fluid	polyhydramnios / normal	oligohydramnios

NOT associated with maternal diabetes mellitus!

• pulmonary hypoplasia + Potter facies

• absence of anus

• absent genitalia

  • bilateral renal agenesis / dysgenesis (lethal)

  • marked oligohydramnios

  • single aberrant umbilical artery

  • two-vessel umbilical cord

  • single / fused lower extremity often with fewer leg bones than normal

  • sacral agenesis, absent pelvis, lumbosacral tail , lumbar rachischisis

Prognosis:

incompatible with life

Chordoma

Chordoma is the most common primary malignant tumor of the spine in adults excluding lymphoproliferative neoplasms!

Prevalence:	1:2,000,000; 1 2 4% of all primary malignant neoplasms of bone; 1% of all intracranial tumors
Etiology:	originates from embryonic remnants of notochord / ectopic cordal foci (notochord appears between 4th and 7th week of embryonic development, extends from Rathke pouch to coccyx and forms nucleus pulposus)
Age:	30 70 (mean, 50) years (peak age in 6th decade); M:F = 2:1; highly malignant in children
Path:	lobulated tumor contained within pseudocapsule
Histo: typical chordoma: cords + clusters of large bubblelike vacuolated (physaliferous) cells containing intracytoplasmic mucous droplets; abundant extracellular mucus deposition + areas of hemorrhage chondroid chordoma: cartilage instead of mucinous extracellular matrix
Location: 50% in sacrum 35% in clivus 15% in vertebrae other sites (5%) in mandible, maxilla, scapula amorphous calcification (50 75%) heterogeneous enhancement

• CT:

  • low-attenuation within soft-tissue mass (due to myxoid-type tissue)

  • higher attenuation fibrous pseudocapsule

• MR (modality of choice):

  • low to intermediate intensity on T1WI, occasionally hyperintense (due to high protein content):

    • heterogeneous internal texture due to calcification, necrosis, gelatinous mucoid collections

  • very high signal intensity on T2WI (due to physaliferous cells similar to nucleus pulposus with high water content)

• Angio:

  • prominent vascular stain

• NUC:

  • cold lesion on bone scan

  • no uptake on gallium scan

Metastases (in 5 43%) to:	liver, lung, regional lymph node, peritoneum, skin (late), heart
Prognosis:	almost 100% recurrence rate despite radical surgery

P.201

Sacrococcygeal Chordoma (50 70%)

Most common primary malignant sacral tumor;

2 4% of all malignant osseous neoplasms!

Peak age:

40 60 years; M:F = 2:1

• low back pain (70%)

• constipation / fecal incontinence

• rectal bleeding (42%)

• sciatica

• frequency, urgency, straining on micturition

• sacral mass (17%)

Location:

esp. in 4th + 5th sacral segment
presacral mass with average size of 10 cm extending
superiorly + inferiorly; rarely posterior location
displacement of rectum + bladder
solid tumor with cystic areas (in 50%)
osteolytic midline mass in sacrum + coccyx
amorphous peripheral calcifications (15 89%)
secondary bone sclerosis in tumor periphery (50%)
honeycomb pattern with trabeculations (10 15%)
may cross sacroiliac joint

Prognosis:	8 10 years average survival; 66% 5-year survival rate (adulthood)
DDx:	Giant cell tumor, plasmacytoma, lymphoma, metastatic adenocarcinoma, aneurysmal bone cyst, atypical hemangioma, chondrosarcoma, osteomyelitis, ependymoma

Sphenooccipital Chordoma (15 35%)

Age:

younger patient (peak age of 20 40 years); M:F - 1:1

• orbitofrontal headache

• visual disturbances, ptosis

• 6th nerve palsy / paraplegia

Location:

clivus, spheno-occipital synchondrosis
bone destruction (in 90%): clivus > sella > petrous bone > orbit > floor of middle cranial fossa > jugular fossa > atlas > foramen magnum
reactive bone sclerosis (rare)
calcifications / bone fragments (20 70%)
soft-tissue extension into nasopharynx (common), into sphenoid + ethmoid sinuses (occasionally), may reach nasal cavity + maxillary antrum
variable degree of enhancement

MR:

• large intraosseous mass extending into prepontine cistern, sphenoid sinus, middle cranial fossa, nasopharynx

• posterior displacement of brainstem

• usually isointense to brain / occasionally inhomogeneously hyperintense on T1WI

• hyperintense on T2WI

Prognosis:	4 5 years average survival
DDx:	meningioma, metastasis, plasmacytoma, giant cell tumor, sphenoid sinus cyst, nasopharyngeal carcinoma, chondrosarcoma

Vertebral / Spinal Chordoma (15 20%)

More aggressive than sacral / cranial chordomas

Age:

younger patient; M:F = 2:1

low back pain + radiculopathy

Location:

cervical (8% particularly C2), thoracic spine (4%), lumbar spine (3%)

Site:

midline centra sparing posterior elements; arising in perivertebral musculature (uncommon) solitary midline spinal mass tumor calcification in 30% sclerosis / ivory vertebra in 43 62% total destruction of vertebra, initially unaccompanied by collapse expansile growth:    violates disk space to involve adjacent bodies (10 14%) simulating infection    variable extension into epidural space of spine    exophytic anterior soft-tissue mass    expansion into neural foramen mimicking nerve sheath tumor

Cx:	complete spinal block
Prognosis:	4 5 years average survival
DDx:	metastasis, primary bone tumor, primary soft-tissue tumor, neuroma, meningioma

CSF Fistula

• Cause:

  • Trauma to skull base (most commonly) 2% of all head injuries develop CSF fistula

  • Tumor: especially those arising from pituitary gland

  • Congenital anomalies: encephalocele

• traumatic leak: usually unilateral; onset within 48 hours after trauma, usually scanty; resolve in 1 week

• nontraumatic leak: profuse flow; may persist for years

• anosmia (in 78% of trauma cases)

Location:	fractures through frontoethmoidal complex + middle cranial fossa (most commonly) high-resolution thin-section CT in coronal plane followed by rescanning after low-dose intrathecal contrast material instilled into lumbar subarachnoid space
Cx:	infection (in 25 50% of untreated cases)

Degenerative Disk Disease

• Therapeutic decision-making should be based on clinical assessment alone!

• There are no prognostic indicators on images in patients with acute lumbar radiculopathy!

• 35% of individuals without back trouble have abnormal findings (HNP, disk bulging, facet degeneration, spinal stenosis)

• Imaging is only justified in patients for whom surgery is considered!

Pathophysiology:

• loss of disk height leads to stress on facet joints + uncovertebral joints (= uncinate process), exaggerated joint motion with misalignment (= rostrocaudal subluxation) of facet joints, spine instability with arthritis, capsular hypertrophy, hypertrophy of posterior ligaments, facet fracture

Plain film:

• intervertebral osteochondrosis = disease of nucleus pulposus (desiccation = loss of disk water):

  • narrowing of disk space

  • vacuum disk phenomenon = radiolucent interspace accumulation of nitrogen gas at sites of negative pressure

  • disk calcification

  • bone sclerosis of adjacent vertebral bodies

P.202




• spondylosis deformans = degeneration of the outer fibers of the annulus fibrosus:

  • endplate osteophytosis growing initially horizontally + then vertically several millimeters from disko-vertebral junction (2 to displacement of nucleus pulposus in anterior + anterolateral direction producing traction on osseous attachment of annulus fibrosus [= fibers of Sharpey])

  • enlargement of uncinate processes

• osteoarthritis = degenerative disease of synovium-lined apophyseal / costovertebral joints:

  • degenerative spondylolisthesis

• cartilaginous node = intraosseous disk herniation

Myelography:

• delineation of thecal sac, spinal cord, exiting nerve roots

CT (accuracy >90%):

• facet joint disease (marginal sclerosis, joint narrowing, cyst formation, bony overgrowth)

• uncovertebral joint disease of cervical spine (osteophytes project into lateral spinal canal + neuroforamen)

MR:

• scalloping of cord (T2WI FSE / GRE images):

  anterior encroachment by disk / spondylosis posterior encroachment by ligamentum flavum hypertrophy

• loss of disk signal (due to desiccation secondary to a decrease in water-binding proteoglycans + increase in collagen within nucleus pulposus)

  grade 1 =	slight decrease in signal intensity of nucleus on T2WI
  grade 2 =	hypointense nucleus pulposus on T2WI + normal disk height
  grade 3 =	hypointense nucleus pulposus on T2WI + disk space narrowing

• annular tear:

  • (1) concentric tear - separation of annular lamellae

  • (2) transverse tear

  • (3) radial tear - crossing multiple annular lamellae with greater vertical dimension + more limited horizontal extent

  • diskogenic pain

    does not imply disk herniation

  Location:

  inferior / superior insertion at posterior margin of annulus

  • gap near middle of annulus

  • cleft of high signal intensity in a normally hypointense outer annulus on T2WI

  • contrast enhancement (secondary to granulation tissue / hyperemia / inflammation)

    

    Annular Tears of Disk

reduction in disk height (late):

• Schmorl's node

• moderate linear uniform enhancement on T1WI

• vacuum phenomenon with low signal on T1WI

endplate + marrow changes (Modic & DeRoos):

= linear signal alterations paralleling adjacent endplates

• Type I (4%) = edema pattern

  • Cause: replacement of bone marrow with hyperemic fibrovascular tissue + edema

  • in acute disk degeneration hypointense on T1WI + hyperintense on T2WI contrast-enhancement of marrow

• Type II (16%) = fatty marrow pattern

  • Cause: replacement of bone marrow with fat

  • in chronic disk degeneration

    hyperintense marrow signal on T1WI

    iso- to mildly hyperintense on T2WI

• Type III = bony sclerosis pattern

  • Cause: replacement of bone marrow with sclerotic bone

  • in chronic disk degeneration after a few years hypointense marrow signal on T1WI + T2WI

• juxtaarticular synovial cyst in posterolateral spinal canal (most frequently at L4-5):

  • smooth well-defined extradural mass adjacent to facet joint

  • variable signal pattern (due to serous, mucinous, gelatinous fluid components, air, hemorrhage)

  • hypointense perimeter (= fibrous capsule with calcium + hemosiderin) with contrast enhancement

NUC:

• SPECT imaging of vertebrae can aid in localizing increased uptake to vertebral bodies, posterior elements, etc.

• eccentrically placed increased uptake on either side of an intervertebral space (osteophytes, diskogenic sclerosis)

Sequelae:

• Disk bulging

• Disk herniation

• Spinal stenosis

• Facet joint disease

• Instability

  • dynamic slip >3 mm on flexion-extension

  • static slip >4.5 mm

  • traction spurs

  • vacuum phenomenon

DDx:

Idiopathic segmental sclerosis of vertebral body (middle-aged / young patient, hemispherical sclerosis in anteroinferior aspect of lower lumbar vertebrae with small osteolytic focus, only slight narrowing of intervertebral disk; unknown cause)

Modified Dallas Diskogram Classification

Grade	Description
0	contrast confined within nucleus pulposus
1	contrast extends to inner third of annulus
2	contrast extends to middle third of annulus
3	outer third of annulus + <30 of circumference
4	outer third of annulus + >30 of circumference
5	extension of contrast beyond annulus

P.203

Bulging Disk = Disk Bulge

= concentric smooth expansion of softened disk material beyond the confines of endplates with disk extension outward involving >50% of disk circumference

Cause:

weakened and lengthened but intact annulus fibrosus + posterior longitudinal ligament

Age:

common finding in individuals >40 years of age

Location:

L4-5, L5-S1, C5-6, C6-7
rounded symmetric defect localized to disk space level
smooth concave indentation of anterior thecal sac
encroachment on inferior portion of neuroforamen
accentuated by upright myelography

• MR:

  • nucleus pulposus hypointense on T1WI + hyperintense on T2WI (desiccation = water loss through degeneration + fibrosis)

Herniation of Nucleus Pulposus

= HNP = protrusion of disk material >3 mm beyond margins of adjacent vertebral endplates involving <50% of disk circumference

Cause:

rupture of annulus fibrosus with disk material confined within posterior longitudinal ligament 21% of asymptomatic population has disk herniation!

• local somatic spinal pain = sharp / aching, deep, localized

• centrifugal radiating pain = sharp, well-circumscribed, superficial, electric, confined to dermatome

• centrifugal referred pain = dull, ill-defined, deep or superficial, aching or boring, confined to somatome (= dermatome + myotome + sclerotome)

• Site:

  • posterolateral (49%) = weakest point along posterolateral margin of disk at lateral recess of spinal canal (posterior longitudinal ligament tightly adherent to posterior margins of disk)

  • posterocentral (8%)

  • bilateral (on both sides of posterior ligament)

  • lateral / foraminal (<10%)

  • extraforaminal = anterior (commonly overlooked) (29%)

  • intraosseous / vertical = Schmorl node (14%)

• Myelography:

  • sharply angular indentation on lateral aspect of thecal sac with extension above or below level of disk space (ipsilateral oblique projection best view)

  • asymmetry of posterior disk margin

  • double contour secondary to superimposed normal + abnormal side (horizontal beam lateral view)

  • narrowing of intervertebral disk space (most commonly a sign of disk degeneration)

    

    Disk Bulge & Herniations

    

    Location Descriptor for HNP on Axial Image

    

    Location Descriptor for HNP on Sagittal Image

  • deviation of nerve root / root sleeve

  • enlargement of nerve root secondary to edema ( trumpet sign )

  • amputated / truncated nerve root (nonfilling of root sleeve)

• MR:

  • herniated disk material of low signal intensity displaces the posterior longitudinal ligament and epidural fat of relative high signal intensity on T1WI

  • squeezed toothpaste effect = hourglass appearance of herniated disk at posterior disk margin on sagittal image

  • asymmetry of posterior disk margin on axial image

• Cx:

  • spinal stenosis

    mild = <1/3

    moderate = 1/3 to 2/3

    severe = >2/3

  • neuroforaminal stenosis

• Prognosis:

  conservative therapy reduces size of herniation by
  0 50%	in 11% of patients,
  50 75%	in 36% of patients,
  75 100%	in 46% of patients
  (secondary to growth of granulation tissue)

Broad-based Disk Protrusion

• triangular shape of herniation with a base wider than the radius of its depth

• 25 50% of disk circumference

P.204

Focal Disk Protrusion

• triangular shape of herniation with a base wider than the radius of its depth

• <25% of disk circumference

Disk Extrusion

• = prominent focal extension of disk material through the annulus with only an isthmus of connection to parent disk + intact / ruptured posterior longitudinal ligament

• mushroom-shaped herniation with base narrower than the radius of its depth

• toothpaste sign

Disk Sequestration

• = Free Fragment Herniation

• = complete separation of disk material from parent disk with rupture through posterior longitudinal ligament into epidural space

  • Missed free fragments are a common cause of failed back surgery!

  • migration superiorly / inferiorly away from disk space with compression of nerve root above / below level of disk herniation

  • disk material noted >9 mm away from intervertebral disk space = NO continuity

  • soft-tissue density with higher value than thecal sac

• DDx:

  • Postoperative scarring (retraction of thecal sac to side of surgery)

  • Epidural abscess

  • Epidural tumor

  • Tarlov cyst (dilated nerve root sleeve)

  • Conjoined nerve root (2 nerve roots arising from thecal sac simultaneously representing mass in ventrolateral aspect of spinal canal; normal variant in 1 3% of population)

Free Fragment Migration

• = separated disk material travels above / below intervertebral disk space

• continuity

Lateral Disk Herniation

Nerve compression occurs posterolaterally (here at L4-5); therefore an atypical lateral compression (here of L4 root) directs surgery to the wrong more cephalad level (L3-4 disk)

Cervical Disk Herniation

Peak age:

3rd 4th decade

• neck stiffness, muscle splinting

• dermatomic sensory loss

• weakness + muscle atrophy

• reflex loss

Sites:

C6-7 (69%); C5-6 (19%); C7-T1 (10%); C4-5 (2%)

• Sequelae:

  • compression of exiting nerve roots with pain radiating to shoulder, arm, hand

  • cord compression (spinal stenosis + massive disk rupture)

Thoracic Disk Herniation

Prevalence:	1% of all disk herniations
Sites: T11-12
calcification of disk fragments + parent disk (frequent)

Lumbar Disk Herniation

• sciatica =

  • stiffness in back

  • pain radiating down to thigh / calf / foot

  • paresthesia / weakness / reflex changes

• pain exaggerated by coughing, sneezing, physical activity + worse while sitting / straightening of leg

Sites:

L4-5 (35%) > L5/S1 (27%) > L3-4 (19%) > L2-3 (14%) > L1-2 (5%)

Dermoid of Spine

• = uni- / multilocular cystic tumor lined by squamous epithelium containing skin appendages (hair follicles, sweat glands, sebaceous glands)

• Cause:

  • congenital dermal rest / focal expansion of dermal sinus

  • acquired from implantation of viable dermal tissue (by spinal needle without trocar)

Prevalence:	1% of spinal cord tumors
Age at presentation:	<20 years; M:F = 1:1
May be associated with:	dermal sinus (in 20%)

• slowly progressive myelopathy

• acute onset of chemical meningitis (secondary to rupture of inflammatory cholesterol crystals from cyst into CSF)

Location:	lumbosacral (60%), cauda equina (20%)
Site:	extramedullary (60%), intramedullary (40%)    almost always complete spinal block on myelography    intensity of fat    occasionally hypointense on T1WI + hypodense on CT (secretions from sweat glands within tumor)    NO contrast enhancement    CT myelography facilitates detection

Diastematomyelia

• = SPLIT CORD = MYELOSCHISIS

• = sagittal division of spinal cord into two hemicords, each of which contains a central canal, one dorsal horn + one ventral horn

Etiology:

congenital malformation as a result of adhesions between ectoderm and endoderm; M:F = 1:3

P.205

• Path:

  • 2 hemicords each covered by layer of pia within single subarachnoid space + dural sac (60%); not accompanied by bony spur / fibrous band

  • 2 hemicords each with its own pial, subarachnoidal + dural sheath (40%); accompanied by fibrous band (in 25%), cartilaginous / bony spurs (in 75%)

Associated with:

myelomeningocele

• hypertrichosis, nevus, lipoma, dimple, hemangioma overlying the spine (26 81%)

• clubfoot (50%)

• muscle wasting, ankle weakness in one leg

Location:

lower thoracic / upper lumbar > upper thoracic > cervical spine

• sagittal cleft in spinal cord resulting in 2 asymmetric hemicords

• the 2 hemicords usually reunite caudal to cleft

• occasionally 2 coni medullaris

• eccentric central canal within both hemicords

• bony spur through center of spinal canal arising from posterior aspect of centra (<50%)

• thickened filum terminale >2 mm (>50%)

• tethered cord (>50%)

• low conus medullaris below L2 level (>75%)

• defect in thecal sac on myelogram

• @ Vertebrae

  • congenital scoliosis (50 75%)

    5% of patients with congenital scoliosis have diastematomyelia

  • spina bifida over multiple levels

  • anteroposterior narrowing of vertebral bodies

  • widening of interpediculate distance

  • narrowed disk space with hemivertebra, butterfly vertebra, block vertebra

  • fusion + thickening of adjacent laminae (90%)

  • (a) fusion to ipsilateral lamina at adjacent levels

  • (b) diagonal fusion to contralateral adjacent lamina = intersegmental laminar fusion

Cx:

progressive spinal cord dysfunction

Diskitis

Most common pediatric spine problem!

Etiology:

• Bloodborne bacterial invasion of vertebrae infecting disk via communicating vessels through endplate

  Vertebral osteomyelitis + diskitis may be the same entity!

• Invasive procedure: surgery, diskography, myelography, chemonucleolysis

Agents:

• pyogenic: Staphylococcus aureus (by far most common), gram-negative rods (in IV drug abusers / immunocompromised patients)

• nonpyogenic: tuberculosis, coccidioidomycosis TB has a propensity to extend beneath longitudinal ligaments with involvement of multiple vertebral levels

Pathogenesis: infection starts in disk (still vascularized in children) / in anterior inferior corner of vertebral body (in adults) with spread across disk to adjacent vertebral endplate

Age peak: 6 months to 4 years and 10 14 years; average age of 6 years at presentation

• over 2 4 weeks gradually progressing irritability, malaise, low-grade fever

• back / referred hip pain, limp

• refusal to bear weight

• elevated sedimentation rate, WBC count often normal

Location: L3-4, L4-5, unusual above T9; usually one disk space (occasionally 2) involved

Plain film (positive 2 4 weeks after onset of symptoms):

• decrease in disk space height (earliest sign) = intraosseous herniation of nucleus pulposus into vertebral body through weakened endplate

• indistinctness of adjacent endplates with destruction

• endplate sclerosis (during healing phase beginning anywhere from 8 weeks to 8 months after onset)

• bone fusion (after 6 months to 2 years)

CT:

• paravertebral inflammatory mass

• epidural soft-tissue extension with deformity of thecal sac

MR (preferred modality; 93% sensitive, 97% specific, 95% accurate):

• Very sensitive modality early on in disease process (especially enhanced T1WI + fat suppression)

• decreased marrow intensity on T1WI in two contiguous vertebrae

• in early stage preserved disk height with variable intensity on T2WI (often increased)

• in later stages loss of disk height with increased intensity on T2WI

NUC (41% sensitive, 93% specific, 68% accurate on Tc-99m MDP + Tc-99m WBC scans):

• positive before radiographs

• increased uptake in vertebral endplate adjacent to disk

• bone scan usually positive in adjacent vertebrae (until age 20) secondary to vascular supply via endplates; may be negative after age 20

Cx:	epidural / paravertebral abscess, kyphosis
Rx:	immobilization in body cast for ~4 weeks
DDx:	neoplastic disease (no breach of endplate, disk space often intact)

Postoperative Diskitis

Frequency:	0.75 2.8%
Organism:	Staphylococcus aureus; many times no organism recovered

• severe recurrent back pain 7 28 days after surgery accompanied by decreased back motion, muscle spasm, positive straight leg raising test

• fever (33%)

• wound infection (8%)

• persistently elevated / increasing ESR

• MR:

  • decreased signal intensity within disk + adjacent vertebral body marrow on T1WI

  • increased signal intensity in disk + adjacent marrow on T2WI often with obliteration of intranuclear cleft

  • contrast-enhancement of vertebral bone marrow disk space

P.206




• DDx: degenerative disk disease type I (no gadolinium-enhancement of disk)

Dislocation of Spine

Atlantooccipital Dislocation

= ATLANTOOCCIPITAL DISTRACTION INJURY

= disruption of tectorial membrane + paired alar ligaments resulting in grossly unstable injury

Diagnosis difficult to make!

Cause:	rapid deceleration with either hyperextension or hyperflexion
Age:	childhood (due to larger size of head relative to body, increased laxity of ligaments, horizontally oriented occipito-atlanto-axial joint, hypoplastic occipital condyles)
May be associated with:	occipital condyle fracture

• neurologic symptoms: range from respiratory arrest with quadriplegia to normal neurologic exam

• discomfort, stiffness

• Direction of dislocation / subluxation: anteriorly, posteriorly, superiorly

• Lateral radiograph:

  • Powers ratio (assessment for anterior subluxation) = BC/OA ratio >1 = ratio of distance between basion + spinolaminar line of C1 and the distance between posterior cortex of anterior tubercle of C1 + opisthion

  • basion-dens interval (BD) >12 mm without traction placed on head / neck

  • basion-axial interval >12 mm anterior / >4 mm posterior to posterior axial line (PAL)

  • >10 mm soft-tissue swelling anterior to C2 + pathologic convexity of soft tissues (80%)

CT:

• blood in region of tectorial membrane + alar ligaments

• condylar fracture fracture extension through hypoglossal canal (for cranial nerve XII)

• widening / incongruity of articulation between occipital condyles + lateral masses of C1

MR:

• fluid in articular capsules, nuchal ligament, interspinous ligament

Cx:

• Injury to caudal cranial nerves + upper 3 cervical nerves

• Epidural hematoma with brainstem compression + upper spinal cord injury

  

  Powers Ratio = BC/OA

  

  Additional Landmarks on Lateral Radiographfor the Assessment of Atlanto-occipital Dislocation

• Vasospasm / dissection of internal carotid and vertebral arteries

Prognosis: usually fatal

Atlantoaxial Distraction

• = injury to transverse atlantal ligament, alar ligament, tectorial membrane between C1 and C2, disruption of articular capsules

May be associated with:

type 1 dens fracture
   prevertebral soft-tissue swelling
   subluxation with enlargement of predental space to
   >5 mm in children <9 years of age
   >3 mm in adults
   widening of C1-C2 facets

• MR:

  • prevertebral, interspinous, nuchal ligament edema

  • facet widening / fluid

  • increased signal intensity of spinal cord

  • epidural hematoma

Dorsal Dermal Sinus

• = epithelium-lined dural tube extending from skin surface to intracanalicular space + frequently communicating with CNS / its coverings

Cause:	focal point of incomplete separation of cutaneous ectoderm from neural ectoderm during neurulation
Age:	encountered in early childhood 3rd decade; M:F = 1:1

• small midline dimple / pinpoint ostium

• hyperpigmented patch / hairy nevus / capillary angioma

Location:	lumbosacral (60%), occipital (25%), thoracic (10%), cervical (2%), sacrococcygeal (1%), ventral (8%)
Course:	in a craniad direction from skin level toward cord (due to ascension of cord relative to spinal canal during embryogenesis) P.207    50% of dorsal dermal sinuses end in dermoid / epidermoid cysts!    20 30% of dermoid cysts / dermoid tumors are associated with dermal sinus tracts!

• CT myelography (best modality to define intraspinal anatomy):

  • groove in upper surface of spinous process + lamina of vertebra

  • hypoplastic spinous process

  • single bifid spinous process

  • focal multilevel spina bifida

  • laminar defect

  • dorsal tenting of dura + arachnoid

  • sinus may terminate in conus medullaris / filum terminale / nerve root / fibrous nodule on dorsal aspect of cord / dermoid / epidermoid

  • nerve roots bound down to capsule of dermoid / epidermoid cyst

  • displacement / compression of cord by extramedullary dermoids / epidermoids

  • expansion of cord by intramedullary dermoids / epidermoids

  • clumping of nerve roots from adhesive arachnoiditis

Cx:

• Meningitis (bacterial / chemical)

• Subcutaneous / epidural / subdural / subarachnoid / subpial abscess (bacterial ascent)

  Dermal sinus accounts for up to 3% of spinal cord abscesses!

• Compression of neural structures

DDx:

pilonidal sinus / simple sacral dimple (no extension to neural structures)

Epidermoid of Spine

• = cystic tumor lined by a membrane composed of epidermal elements of skin

• Cause:

  • congenital dermal rest / focal expansion of dermal sinus

  • acquired from implantation of viable epidermal tissue (by spinal needle without trocar)

Prevalence:	1% of spinal cord tumors
Age at presentation:	3rd 5th decade; M > F
May be associated with:	dermal sinus

• slowly progressive myelopathy

• acute onset of chemical meningitis (secondary to rupture of inflammatory cholesterol crystals from cyst into CSF)

Location:

upper thoracic (17%), lower thoracic (26%), lumbosacral (22%), cauda equina (35%)

Site:

extramedullary (60%), intramedullary (40%)
   almost always complete spinal block on myelography
   displacement of spinal cord / nerve roots
   small tumors isointense to CSF
   NO contrast enhancement
   CT myelography facilitates detection

Epidural Abscess of Spine

Cause: diskitis, osteomyelitis, idiopathic

• back pain, radicular pain

• fever, leukocytosis

MR:

• thickening of epidural tissues (early stage):

  • isointense on T1WI

  • moderately hyperintense on T2WI

• liquefied abscess cavity oval-shaped on axial images:

  • hypointense on T1WI + hyperintense on T2WI

• cellulitis surrounding abscess:

  • best seen on with contrast enhancement (inflamed hypervascular tissue) + fat suppression

Epidural Hematoma of Spine

• Cause:

  • Trauma (71%)

    • vertebral fracture / dislocation

    • traumatic lumbar puncture

    • spine surgery (only in 0.1 3%)

  • Hypertension

  • Pregnancy

  • AVM

  • Vertebral hemangioma

  • Bleeding diathesis / anticoagulation / hemophilia

  • Idiopathic (45%)

Pathophysiology:	tearing of epidural veins
Mean age:	41 52 years

• acute radicular pain

• rapid onset of paraplegia

Location:	cervical > thoracic > lumbar spine
Site:	anterior / posterior to cord spinal cord compression high attenuation lesion on CT

• MR:

  • iso- / hyperintense on T1WI + hyperintense on T2WI compared to spinal cord (intensities quite variable)

  • strikingly low signal intensity on gradient-echo sequences (deoxyhemoglobin)

Rx:

conservative management

Fractures of Skull

Linear fracture (most common type) deeply black sharply defined line

DDx:

• vascular groove, esp. temporal artery (gray line, slightly sclerotic margin, branching like a tree, typical location (temporal artery projects behind dorsum sellae)

• suture

Depressed fracture

• often palpable

  bone-on-bone density

  Rx: surgery indicated if depression >3 5 mm (due to arachnoid tear / brain injury)

  N.B.: CT / MR mandatory to assess extent of underlying brain injury

• Skull-base fracture = basilar skull fracture

  • rhinorrhea (CSF)

  • otorrhea (CSF / hemotympanum)

  • raccoon eyes = periorbital ecchymosis

    pneumocephalus

    air in sulci

    air-fluid level in sinuses

Cx: infection, acute / delayed cranial nerve deficit, vascular laceration / dissection / occlusion / infarction

• Healing skull fracture

  • @ infants: in 3 6 months without a trace

  P.208

  
  

  • @ children (5 12 years): in 12 months

  • @ adults: in 2 3 years

    persistent lucency mimicking vascular groove

  • Cx: leptomeningeal cyst (= growing fracture)

LeFort Fracture

[Ren LeFort (1869 1951), French surgeon]

All LeFort fractures involve the pterygoid process!

• LeFort I = transverse (horizontal) maxillary fracture caused by blow to premaxilla

  Fracture line:

  • alveolar ridge

  • lateral aperture of nose

  • inferior wall of maxillary sinus

    detachment of alveolar process of maxilla

    teeth contained in detached fragment

• LeFort II = pyramidal fracture

  May be unilateral

  Fracture line: arch through

  • posterior alveolar ridge

  • medial orbital rim

  • across nasal bones

    separation of midportion of face

    floor of orbit + hard palate + nasal cavity involved

• LeFort III = craniofacial disjunction

  Fracture line: horizontal course through

  • nasofrontal suture

  • maxillofrontal suture

  • orbital wall

  • zygomatic arch

    separation of entire face from base of skull

Sphenoid Bone Fracture

Prevalence: involved in 15% of skull-base fractures

• CSF rhinorrhea / otorrhea

  

  Le Fort Fractures

• hemotympanum

• battle sign = mastoid region ecchymosis

• raccoon eyes = periorbital ecchymosis

• 7th / 8th nerve palsy

• muscular dysfunction: problems with ocular motility, mastication, speech, swallowing, eustachian tube function

  air-fluid level in sinuses + mastoid

  axial thin-slice high-resolution CT for best delineation of fractures

  water-soluble intrathecal contrast material for CSF fistula

Temporal Bone Fracture

Longitudinal Fracture of Temporal Bone (75%)

• = fracture parallel to the axis of petrous pyramid arising in squamosa of temporal bone through tegmen tympani, EAC (external auditory canal), middle ear, terminating in foramen lacerum

• bleeding from EAC (disruption of tympanic membrane)

• otorrhea (CSF leak with ruptured tympanic membrane; rare)

• conductive hearing loss (dislocation of auditory ossicles most commonly incus as the least anchored ossicle)

  • NO neurosensory hearing loss

• facial nerve palsy (10 20%) due to edema / fracture of facial canal near geniculate ganglion; frequent spontaneous recovery

  pneumocephalus

  herniation of temporal lobe

  incudostapedial joint dislocation (weakest joint):

  • ice cream (malleus) has fallen off the cone (incus) on direct coronal CT scan

  • fracture of molar tooth on direct sagittal CT scan

  mastoid air cells opaque / with air-fluid level

Plain film views:

Stenvers / Owens projection

P.209

Transverse Fracture of Temporal Bone (25%)

• = fracture perpendicular to axis of petrous pyramid originating in occipital bone extending anteriorly across the base of skull + across the petrous pyramid

• irreversible neurosensory hearing loss (fracture line across apex of IAC / labyrinthine capsule with injury to both parts of cranial nerve VIII)

• persistent vertigo

• facial (cranial nerve VII) nerve palsy in 50% (injury in IAC); less frequent spontaneous recovery because of disruption of nerve fibers

• rhinorrhea (CSF leak with intact tympanic membrane)

• bleeding into middle ear

Plain film views:

posteroanterior (transorbital) + Towne projection

Zygomaticomaxillary Fracture

• = TRIPOD FRACTURE = MALAR / ZYGOMATIC COMPLEX FRACTURE

Cause:

direct blow to malar eminence

• loss of sensibility of face below orbit

• deficient mastication

• double vision / ophthalmoplegia

• facial deformity

• Fracture line:

  • lateral wall of maxillary sinus

  • orbital rim close to infraorbital foramen

  • floor of orbit (d) zygomaticofrontal suture / zygomatic arch

Blowout Fracture

• = isolated fracture of orbital floor

Cause:

sudden direct blow to globe (ball or fist) with increase in intraorbital pressure transmitted to the weak orbital floor

• diplopia on upward gaze (entrapment of inferior rectus + inferior oblique muscles)

• enophthalmos

• facial anesthesia

Associated with:

fracture of the thin lamina papyracea (= medial orbital wall) in 20 50%
soft-tissue mass extending into maxillary sinus (= herniation of orbital fat)
complete opacification of maxillary sinus (edema + hemorrhage)
depression of orbital floor (= orbital process of maxilla)
posttraumatic atrophy of orbital fat leads to enophthalmos
opacification of adjacent ethmoid air cells
disruption of lacrimal duct

Fractures of Cervical Spine

Factors associated with higher risk of fracture:

• Glasgow Coma Score <14

• Neck tenderness

• Loss of consciousness

• Neurologic deficit

• Drug ingestion

• Specific mechanism of injury: motor vehicle accident, fall from a height >3 m

Indications for screening CT of cervical spine:

high-risk adult patients (= >5% pretest probability of injury) defined by:

• High-speed (>35 mph) motor vehicle accident

• Crash resulting in death at scene of accident

• Fall from height >3 m (10 feet)

• Significant closed head injury (intracranial hemorrhage seen on CT)

• Neurologic signs / symptoms referred to C-spine

• Pelvic / multiple extremity fractures

Frequency:

1 3% of all trauma cases;
C2, C6 > C5, C7 > C3, C4 > C1
   Cervical spine trauma accounts for 2/3 of all spinal cord injuries!

neurologic / spinal cord damage (39 50%)

Location:

• upper cervical spine = C1/2 (19 25%): atlas (4%), odontoid (6%)

• lower cervical spine = C3 7 (75 81%)

• cervicothoracic junction (9 18%)

• multiple noncontiguous spine fractures (15 20%)

Site:	vertebral arch (50%), vertebral body (30%), intervertebral disk (25%), posterior ligaments (16%), dens (14%), locked facets (12%), anterior ligament (2%)
Associated with injury to:	head (70%), thoracic spine (15%), lumbar spine (10%), thorax (35%), pelvis (15%), upper extremity (10%), lower extremity (30%)
N.B.:	5 8% of patients with fractures may have normal radiographs!    Most missed fractures involve C1 (8%), C2 (34%), C4 (12%), C6-7 (14%), occipital condyles    C7 T1 space not visualized in at least 26% of all trauma patients
Cx:	neurologic deterioration with delay in diagnosis

• HYPERFLEXION INJURY (46 79%)

  • Odontoid fracture

  • Simple wedge fracture (stable)

  • Flexion teardrop fracture = avulsion of anteroinferior corner by anterior ligament (unstable)

    Most severe + unstable injury of C-spine

    Location: C5, C6, C7

    • triangular fragment in soft tissues anterior to vertebral body

    • retrolisthesis

    • widening of facets

    • narrowing of spinal canal

    • mild kyphosis

  • Associated with: ligamentous tears, spinal cord compression

  • Anterior subluxation

  • Bilateral facet lock = interlocking of articular surfaces (unstable)

    • anterolisthesis of affected vertebra by 1/2 vertebral body width

    • mild focal kyphosis

    • soft-tissue swelling

    • no rotation

  • Anterior disk space narrowing

    P.210

    
    

    

    Atlas Fractures

    

    Axis Fractures

    

    Dens Fractures

    

    Dens Variants

  • Spinous process fracture = clay shoveler's fracture

    = sudden load on flexed spine with avulsion fracture of C6 / C7 / T1 (stable)

  • Flexion instability = isolated rupture of posterior ligaments

    • Dx may be missed without delayed flexion views

    • no fracture

    • interspinous widening

    • loss of facet parallelism

    • widening of posterior portion of disk

    • anterolisthesis >3 mm

    • focal kyphosis

• HYPEREXTENSION INJURY (20 38%)

  • High risk for neurologic deficit!

  • Radiographs may be completely normal!

  • Anteriorly widened disk space

  • Prevertebral swelling

  • Extension teardrop fracture

    Location: C2, C3

  • Neural arch fracture of C1 (stable = anterior ring + transverse ligament intact)

  • Subluxation (anterior / posterior)

  • Hangman's fracture (unstable)

    • = TRAUMATIC SPONDYLOLISTHESIS

    • bilateral pars fracture of C2

    • prevertebral soft-tissue swelling >5 mm at anterior-inferior margin of C2

    • anterior subluxation of C2 on C3:

      • disruption of C1 C2 spinolaminar line

      • disruption of C2 C3 posterior vertebral body line

    • avulsion of anteroinferior corner of C2 (rupture of anterior longitudinal ligament)

• FLEXION-ROTATION INJURY (12%)

  • Unilateral facet lock (oblique views!, stable)

    • anterolisthesis <1/4 vertebral body width

    • bow-tie sign = the 4 rotated facets on LAT view

    • decrease in spinolaminar space

    • rotation of spinous process (on AP view)

    • naked facet (on CT)

• VERTICAL COMPRESSION (4%)

  • Jefferson fracture

    [Sir Geoffrey Jefferson (1886 1961), neurosurgeon in Manchester, England]

    • comminuted burst fracture of ring of C1 (unstable) with uni- / bilateral ipsilateral anterior + posterior fractures

    P.211

    
    

    • lateral displacement of lateral masses (self-decompressing) on AP view

    (DDx: Pseudo-Jefferson fracture = lateral offset of lateral masses of atlas without fracture in fusion anomalies of anterior / posterior arches of C1, in children as lateral masses of atlas ossify earlier than C2)

• Burst fracture = intervertebral disk driven into vertebral body below (stable)

  • loss of posterior vertebral body height with several fragments:

    • sagittal fracture component extending to inferior endplate

    • retropulsed fragment from posterior superior margin in spinal canal

    • interpedicular widening

    • posterior element fracture

  Associated with: widening of apophyseal joints, fracture of posterior vertebral arches

• LATERAL FLEXION / SHEARING (4 6%)

  • Uncinate fracture

  • Isolated pillar fracture

  • Transverse process fracture

  • Lateral vertebral compression

Significant Signs of Cervical Vertebral Trauma

• most reliable + specific:

  • widening of interspinous space (43%)

  • widening of facet joint (39%)

  • displacement of prevertebral fat stripe (18%)

• reliable but nonspecific:

  • wide retropharyngeal space >7 mm (31%) (DDx: mediastinal hemorrhage of other cause, crying in children, S/P difficult intubation)

    

    Thoracic Spine Injury

• nonspecific:

  • loss of lordosis (63%)

  • anterolisthesis / retrolisthesis (36%)

  • kyphotic angulation (21%)

  • tracheal deviation (13%)

  • disk space: narrow (24%), wide (8%)

Atlas Fracture

Prevalence:	4% of cervical spine injuries
Site:	posterior arch, anterior arch, massa lateralis, Jefferson fracture
Associated with:	fractures of C7 (25%), C2 pedicle (15%), extraspinal fractures (58%)

Axis Fracture

Prevalence:	6% of cervical spine injuries
Associated with:	fractures of C1 in 8%
Type I =	avulsion of tip of odontoid (5 8%) difficult to detect
Type II =	fracture through base of dens (54 67%) Cx: nonunion Axial CT alone misses >50%!
Type III =	subdental fracture (30 33%) Prognosis: good
DDx:	os odontoideum, ossiculum terminale, hypoplasia of dens, aplasia of dens

Fractures of Thoracolumbar Spine

40% of all vertebral fractures that cause neurologic deficit; mostly complex (body + posterior elements involved)

Location: 2/3 at thoracolumbar junction

diastasis of apophyseal joints

disruption of interspinal ligament

retropulsion of body fragments into spinal canal

burst fragments at superior surface of body

Fracture of Upper Thoracic Spine (T1 to T10)

Frequency: in 3% of all blunt chest trauma

Types:

• compression / axial loading fracture (most common)

  • wedging of vertebral body

  • retropulsion of bone fragments

  • posttraumatic disk herniation

• burst fracture

  • associated fracture of posterior neural arch

  • comminuted retropulsed bone fragments

• sagittal slice fracture

  • vertebra above telescopes into vertebra below, displacing it laterally

• anterior / posterior dislocation

  • torn anterior / posterior longitudinal ligament

  • facet dislocation

  Relatively stable fractures due to rib cage + strong costovertebral ligaments + more horizontal orientation of facet joints!

  Only 51% detected on initial CXR!

  Often associated with: fracture of sternum

  widening of paraspinal lines

  mediastinal widening

  loss of height of vertebral body

  P.212

  
  

  obscuration of pedicle

  left apical cap

  deviation of nasogastric tube

Signs of Spinal Instability

• = inability to maintain normal associations between vertebral segments while under physiologic load

• displaced vertebra

• widening of interspinous / interlaminar distance

• facet dislocation

• disruption of posterior vertebral body line

Fracture of Thoracolumbar Junction (T11 to L2)

• = area of transition between a stiff + mobile segment of the spine

• neurologic deficit (in up to 40%)

• Classification based on injury to the middle column:

• Hyperflexion injury (most common)

  = compression of anterior column + distraction of posterior spinal elements

  • hyperflexion-compression fracture

    • loss of height of vertebral body anteriorly + laterally

    • focal kyphosis / scoliosis

    • fracture of anterosuperior endplate

  • flexion-rotation injury (unusual)

    • Very unstable!

    • catastrophic neurologic sequelae: paraplegia

    • subluxation / dislocation

    • widening of interspinous distance

    • fractures of lamina, transverse process, facets, adjacent ribs

  • shearing fracture-dislocation

    • = damage of all 3 columns secondary to horizontally impacting force

  • flexion-distraction injury: Chance fracture

• Hyperextension injury (extremely uncommon)

  • widened disk space anteriorly

  • posterior subluxation

  • vertebral anterior superior corner avulsion

  • posterior arch fracture

• Axial compression fracture

  • Unstable!

  • burst fracture with herniation of intervertebral disk through endplates + comminution of vertebral body

  • marked anterior vertebral body wedging

  • retropulsed bone fragment

  • increase in interpediculate distance

  • vertical fracture through vertebral body, pedicle, lamina

Chance Fracture

• = SEATBELT FRACTURE

• [George Quentin Chance, British radiologist in Manchester, England]

• Mechanism: shearing flexion-distraction injury (lap-type seatbelt injury in back-seat passengers)

• neurologic deficit infrequent (20%)

• Location: L2 or L3

  • horizontal splitting of spinous process, pedicles, laminae + superior portion of vertebral body

  • disruption of ligaments

  • distraction of intervertebral disk + facet joints

  • Fracture often unstable!

• Often associated with:

  • other bone injury

    • rib fractures along the course of diagonal strap; sternal fractures; clavicular fractures

  • soft-tissue injury

    • transverse tear of rectus abdominis muscle; anterior peritoneal tear; diaphragmatic rupture

  • vascular injury

    • mesenteric vascular tear; transection of common carotid artery; injury to internal carotid artery, subclavian artery, superior vena cava; thoracic aortic tear; abdominal aortic transection

  • visceral injury

    • perforation of jejunum + ileum > large intestine > duodenum (free intraperitoneal fluid in 100%, mesenteric infiltration in 88%, thickened bowel wall in 75%, extraluminal air in 56%); laceration / rupture of liver, spleen, kidneys, pancreas, distended urinary bladder; uterine injury

Chance Equivalent

• = purely ligamentous disruption leading to lumbar subluxation / dislocation

• mild widening of posterior aspect of affected disk space

• widened facet joints

• splaying of spinous processes = empty hole sign on AP view

Holdsworth Fracture

• [Sir Frank Wild Holdsworth (1904 1969), British pioneering orthopedist in rehabilitation of spinal injuries]

• Location: thoracolumbar junction

  • unstable spinal column fracture-dislocation with fracture through vertebral body + articular processes

  • rupture of posterior spinal ligaments

Seatbelt Injury

• = injury caused by three-point restraint type (combined lap and shoulder belt device)

• bruise in subcutaneous tissue + fat of anterior chest wall

• skin abrasions are associated with significant internal injuries (in 30%)

• @ Skeleton

  • sternum, ribs (along diagonal course of shoulder harness), clavicle, transverse processes of C7 or T1

• @ Cardiovascular

  • aortic transection, cardiac contusion, ventricular rupture, subclavian artery, SVC

• @ Airways

  • tracheal / laryngeal tear, diaphragmatic rupture

P.213

Transverse Process Fracture of Lumbar Spine

Cause:	direct trauma, violent lateral flexion-extension forces, avulsion of psoas muscle, Malgaigne fracture
Frequency:	7%
In 21 51% associated injury: genitourinary injury, hepatic + splenic laceration
Location:	L3 > L2 > L1 > L4 > L5; L:R = 2:1; multiple:single = 2:1; unilateral:bilateral = 20:1 vertical:horizontal (94%:6%) fractures associated lumbar burst / compression fracture Detection by conventional radiography in 40% only!
Prognosis:	minor and stable injury; 10% mortality

Sacral Fracture

Zone 1 =	fracture lateral to sacral foramina     significant neurologic deficit (uncommon)
Zone 2 =	fracture through 1 foramina     unilateral lumbar / sacral radiculopathy (rare)
Zone 3 =	fracture through central canal     significant bilateral neurologic damage (frequent): bowel / bladder incontinence
Cx:	chronic disability (in up to 50%)

Glioma of Spinal Cord

Astrocytoma of Spinal Cord

• Most common intramedullary neoplasm in children!

• 2nd most common intramedullary neoplasm in adults

Frequency:	30% of spinal cord tumors; 2nd in prevalence to ependymoma in adults
Mean age:	29 years; M:F = 58:42
Path:	ill-defined fusiform cord enlargement without cleavage plane / capsule
Histo:	hypercellularity with infiltrative growth along the scaffold of normal astrocytes, oligodendrocytes and axons; Grade I pilocytic astrocytoma (75%), usually most common in cerebellum Grade II low-grade fibrillary type Grade III anaplastic astrocytoma with necrosis (up to 25%) Grade IV glioblastoma multiforme with endothelial proliferation (0.2 1.5%)
Location:	thoracic cord (67%), cervical cord (49%), conus medullaris (3%); on average over 4 7 vertebral segments involved; holocord presentation (in up to 60% in children); often extending into lower brainstem
Site:	eccentric within spinal cord (57%) over pain + sensory deficit (54%) motor dysfunction (41%) gait abnormalities (27%) torticollis (27%)
Radiographs:    scoliosis (24%)    widened interpedicular distance    bone erosion
MR:    usually homogeneous extensive ill-defined cord tumor with expansion of spinal cord:       iso- to hypointense to cord on T1WI       hyperintense on T2WI       poorly defined margins    dilated veins on surface of cord    patchy irregular Gd-enhancement on MR    eccentric irregular tumor cysts + polar cysts + syrinx (common):       water-soluble myelographic contrast enters cystic space on delayed CT images    leptomeningeal spread (in 60% of glioblastoma multiforme)
Rx:	tumor debulking + radiation therapy
Prognosis:	95% 5-year survival in low-grade tumors; higher mortality rate than for ependymoma
DDx:	ependymoma (cap sign, central location, well defined, hemorrhage common, focal intense enhancement, predilection for conus)

Ependymoma of Spinal Cord

Most common intramedullary spinal neoplasm in adults!

Frequency:	40 60% of primary spinal cord tumors; 90% of primary tumors in the filum terminale
Mean age:	39 years; M:F = 57:43
Origin:	ependymal cells lining the central canal (62 76%)
Path:	symmetric cord expansion with displacement of neural tissue yielding a cleavage plane
Histo:	perivascular pseudorosettes; cystic degeneration (50%); hemorrhage at superior + inferior tumor margins
Subtypes:	cellular (most common), papillary, clear cell, tanycytic, myxopapillary (along filum terminale), melanotic
Location:	cervical cord alone (44%) / with extension into thoracic cord (23%); thoracic cord alone (26%); conus medullaris (7%); extends over several vertebral segments (on average 3.6 segments involved)
ectopic:	sacrococcygeal region, broad ligament of ovary (associated with spina bifida occulta [33%])
Site:	central within spinal cord long antecedent history (mean duration of 37 months) due to slow tumor growth:     back / neck pain (67%) = compression / interruption of central spinothalamic tracts first     sensory deficits (52%), motor weakness (46%)     bowel / bladder dysfunction (15%)
Metastases to:	lung, retroperitoneum, lymph nodes well-demarcated / diffusely infiltrating cord tumor associated with at least one cyst (in 78 84%):    polar cysts (62%) at cranial and caudal aspect of tumor, which do not contain malignant cells    tumoral cysts (4 50%), which may contain tumor    syringohydromyelia (9 50%)
Radiographs:    scoliosis (16%)    widening of spinal canal (11%):       scalloping of vertebral body       pedicle erosion, laminar thinning
Myelography:    enlarged cord with complete / partial block to flow of contrast material
CT:    iso- / slightly hyperattenuating cord mass    intense enhancement
MR:    iso- / hypointense (rarely hyperintense from hemorrhage) mass relative to spinal cord on T1WI    hyper- / isointense on T2WI     cap sign = extremely hypointense rim at the tumor poles on T2WI (in 20 33%) due to hemosiderin deposits from prior hemorrhage    cord edema (60%)    mostly intense homogeneous enhancement on Gd-enhanced MR (84%)    well-defined margins on contrast-enhanced images (89%)
Prognosis:	82% 5-year survival rate
DDx:	astrocytoma (pediatric tumor, eccentric location, ill defined, hemorrhage uncommon, patchy irregular enhancement)

P.214

Myxopapillary Ependymoma of Spinal Cord

= special variant of ependymoma of lower spinal cord

Prevalence:	13% of all spinal ependymomas; most common neoplasm of conus medullaris (83%)
Mean age:	35 years; M>F
Origin:	ependymal glia of filum terminale
Path:	heterogeneous tumor with generous mucin production
lower back / leg / sacral pain
weakness / sphincter dysfunction
Location:	conus medullaris, filum terminale; occasionally multiple (14 43%)    isointense on T1Wi + hyperintense on T2WI    occasionally hyperintense on T1WI + T2WI due to mucin content / hemorrhage    almost always contrast enhancing    occasionally large lytic area of bone destruction

Subependymoma of Spinal Cord

= variant of CNS ependymoma

Origin:	tanycytes [tanyos, Greek = stretch] that bridge pial + ependymal layers
Mean age:	42 years; M:F = 74:26
Histo:	sparsely dispersed ependymal cells among predominant fibrillar astrocytes
52 months mean duration of symptoms:     pain, sensory + motor dysfunction     atrophy of one / both distal upper extremities (83%)
Location:	ventricular system of brain, some in cervical cord    fusiform dilatation of spinal cord:       enhancing lesion with well-defined borders (50%)       nonenhancing lesion with diffuse symmetric cord enlargement    eccentrically located mass     edema

Ganglioglioma of Spinal Cord

• = ganglioglioneuroma = GANGLIONIC NEUROMA = neuroastrocytoma = neuroganglioma = GANGLIONIC GLIOMA = = neuroglioma = NEUROMA gangliocellulare

Prevalence:	0.4 6.2% of all CNS tumors; 1.1% of all spinal neoplasms
Mean age:	12 years; children > adults; M:F = 1:1
Histo:	mixture of irregularly oriented neoplastic mature neuronal elements (neurons / ganglion cells) + glial elements (neoplastic astrocytes), arranged in clusters = grade I or II lesions
Location:	cervical cord (48%), thoracic cord (22%), conus, holocord (average length of 8 vertebral segments); usually supratentorial (temporal lobe)
duration of symptoms between 1 month and 5 years scoliosis (44%), spinal remodeling (93%) due to relatively slow growth (rare in astrocytoma / ependymoma) eccentric small tumoral cysts (in 46%) calcifications (rare compared with intracranial tumor)
MR:    mixed tumor signal intensities on T1WI (in 84%)    tumor homogeneously hyperintense on T2WI    surrounding edema (less common than in ependymoma / astrocytoma)    patchy (65%) / no (15%) tumor enhancement    enhancement of pial surface (58%)
Cx:	malignant transformation (10%)
Prognosis:	slow growth; 89% 5-year and 83% 10-year survival rate; 27% recurrence rate

Hemangioblastoma of spine

= ANGIOBLASTOMA = angioreticuloma

Prevalence:	1 7.2% of all spinal cord tumors; mostly sporadic
Associated with:	von Hippel-Lindau disease (in 1/3)
Recommendation:	screening MR imaging of brain + spine in patients with von Hippel-Lindau syndrome
Age:	middle age; M:F = 1:1
Path:	nonglial highly vascular discrete nodular masses abutting leptomeninges with prominent dilated + tortuous vessels on posterior cord surface
Histo:	large pale stromal cells of unknown origin packed between blood vessels of varying sizes
Location:	intramedullary (75%), radicular (20%), intradural extramedullary (5%); thoracic cord (50%), cervical cord (40%); solitary in >80%, multiple lesions indicate von Hippel-Lindau syndrome + require screening of entire spine
Site:	subpial aspect of dorsal spine; may extend exophytically into subarachnoid / extradural space
mean duration of symptoms is 38 months:
sensory changes (39%): impaired proprioception
motor dysfunction (31%), pain (31%)
increased interpediculate distance (mass effect)
Angio:    highly vascular mass with dense prolonged blush    large draining veins form sinuous mass along posterior aspect of cord
MR:    iso- (50%) / hyperintense (25%) diffuse cord expansion on T1WI    hyperintense lesion with intermixed focal flow voids on T2WI:       curvilinear areas of signal voids P.215    cyst formation / syringohydromyelia (in up to 100%):       intratumoral cystic component (50 60%)       occasionally cystic mass with enhancing mural nodule (CLASSIC for cerebellar hemangioblastoma)       densely staining tumor nodule     surrounding edema and cap sign    well-demarcated Gd-enhancing mass
Cx:	intramedullary hemorrhage, hematomyelia, subarachnoid hemorrhage (rare)
DDx:	arteriovenous fistula (not well circumscribed, heterogeneous signal intensity)

Klippel-Feil Syndrome

• = brevicollis

• = synostosis of two / more cervical segments

• May be associated with:

  platybasia, syringomyelia, encephalocele, facial + cranial asymmetry, Sprengel deformity (25 40%), syndactyly, clubbed foot, hypoplastic lumbar vertebrae; renal anomalies in 50% (agenesis, dysgenesis, malrotation, duplication, renal ectopia); congenital heart disease in 5% (atrial septal defect, coarctation)

• clinical triad of

  • short neck

  • restriction of cervical motion

  • low posterior hairline

• deafness (30%)

• webbed neck

• Location: cervical spine

  • fusion of vertebral bodies and posterior elements

  • hemivertebrae

  • may have cervicothoracic / cervical / atlanto-occipital fusion

  • torticollis

  • scoliosis

  • rib fusion

  • Sprengel deformity (25 40%)

  • ear anomalies: absent auditory canal, microtia, deformed ossicles, underdevelopment of bony labyrinth

K mmell Disease

• = INTRAVERTEBRAL VACUUM PHENOMENON

• = delayed posttraumatic collapse of vertebral body

Cause:	ischemic necrosis weeks to months following an acute fracture
Pathophysiology:	intraosseous cleft forms due to a decrease in vertebral volume; low pressure within cleft allows accumulation of gas (principally nitrogen)
Age:	>50 years
Location:	most commonly at thoracolumbar junction    collapsed vertebral body    transverse linear / semilunar radiolucency located centrally within / adjacent to endplate    gas collection increases with extension + traction, decreases with flexion

Leptomeningeal Cyst

• = Growing fracture = loculation of CSF into / through skull

Prevalence:	1% of all pediatric skull fractures
Pathogenesis:	skull fracture with dural tear leads to arachnoid herniation into dural defect; CSF pulsations produce fracture diastasis + erosion of bone margins (apparent 2 3 months after injury)

skull defect with indistinct scalloped margins

CSF-density cyst adjacent to / in skull, may contain cerebral tissue

MR:

• cyst isointense with CSF + communicating with subarachnoid space

• area of encephalomalacia underlying fracture (frequent)

• intracranial tissue extending between edges of bone

Lipoma of Spine

• = partially encapsulated mass of fat + connective tissue in continuity with leptomeninges / spinal cord

• skin-coated subcutaneous back mass, occasionally associated with hemangiomatous / hairy lesion

• sensory deficiency, paresis, neurogenic bladder

• Types:

  • lipomyelomeningocele (84%)

  • fibrolipoma of filum terminale (12%)

  • intradural lipoma (4%)

    • Location: lumbosacral region

      Intradural lipomas + lipomyelomeningoceles represent 35% of skin-covered lumbosacral masses + 20 50% of occult spinal dysraphism!

Intradural Lipoma

= subpial juxtamedullary mass totally enclosed in intact dural sac

Prevalence:	<1% of primary intraspinal tumors
Etiology:	abnormal embryonic neurulation
Age peaks:	first 5 years of life (24%), 2nd + 3rd decade (55%), 5th decade (16%)
slow ascending mono- / paraparesis, spasticity, cutaneous sensory loss, defective deep sensation (with cervical + thoracic intradural lipoma)
flaccid paralysis of legs, sphincter dysfunction (with lumbosacral intradural lipoma)
overlying skin most often normal
elevation of protein in CSF (30%)
Location:	thoracic (30%) / cervicothoracic (24%) / cervical (12%)
Site:	dorsal aspect of cord (75%), lateral / anterolateral (25%)    spinal cord open in midline dorsally    lipoma in opening between lips of placode    exophytic component at upper / lower pole of lipoma    syringohydromyelia (2%)    focal enlargement of spinal canal adjacent neural foramina    narrow localized spina bifida

Lipomyelomeningocele

= lipoma tightly attached to exposed dorsal surface of neural placode blending with subcutaneous fat

P.216

Prevalence:	20% of skin-covered lumbosacral masses; up to 50% of occult spinal dysraphism
Age:	typically <6 months of age; M < F
semifluctuant lumbosacral mass with overlying skin intact
sensory loss in sacral dermatomes, motor loss, bladder dysfunction
foot deformities, leg pain
Location:	lumbosacral; longitudinal extension over entire length of spinal canal (in 7%)
Site:     lipoma dorsally continuous with subcutaneous fat     lipoma may extend upward within spinal canal external to dura (= epidural lipoma )     lipoma may enter central canal and extend rostrally (= intradural intramedullary lipoma )    deformed undulating spinal cord with dorsal cleft    tethered cord    ventral + dorsal nerve roots leave neural placode ventrally    dilated subarachnoid space

• US:

  • echogenic intraspinal mass adjacent to deformed spinal cord + continuous with slightly hypoechoic subcutaneous fat

• @ Vertebral changes

  • large spinal canal

  • erosion of vertebral body + pedicles

  • posterior scalloping of vertebral bodies (50%)

  • focal spina bifida

  • segmental anomalies / butterfly vertebra (up to 43%)

  • confluent sacral foramina / partial sacral agenesis (up to 50%)

Fibrolipoma of Filum Terminale

Prevalence:	6% of autopsies
asymptomatic
Location:	intradural filum, extradural filum, involvement of both portions thin linear fat-containing mass of filum terminale
Prognosis:	potential for development of symptoms of tethered cord

L ckensch del

• = CRANIOLACUNIA = lacunar skull

• = mesenchymal dysplasia of calvarial ossification (developmental disturbance)

Age:	present at birth
Associated with: meningocele / myelomeningocele / encephalocele spina bifida cleft palate Arnold-Chiari II malformation
normal intracranial pressure
Location:	particularly upper parietal area    honeycombed appearance about 2 cm in diameter (thinning of diploic space) premature closure of sutures (turricephaly / scaphocephaly)
Prognosis:	spontaneous regression within first 6 months of life
DDx:	(1) Convolutional impressions = digital markings (visible at 2 years, maximally apparent at 4 years, disappear by 8 years of age)
	(2) Hammered silver appearance of increased intracranial pressure

Lymphoma of Spinal cord

Prevalence:	3.3% of CNS lymphoma, 1% of all lymphomas
Mean age:	47 years; M<F
Histo:	monotonous collection of lymphocytes packed tightly into perivascular space; predominantly B-cell lymphocyte population; no necrosis
weakness, numbness, progressive difficulty in ambulation
Location:	cervical > thoracic > lumbar cord
Site:	in extradural compartment (most commonly)
MR:    mostly solitary, rarely multicentric    isointense relative to cord on T1WI    hypointense with cord on T2WI (related to high nuclear-to-cytoplasmic ratio)    extensive cord edema    hetero- / robust homogeneous enhancement    restricted diffusion (owing to high cellularity + reduced extracellular matrix)
Cx:	compression of cord due to narrowing of spinal canal
Rx:	initial response to steroids; radiation therapy results in rapid reduction in size + compressive effects

Meningeal Cyst

= abnormal dilatation of meninges within sacral canal / foramina

Prevalence:

5%

• remodeling erosion of sacral canal / foramen (due to CSF pulsations)

• thinned cortical margins

Perineural Sacral Cyst / Tarlov Cyst

• = dilated nerve-root sleeve as normal variant

Location:

posterior rootlets (S2 + S3 most common)

• neurologic symptoms if large

  cyst communicates freely with subarachnoid space

Sacral Meningeal / Arachnoid Cyst (less common)

• = OCCULT intrasacral MENINGOCELE

• usually asymptomatic

  cyst does not communicate with subarachnoid space

Meningioma of Spine

Prevalence:	25 45% of all spine tumors; 2 3% of pediatric spinal tumors; 12% of all meningiomas
Age:	>40 years + female (80%)
Location:	thoracic region (82%); cervical spine on anterior cord surface near foramen magnum (2nd most common location); 90% on lateral aspect
Site:	intradural extramedullary (50%); entirely epidural; intradural + epidural

• spinal cord / nerve root compression

  • bone erosion in <10%

  • scalloping of posterior aspect of vertebral body

  • widening of interpedicular distance

  • enlargement of intervertebral foramen

  • may calcify (not as readily as intracranial meningioma)

• CT:

  • solid smoothly marginated mass isodense with skeletal muscle

  • marked enhancement

P.217




• MR:

  • isointense with spinal cord on T1WI + T2WI

  • dural tail reflecting tumor spread / reactive changes

  • rapid + intense enhancement after Gd-DTPA

DDx:

nerve sheath tumor

Metastasis to Vertebra

Source: Metastatic tumors: lung, breast, prostate, kidney, lymphoma, malignant melanoma Primary tumor: multiple myeloma
Pathogenesis:	hematogenous spread to vertebral bodies (bones with greatest vascularity)
MR:    patchy multifocal relatively well-defined lesions    diminished signal on T1WI on background of high-signal appearance of marrow fat    increased signal on T2WI (except for blastic metastases with diminished T1 + T2 signals)    contrast enhancement on T1WI (majority)    pathologic compression fracture:       fracture only after all vertebral body fat replaced       hyperintense on diffusion-weighted images (DDx: hypointense benign osteoporotic fracture)
DDx:	(1) Infection (centered around disk space)
	(2) Primary vertebral tumor (rare in older patients, almost always benign in patients <21 years of age)

Metastases to Spinal Cord

Intramedullary Metastasis

Prevalence:	0.9 2.1% of CNS metastases (autoptic)
Origin:	lung (40 85%), breast (11%), melanoma (5%), renal cell (4%), colorectal (3%), lymphoma (3%), cerebellar medulloblastoma; 5% of unknown origin

• Spread:

  • common: hematogenous (via arterial supply) / direct extension from leptomeninges

  • rare: dissemination along central canal / extension along Batson venous plexus from retroperitoneal primary tumor / extension along perineural lymphatic ducts

• symptomatic for <1 month (in 75%):

  • motor weakness, bowel / bladder dysfunction (60%)

  • pain (70%), paresthesia (50%)

Location:

cervical (45%), thoracic (35%), lumbar cord (8%)

• Myelography (up to 40% undetected)

• MR:

  • mild cord expansion over several segments (average length of 2 3 vertebral segments)

  • central area of low signal intensity (mimicking syrinx) on T1WI

  • high signal intensity on T2WI (reflecting edema / tumor infiltration)

  • intense homogeneous enhancement

  • disproportionately large amount of surrounding edema

Prognosis:	66% die within 6 months
Rx:	radiation therapy, corticosteroids

Intradural Metastasis

• = Meningeal carcinomatosis of Spine

• round multifocal masses varying substantially in size from a few mm to >10 mm

• enlarged cord (from diffuse tumor coating of spinal cord) simulating an intramedullary lesion

• thickening of meninges (especially in lymphoma, breast cancer, prostate cancer)

• thickened + nodular matted nerve roots

• nodular + irregularly narrowed thecal sac

• Gd-DTPA enhancement (difficult to detect due to adjacent fat + enhancing epidural venous plexus)

Dx:	CSF analysis (more sensitive than imaging)
DDx:	moderate to severe meningitis, benign postoperative arachnoiditis, neurofibromatosis

Metastases from Outside CNS

• with subarachnoid hemorrhage:

  bronchogenic carcinoma, malignant melanoma, choriocarcinoma, hypernephroma

• others: breast (most common), lymphoma

  predominantly dorsal location

Drop Metastases

= CSF Seeding of Intracranial Neoplasms

Age:	occurs more frequently in pediatric age group than in adults
Location:	lumbosacral + dorsal thoracic spine (due to CSF flow / gravitation)
Site:	on spinal arachnoid / pia mater

CNS tumors causing drop metastases:

• Primitive neuroectodermal tumor

• Medulloblastoma: up to 33%

• Anaplastic glioma

• Ependymoma: after local recurrence, more common in infra- than supratentorial ependymomas

• Germinoma

• Pineoblastoma, pineocytoma

Less common:	choroid plexus carcinoma, teratoma, angioblastic meningioma
mnemonic:	MEGO TP

• Medulloblastoma

• Ependymoma

• Glioblastoma multiforme

• Oligodendroglioma

• Teratoma

• Pineoblastoma, PNET

Myelocystocele

• = syringocele

• = hydromyelic spinal cord + arachnoid herniated through posterior spina bifida; least common form of spinal dysraphism

May be associated with:

GI tract anomalies, GU tract anomalies

• cystic skin-covered mass over spine

• cloacal exstrophy (frequent)

Location:

lower spine > cervical > thoracic spine
   direct continuity of meningocele with subarachnoid space
   cyst communicating with widened central canal of spinal cord typically posteriorly + inferiorly to meningocele
   lordosis, scoliosis, partial sacral agenesis (common)

P.218

Myelomeningocele

• = sac covered by leptomeninges containing CSF + variable amount of neural tissue; herniated through a defect in the posterior / anterior elements of spine

Prevalence:	1:1,000 2,000 births (in Great Britain 1:200 births); twice as common in infants of mothers >35 years of age; Caucasians > Blacks > Orientals; most common congenital anomaly of CNS
Etiology:	localized defect of closure of caudal neuropore (usually closed by 28 days); persistence of neural placode causes derangement in the development of mesenchymal + ectodermal structures

• positive family history in 10%

• neural placode = reddish neural tissue in the middle of back made up of open spinal cord

• normal skin / cutaneous abnormality: pigmented nevus, abnormal distribution of hair, skin dimple, angioma, lipoma

• MS-AFP ( 2.5 S.D. over mean) permits detection in 80% (positive predictive value of 2 5%) if defect not covered by full skin thickness

Recurrence rate:	3 7% chance of NTD with previously affected sibling / in fetus of affected parent
Associated with: Hydrocephalus (70 90%): requiring ventriculoperitoneal shunt in 90% 25% of patients with hydrocephalus have spina bifida! Chiari II malformation (99%) Congenital / acquired kyphoscoliosis (90%) Vertebral anomalies (vertebral body fusion, hemivertebrae, cleft vertebrae, butterfly vertebrae) Diastematomyelia (20 46%): spinal cord split above (31%), below (25%), at the same level (22%) as the myelomeningocele Duplication of central canal (5%) cephalic to + at level of placode Hemimyelocele (10%) = two hemicords in separate dural tubes separated by fibrous / bony spur: one hemicord with myelomeningocele on one side of midline, one hemicord normal / with smaller myelomeningocele at a lower level impaired neurological function on side of hemimyelocele Hydromyelia (29 77%) cranial to placode as a result of disturbed CSF circulation Chromosomal anomalies (10 17%): trisomy 18, trisomy 13, triploidy, unbalanced translocation    In 20% no detectable associated anomalies! Tethering of spinal cord (70 90%) Arachnoid cyst (2%) due to developmental deficiency during formation of arachnoid / dura mater with a subdural location
Distribution:	thoracic (2%), thoracolumbar (32%), lumbar (22%), lumbosacral (44%)

Location:

• dorsal / posterior meningocele:

  • lumbosacral (70% below L2): may be associated with tethered cord, partial sacral agenesis

  • suboccipital

• anterior sacral meningocele = prolapse through anterior sacral bony defect; occasionally associated with neurofibromatosis type 1, Marfan syndrome, partial sacral agenesis, imperforate anus, anal stenosis, tethered spinal cord, GU tract / colonic anomalies; M:F = 1:4

• lateral thoracic meningocele through enlarged intervertebral foramen into extrapleural aspect of thorax; right > left side, in 10% bilateral; often associated with neurofibromatosis (85%) + sharply angled scoliosis convex to meningocele

  • expanded spinal canal

  • erosion of posterior surface of vertebral body

  • thinning of neural arch

  • enlarged neural foramen

• lateral lumbar meningocele through enlarged neural foramina into subcutaneous tissue / retroperitoneum; often associated with Marfan / Ehlers-Danlos syndrome / neurofibromatosis

  • expanded spinal canal

  • erosion of posterior surface of vertebral body

  • thinning of neural arch

  • enlarged neural foramen

• traumatic meningocele = avulsion of spinal nerve roots secondary to tear in meningeal root sheath; in C-spine after brachial plexus injury (most commonly)

  • small irregular arachnoid diverticulum with extension outside the spinal canal

• cranial meningocele = encephalocele

OB-US:

• detection rate of 85 90%; sensitivity dependent on GA (fetal spine may be adequately visualized after 16 20 weeks GA); false-negative rate of 24%

  • spinal level estimated by counting up from last sacral ossification center = S4 in 2nd trimester + S5 in 3rd trimester (79% accuracy for spinal level)

  • may have clubfoot / rocker-bottom foot

  • polyhydramnios

• @ Spine:

  • loss of dorsal epidermal integrity

  • soft-tissue mass protruding posteriorly + visualization of sac

  • widening of lumbar spine with fusiform enlargement of spinal canal:

    • splaying (= divergent position) of ossification centers of laminae with cup- / wedge-shaped pattern (in transverse plane = most important section for diagnosis)

    • absence of posterior line = posterior vertebral elements (in sagittal plane)

    • gross irregularity in parallelism of lines representing laminae of vertebrae (in coronal plane)

  • anomalies of segmentation / hemivertebrae (33%) with short-radius kyphoscoliosis

  • tethered cord (with lumbar / lumbosacral myelomeningocele)

• @ Head:

  • lemon sign = concave / linear frontal contour abnormality located at coronal suture strongly associated with spina bifida

  • banana sign

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Sonographic Cranial Signs of Myelomeningocele

Prevalence: in 96% of fetuses 24 weeks; in 91% of fetuses >24 weeks

nonvisualization of cerebellum

effaced cisterna magna (100% sensitivity)

• A normal cisterna magna is 3 10 mm deep and usually visualized in 97% at 15 25 weeks GA

BPD <5th percentile during 2nd trimester (65 79% sensitive)

HC <5th percentile (35% sensitivity)

ventriculomegaly (40 90%) with choroid plexus incompletely filling the ventricles (54 63% sensitivity) = dangling choroid on dependent side

Prevalence: in 44% of myelomeningoceles <24 weeks GA; in 94% of myelomeningo-celes during 3rd trimester

Plain films:

• bony defect in neural arch

• deformity + failure of fusion of lamina

• absent spinous process

• widened interpedicular distance

• widened spinal canal

Rx: (1) Possibly elective cesarean section at 36 38 weeks GA (may decrease risk of contaminating / rupturing the meningomyelocele sac)

(2) Repair within 48 hours

Postoperative complications:

• Postoperative tethering of spinal cord by placode / scar

• Constricting dural ring

• Cord compression by lipoma / dermoid / epidermoid cyst

• Ischemia from vascular compromise

• Syringohydromyelia

Prognosis:

• Mortality 15% by age 10 years

• Intelligence: IQ <80 (27%); IQ >100 (27%); learning disability (50%)

• Urinary incontinence: 85% achieve social continence (scheduled intermittent catheterization)

• Motor function: some deficit (100%); improvement after repair (37%)

• Hindbrain dysfunction associated with Chiari II malformation (32%)

• ventriculitis: 7% in initial repair within 48 hours, more common in delayed repair >48 hours

Neurenteric Cyst

= incomplete separation of foregut and notochord with persistence of canal of Kovalevski between yolk sac + notochord; cyst connected to meninges through midline defect

Incidence:	rarest of bronchopulmonary foregut malformations (pulmonary sequestration, bronchogenic cyst, enteric cyst)
Associated with:	neurofibromatosis; meningocele; spinal malformation (stalk connects cyst and neural canal; usually no stalk between cyst and esophagus)
Location:	anterior to spinal canal on mesenteric side of gut posterior mediastinal mass    air-fluid level (if communicating with GI tract through diaphragmatic defect)    spinal dysraphism at the same level:       midline cleft in centra (accommodates stalk)       anterior / posterior spina bifida       vertebral body anomalies: absent vertebra, butterfly vertebra, hemivertebra, scoliosis       diastematomyelia       thoracic myelomeningocele

Ossifying Fibroma

Peak incidence:	first 2 decades of life
Histo:	areas of osseous tissue intermixed with a highly cellular fibrous tissue
Sites:	maxilla > frontal > ethmoid bone > mandible (rarely seen elsewhere)    areas of increased + decreased attenuation    intact inner + outer table    slow-growing expansile lesion    usually unilateral + monostotic
DDx:	may be impossible to differentiate from fibrous dysplasia

Osteomyelitis of Vertebra

Prevalence: 2 10% of all cases of osteomyelitis

Cause:

• direct penetrating trauma (most common); following surgical removal of nucleus pulposus

• hematogenous: associated with urinary tract infections / following GU surgery / instrumentation; diabetes mellitus; drug abuse

Pathophysiology:	infection begins in low-flow end-vascular arcades adjacent to subchondral plate
Organism:	Staphylococcus aureus, Salmonella
Peak age:	5th 7th decade pain in back, neck, chest, abdomen, flank, hip neurologic deficit fever (most common presenting symptom), leukocytosis increased erythrocyte sedimentation rate positive blood / urine culture    disk space narrowing (earliest radiographic sign)    demineralization of adjacent vertebral endplates    bulging of paraspinal lines    tracer uptake in adjacent portions of two vertebral bodies decreased marrow signal on T1WI    iso- / hyperintense marrow signal on T2WI
Cx:	secondary infection of intervertebral disk is frequent
Rx:	>4 weeks course of IV antibiotics
DDx:	diskitis

P.220

Paraganglioma

Mean age:	46 years; M > F
Path:	soft encapsulated (75%) slightly hemorrhagic mass supplied by numerous feeding arteries
Histo:	chief cells + sustentacular cells surrounded by fibrovascular stroma; nests of chief cells in classic Zellballen configuration

• mean duration of symptoms for 4 years:

  • lower back pain, sciatica

Location:	cauda equina, filum terminale
Site:	intradural extramedullary compartment

CT:

• bone erosion of spine

MR:

• 3.3 (range, 1.5 10.0) cm average tumor size

• well-circumscribed mass isointense to cord on T1WI

• iso- to hyperintense on T2WI:

  • cap sign = low-signal intensity rim on T2WI from hemorrhage

  • salt-and-pepper appearance

• intense enhancement

• serpentine flow voids along surface + within tumor nodule

• syringohydromyelia

Angio:

• intense early blush persisting well into late arterial + early venous phase

Peripheral Nerve Sheath Tumor

Benign Peripheral Nerve Sheath Tumor

= (Benign PNST) = BENIGN TUMOR OF NERVE SHEATH = NEURINOMA

Histo:

contains cellular elements closely related to Schwann cell

• Schwann cell = cell that surrounds cranial, spinal, and peripheral nerves producing myelin sheath around axons thus providing mechanical protection, serving as a tract for nerve regeneration

• NOTE that myelin sheaths within brain substance are made by oligodendrocytes!

Plain film:

• fusiform mass delineated by surrounding fat

• soft-tissue and osseous overgrowth

• bone involvement + mineralization (osteoid / chondroid / amorphous) only in larger lesions

Angio:

• displacement of major vascular structures

• corkscrew-type vessels at upper / lower pole of tumor (= hypertrophy of nutrient nerve vasculature)

MR, CT:

• fusiform mass in a typical nerve distribution (94%):

  • entering + exiting nerve (intradural / extradural)

  • dumbbell shape with extension into enlarged neural foramen (intra- and extradural)

  • low attenuation (as low as 5 25 HU) due to

  • high lipid content of myelin from Schwann cells

  • entrapped fat

  • endoneural myxoid tissue with high water content (Antoni B areas)

  • isointense to muscle on T1WI + hyperintense to fat on T2WI

  • well-defined hyperdense / hypointense margins

• hypointense on T2WI in diffuse neurofibromas:

• target sign :

  • hypo- to isointense center + hyperintense periphery on T2WI (in 50 70%; almost PATHOGNOMONIC) = fibrocollagenous tissue centrally + myxomatous tissue peripherally

  DDx:

  atypical benign neural tumor, malignant neural tumor (absent target sign)

  • hyperdense center + hypodense periphery

• fascicular sign = multiple small ringlike structures with peripheral higher signal intensity on T2WI

• split-fat sign = rim of fat surrounding mass suggests a tumor origin in the intermuscular space

• marked uniform enhancement (most helpful for intradural lesions)

• muscle atrophy with striated increased fat content (in 23%)

Ga-67 scintigraphy:

• significant uptake in malignant PNST

Schwannoma = Neurilemmoma

= usually solitary well-encapsulated benign slowly growing neoplasm arising from Schwann cells resulting in eccentric displacement of nerve fibers

Nerve root NOT incorporated

Prevalence:	5 10% of all benign soft-tissue tumors
Age:	20 30 years
Path:	fusiform mass entering + exiting the nerve surrounded by a true capsule of epineurium; mass exophytic to involved nerve with nerve fibers splayed about the neoplasm in large nerves
Histo:	S-100 protein positive

• cellular component (Antoni type A tissue):

  more organized area composed of densely packed cellular spindle cells arranged in short bundles / interlacing fascicles

  Location:

  posterior mediastinum, retroperitoneum, 25% of extremity lesions

  hypointense on T2WI

• myxoid component (Antoni type B tissue):

  • less organized loosely arranged area of hypocellular myxoid tissue with high water content

  • hyperintense on T2WI

• ancient schwannoma: degenerative changes of cyst formation, calcification, hemorrhage, fibrosis

Location:

• extracranial: neck, flexor surfaces of upper + lower extremities, posterior mediastinum, retroperitoneum

  Site: ulnar n., peroneal n.

  Usually solitary, but in 5% associated with neurofibromatosis type 1 (= >2 schwannomas / one plexiform neurofibroma)

• spine

  Site: spinal and sympathetic nerve roots; most common in lower thoracic + lumbar spine

• intracranial: mostly from sensory nerves, vestibulocochlear (VIII) cranial nerve (most common) > trigeminal (V) cranial nerve (2nd most common) > VII

  P.221

  
  

  Usually sporadic tumor, but 5 20% of patients with solitary intracranial schwannomas have neurofibromatosis type 2!

• painless, fairly mobile mass

• neurologic symptoms

  solitary fusiform well-encapsulated <5 cm lesion slow growth

MR:

• well-delineated mass of intermediate signal intensity on T1WI

• heterogeneous mass of moderate hyperintensity on T2WI:

  • hypointense foci centrally related to dense collagen + Schwann cells

  • frequently low-signal-intensity rim (= capsule)

• peritumoral edema in 33%

• zones of fluid signal = cystic degeneration

• homo- / heterogeneous (33%) enhancement

DDx:	may appear similar to meningioma
Rx:	excision (affected nerve usually separable from neoplasm after incision of epineurium)

Neurofibroma

= usually multiple often infiltrative tumors of nerve sheath separating nerve fibers resulting in fusiform enlargement of nerve

Prevalence:	5% of all benign soft-tissue tumors
Histo:	swirls of neuronal elements containing Schwann cells, nerve fibers, fibroblasts, collagen in a myxoid / mucinous matrix
Association:	HALLMARK lesion of NF1 (= neurofibromatosis type 1)
Age:	20 30 years; M:F = 1:1    Malignant transformation exceedingly rare!    The spinal neurofibroma is rarely sporadic and usually a sign of type 1 neurofibromatosis!    Only 10% of patients with neurofibromas have von Recklinghausen disease!
Location:	skin, soft tissues, viscera; any level, but particularly cervical

• peripheral nerves

  nonencapsulated well-circumscribed fusiform mass of peripheral nerves

• intradural extramedullary mass

  • well-defined mass of dumbbell configuration (= intradural + extradural component, which extends through neural foramen)

  • widening of intervertebral foramen + erosion of pedicles

  • scalloping of vertebral bodies

  • hypodense (CHARACTERISTIC) approaching water density / isodense to skeletal muscle

  • usually NO contrast enhancement

MR:

• homogeneous mass isointense to cord / muscle on T1WI

• slightly hyperintense tumor on T2WI compared with surrounding fat (due to myxoid matrix / cystic degeneration)

• target sign = low signal-intensity center on T2WI (due to collagen + condensed Schwann cells) in 70% of extracranial neurofibromas

• ringlike enhancement of areas of low T2 signal (= complex fascicular arrangement)

• muscular atrophy

DDx:	conjoined nerve root sleeve
Rx:	surgical resection with sacrifice of nerve (tumor not separable from normal nerve)

Localized Neurofibroma

Prevalence:	90% of all neurofibromas
Path:	fusiform tumor, often remaining within epineurium as a true capsule
Histo:	interlacing fascicles of wavy elongated cells containing abundant amounts of collagen
Location:	affecting primarily superficial cutaneous nerves, occasionally deep-seated larger nerves

mostly solitary slow-growing lesion <5 cm in size

Diffuse Neurofibroma

Age:	children + young adults
Path:	poorly defined lesion within subcutaneous fat, infiltrating along connective tissue septa, inseparable from normal nerve tissue
Histo:	very uniform prominent fibrillary collagen
Location:	most frequently in subcutaneous tissues of head + neck

plaquelike elevation of skin with thickening of entire subcutis

• isolated lesion in 90% unassociated with NF1

• always indistinct infiltrative margins due to subcutaneous spread along connective tissue septa

Plexiform Neurofibroma

= involvement of a long segment of nerve + branches extending into adjacent muscle, fat, subcutaneous tissue

Location:

nerve plexus / multiple fascicles in a medium- to large-sized nerve

= PATHOGNOMONIC of neurofibromatosis type 1

serpentine bag of worms appearance = tortuous tangles / fusiform enlargement of a branching peripheral nerve

ropelike mass involving nonbranching nerve

reticulated linear branching pattern within subcutaneous tissue

Cx:

potential for malignant transformation to malignant peripheral nerve sheath tumor

Malignant Peripheral Nerve Sheath Tumor

= (MPNST) Malignant TUMOR OF Nerve Sheath = Neurofibrosarcoma = Malignant schwannoma = Neurogenic Spindle Cell Sarcoma

Prevalence:	5 10% of all soft-tissue sarcomas; 4 5% lifetime risk in NF1
Age:	20 50 years (mean, 26 years); M:F = 8:1
Associated with:	neurofibromatosis type 1 (in 25 70%), radiation therapy (in 11% of all malignant PNSTs after a latent period of 10 20 years)
Histo:	tumor cells arranged in fascicles resembling fibrosarcoma; additional heterotopic foci with mature cartilage and bone, rhabdomyosarcoma elements, glandular and epithelial components (in 10 15%)

P.222

• pain, motor weakness, sensory deficits in extremity

• clinically silent tumors in abdomen + retroperitoneum

Location:	paraspinal region of abdomen (sciatic n., sacral plexus, brachial plexus)
Metastases:	lung, bone, pleura, retroperitoneum (60%); regional lymph nodes (9%)    fusiform mass with entering + exiting nerve    frequently indistinct margins    sudden increase in size of a previously stable neurofibroma    frequently areas of hemorrhage + necrosis
Rx:	resection + adjuvant chemo- and radiation therapy with local recurrence in 40%
Prognosis:	highly aggressive tumor with a 44% 5-year survival rate

Primitive Neuroectodermal Tumor of Spinal Cord

Prevalence:	20 cases reported in literature
Location:	spinal cord, intradural-extramedullary compartment, extradural compartment
Age:	more common in adults than children; M:F = 6:4
Histo:	small round blue cells with hyperchromatic nuclei + scanty cytoplasm, frequent mitoses
weakness, paresthesia, gait disturbance, pain
Spread:	throughout CSF space into cranium, lung, bone, lymph node T1 and T2 prolongation
Prognosis:	in >50% death within 2 years

Sacrococcygeal Teratoma

Prevalence: 1:40,000 livebirths; type I + II (80%); most common congenital solid tumor in the newborn; M:F = 1:4

Pathogenesis:

• growth of residual primitive pluripotential cells derived from the primitive streak + knot (Hensen node) of very early embryonic development

• attempt at twinning

  • increased prevalence of twins in family

Histo:

• Mature teratoma (55 75%) with elements from glia, bowel, pancreas, bronchial mucosa, skin appendages, striated + smooth muscle, bowel loops, bone components (metacarpal bones + digits), well-formed teeth, choroid plexus structures (production of CSF)

  • MATURE TERATOMA = benign tumor composed of tissues foreign to the anatomic site in which they arise, usually containing tissues from at least 2 germ cell layers

• Immature teratoma (11 28%): admixed with primitive neuroepithelial / renal tissue

  • IMMATURE TERATOMA = benign teratoma with embryonic elements

• Malignant germ cell tumor

  • mixed malignant teratoma (7 17%): elements of endodermal sinus tumor (= yolk sac tumor) + either form of teratoma

  • pure endodermal sinus tumor (rare)

  • seminoma (dysgerminoma), embryonal carcinoma, choriocarcinoma (extremely rare)

Metastases to:

lung, bone, lymph nodes (inguinal, retroperitoneal), liver, brain

Age:

50 70% during first few days of life; 80% by 6 months of age; <10% >2 years of age; rare in adulthood; M:F = 1:4

Classification (Altman):

• Type I predominantly external lesion covered by skin with only minimal presacral component (47%)

• Type II predominantly external tumor with significant presacral component (35%)

• Type III predominantly sacral component + external extension (8%)

• Type IV presacral tumor with no external component (10%)

Associated with: other congenital anomalies (in 18%):

• musculoskeletal (5 16%): spinal dysraphism, sacral agenesis, dislocation of hip

• renal anomalies: hydronephrosis, renal cystic dysplasia, Potter syndrome

• GI tract: imperforate anus, gastroschisis, constipation

• fetal hydrops (due to high-output cardiac failure)

• placentomegaly (due to fetal hydrops)

• curvilinear sacrococcygeal defect (rare autosomal dominant inheritance with equal sex incidence, low malignant potential, absence of calcifications) + anorectal stenosis / atresia, vesicoureteral reflux

• AFP elevated with mixed malignant teratoma + endodermal sinus tumor (CAVE: fetal + newborn serum contains AFP, which does not reach adult levels until about 8 months of age)

• premature labor (due to polyhydramnios + large mass)

• uterus large for dates

• radicular pain, constipation, urinary frequency / incontinence

Plain film:

• amorphous, punctate, spiculated calcifications, possibly resembling bone (36 50%); suggestive of benign tumor

• soft-tissue mass in pelvis protruding anteriorly + inferiorly

BE:

• anterosuperior displacement of rectum

• luminal constriction

IVP:

• displacement of bladder anterosuperiorly

• development of bladder neck obstruction

Myelography:

• intraspinal component may be present

Angio:

• neovascularity (arterial supply by middle + lateral sacral + gluteal branches of internal iliac artery, branches of profunda femoris artery)

• enlargement of feeding vessels

• arterial encasement

• arteriovenous shunting

• early venous filling with serpiginous dilated tumor veins

US / CT:

• solid (25%) / mixed (60%) / cystic (15%) sacral mass

P.223




• 1 30 cm (average size of 8 cm) in diameter

• polyhydramnios (2/3)

• oligohydramnios, fetal hydronephrosis, fetal hydrops with ascites, pleural effusions, skin edema, placentomegaly are poor prognostic factors

MR:

• lobulated + sharply demarcated tumor extremely heterogeneous on T1WI as a result of high signal from fat, intermediate signal from soft tissue, low signal from calcium

• best modality to detect spinal canal invasion

Prognosis:	prevalence of malignant germ cell tumors increases with patient's age    predominantly fatty tissue tumors are usually benign hemorrhage / necrosis is suggestive of malignancy cystic lesions are less likely malignant    sacral destruction indicates malignancy    patients >2 months of age have a malignant tumor with a 50 90% probability
Cx:	(1) dystocia in 6 13% (2) massive intratumoral hemorrhage (3) fetal death in utero / stillbirth
Rx:	1. Complete tumor resection + coccygectomy + reconstruction of pelvic floor: up to 37% recurrence rate, esp. without coccygectomy 2. Multiagent chemotherapy (in malignancy) with long-term survival rate of 50%
DDx:	(1) Myelomeningocele (superior to sacrococcygeal region, not septated, axial bone changes) (2) Rectal duplication, anterior meningocele (purely cystic) (3) Hemangioma, lymphangioma, lipomeningocele, lipoma, epidermal cyst, chordoma, sarcoma, ependymoma, neuroblastoma

Scheuermann Disease

= SPINAL OSTEOCHONDROSIS = KYPHOSIS DORSALIS juvenilis = VERTEBRAL EPIPHYSITIS

= disorder consisting of vertebral wedging + endplate irregularity + narrowing of intervertebral disk space

Prevalence:	in 31% of male + 21% of female patients with back pain
Age:	onset at puberty
Location:	lower thoracic / upper lumbar vertebrae; in mild cases limited to 3 4 vertebral bodies anterior wedging of vertebral body of >5 increased anteroposterior diameter of vertebral body slight narrowing of disk space kyphosis of >40 / loss of lordosis; scoliosis Schmorl nodes (intravertebral herniation of nucleus pulposus into vertebral body) = depression in contour of endplate in posterior half of vertebral body; found in up to 30% of adolescents + young adults flattened area in superior surface of epiphyseal ring anteriorly = avulsion fracture of ring apophysis due to migration of nucleus pulposus through weak point between ring apophysis + vertebral endplate (fusion of ring apophysis usually occurs at about 18 years of age) detached epiphyseal ring anteriorly
DDx:	(1) Developmental notching of anterior vertebrae (NO wedging or Schmorl nodes) (2) Osteochondrodystrophy (earlier in life, extremities show same changes)

Seronegative Spondyloarthritis

= group of joint conditions not associated with rheumatoid factor / rheumatoid nodules

Prevalence:

0.5 1.9%

• 20-fold greater risk to develop spondyloarthritis in patients with positive HLA-B 27 antigen

Subgroups:

• Ankylosing spondylitis 0.86%

• Undifferentiated spondyloarthritis no sacroiliitis 0.67%

• Psoriatic arthritis parasyndesmophytes 0.29%

• Reactive arthritis (eg, Reiter disease)

• Arthropathy of inflammatory bowel disease

Extraaxial involvement:

• uveitis

  calcaneal enthesitis

  peripheral arthritis

Prognosis:	ankylosing spondylitis
Rx:	NSAID, TNF (tumor necrosis factor) inhibitors, intensive physical therapy

Anterior and Posterior Spondylitis

• = Romanus lesion (enthesitis)

• = inflammation of attachment of annulus fibrosus to vertebral endplate (rim of endplate)

  irregularities / erosions involving anterior / posterior edges of vertebral endplates (epiphyseal ring)

  shiny corners = sclerotic changes of edges of vertebral endplates

• MR:

  • hypointense on T1WI + hyperintense on STIR (bone marrow edema / osteitis during acute phase)

  • hyperintense on T1WI (postinflammatory fatty bone marrow degeneration during chronic phase)

Spondylodiskitis

• = Anderson lesion = Rheumatic spondylodiskitis

• = inflammation of intervertebral disk

Prevalence:

8% of patients with ankylosing spondylitis irregularities / erosions of central portion of vertebral endplates

• MR:

• hypointense on T1WI + hyperintense on STIR disk signals involving one / both halves of adjacent vertebral bodies (in acute edematous phase)

Spinal Stenosis

= encroachment on central spinal canal, lateral recess, or neuroforamen by bone / soft tissue

Cause:

• Congenitally short pedicles

  • idiopathic

  • developmental: Down syndrome, achondroplasia, hypochondroplasia, Morquio disease

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• Acquired:

  • Hypertrophy of ligamentum flavum = buckling of ligament secondary to joint slippage in facet joint osteoarthritis (most common)

  • Facet joint hypertrophy

  • Degenerated bulging / herniated disk

  • Spondylosis, spondylolisthesis

  • Surgical fusion

  • Fracture

  • Ossification of posterior longitudinal ligament

  • Paget disease

  • Epidural lipomatosis

Age:	middle-aged for congenital cause / elderly during 6th 8th decade for acquired cause; M > F
Location:	generally involves lumbar spinal canal; cervical spinal canal may be similarly affected obliteration of epidural fat interpedicular distance <25 mm Measurements are not a valid indicator of disease!

Cervical Spinal Stenosis

Location:

multiple levels in mid- and lower cervical spine

• sagittal diameter of cervical spinal canal <13 mm

• hourglass narrowing of thecal sac with scalloping of the dorsal + ventral margins of the cord

• greater degree of stenosis in hyperextended position (due to buckling of ligamenta flava):

  • may appear as spinal block in hyperextended neck on AP views

Lumbar Spinal Stenosis

Cause:

• Achondroplasia:

  • narrowed interpediculate distance progressive toward lumbar spine

• Paget disease: bony overgrowth

• Spondylolisthesis

• Operative posterior spinal fusion

• Herniated disk

• Metastasis to vertebrae

• Developmental / congenital

Age:

presentation between 30 and 50 years of age

• often asymptomatic until middle age (until development of secondary degenerative changes)

• low back pain

• neurogenic / spinal claudication = bilateral lower extremity pain, numbness, weakness worse during walking / standing + relieved in supine position and flexion

• cauda equina syndrome: paraparesis, incontinence, sensory findings in saddlelike pattern, areflexia

  sagittal diameter of spinal canal <16 mm (normal range in adults: 15 23 mm)

  dural sac area <100 mm²

  diminished amount of CSF + crowding of nerve roots

  unusual small quantity of contrast material to fill thecal sac

  anteroposterior + interpediculate diameter spinal canal constricted

  hourglass configuration of thecal sac (SAG view)

  triangular / trefoil shape of thecal sac (AXIAL view)

  redundant serpiginous nerve roots above + below stenosis

  thickened articular process, pedicles, laminae, ligaments

  bulging disks

Split Notochord Syndrome

= spectrum of anomalies with persistent connection between gut + dorsal ectoderm

Etiology:

failure of complete separation of ectoderm from endoderm with subsequent splitting of notochord and mesoderm around the adhesion about 3rd week of gestation
fistula / isolated diverticula / duplication / cyst / fibrous cord / sinus along the tract

Types:

• Dorsal enteric fistula

  • = fistula between intestinal cavity + dorsal midline skin traversing prevertebral soft tissue, vertebral body, spinal canal, posterior elements of spine

  • bowel ostium / exposed pad of mucous membrane in dorsal midline in newborn

  • opening passes meconium + feces

    dorsal bowel hernia into a skin- / membrane-covered dorsal sac after passing through a combined anterior + posterior spina bifida

• Dorsal enteric sinus

  = blind remnant of posterior part of tract with midline opening to dorsal external skin surface

• Dorsal enteric enterogenous cyst

  • = prevertebral / postvertebral / intraspinal enteric-lined cyst derived from intermediate part of tract

  • Intraspinal enteric cyst

    • Age at presentation: 20 40 years

    • intermittent local / radicular pain worsened by elevation of intraspinal pressure

    • Location: intraspinal in lower cervical / upper thoracic region

      enlarged spinal canal at site of cyst

      hemivertebrae, segmentation defect, partial fusion, scoliosis in region of cyst

• Dorsal enteric diverticulum

  = tubular / spherical diverticulum arising from dorsal mesenteric border of bowel as a persistent portion of tract between gut + vertebral column

• Dorsal enteric cyst

  = involution of portion of diverticulum near gut

  mass in abdomen / mediastinum (due to bowel rotation)

Spondylolisthesis

= displacement of one vertebra over another

Direction:	anterolisthesis, retrolisthesis, lateral translation
Prevalence:	4% of general population
Cause:	fracture, infection of anterior column, bone tumor, isthmic spondylolisthesis, scoliosis, degenerative disk disease
Grades I IV (Meyerding method): each grade equals 1/4 anterior subluxation of upper on lower vertebral body

Isthmic Spondylolisthesis = open-arch type

= separation of anterior part (vertebral body, pedicles, transverse processes, superior articular facet) slipping forward from posterior part (inferior facet, laminae, dorsal spinous process)

P.225

Spondylolysis

Cause:	usually bilateral spondylolysis
Age:	often <45 years
Location:	L5-S1 or L4-5
symptomatic if intervertebral disk + posterosuperior aspect of vertebral body encroaches on superior portion of neuroforamen elongation of spinal canal in anteroposterior diameter bilobed configuration of neuroforamen ratio of maximum anteroposterior diameter of spinal canal at any level divided by diameter at L1 >1.25

Degenerative Spondylolisthesis = closed-arch type

• = pseudospondylolisthesis

Cause:	degenerative / inflammatory joint disease (eg, rheumatoid arthritis)
Pathophysiology:	excess motion of facet joints allowing forward / posterior movement
Age:	usually >60 years; M < F (at L4-5)
commonly symptomatic due to spinal stenosis + narrowing of neuroforamen narrowing of spinal canal hypertrophy of facet joints ratio of maximum anteroposterior diameter of spinal canal at any level divided by diameter at L1 <1.25

Spondylolysis

= pars interarticularis defect between superior + inferior articulating processes as the weakest portion of spinal unit

Prevalence:	3 7% of population; in 30 70% other family members afflicted
Age:	early childhood; M:F = 3:1; Whites:Blacks = 3:1

Cause:

• pseudarthrosis following stress (fatigue) fracture of pars (in most) from repetitive minor trauma; common in gymnastics (30%), diving, contact sports (football, soccer, hockey, lacrosse)

• hereditary hypoplasia of pars leads to insufficiency fracture; eg, pars defect in 34% of Eskimos

• secondary spondylolysis: neoplasm, osteomyelitis, Paget disease, osteomalacia, osteogenesis imperfecta

• congenital malformation: frequently associated with spina bifida occulta of S1, dorsally wedge-shaped body of L5, hypoplasia of L5; HOWEVER: no pars defects have been identified in fetal cadavers

symptomatic in 50% (if associated with degenerative disk disease / spondylolisthesis)

Location:

L5 (67 95%); L4 (15 30%); L3 (1 2%); in 75% bilateral

Plain film:

• radiolucent band sclerotic margin resembling the collar of the Scottie dog (on oblique view)

• may be associated with spondylolisthesis

• subluxation of involved vertebra (if pars defect bilateral)

• Wilkinson syndrome = reactive sclerosis + bony hypertrophy of contralateral pedicle + lamina (produced by stress changes related to weakening of neural arch in unilateral pars defect)

Planar / SPECT bone scintigraphy may be useful!

CT:

• pars defect located 10 15 mm above disk space

• inner contour of spinal canal interrupted

Spondylolysis of Cervical Spine

• = progressive degeneration of intervertebral disks leading to proliferative changes of bone + meninges; more common than disk herniation as a cause for cervical radiculopathy

Prevalence:	5 10% at age 20 30; >50% at age 45; >90% by age 60
spastic gait disorder
neck pain
Location:	C4-5, C5-6, C6-7 (greater normal cervical motion at these levels)

Sequelae:

• direct compression of spinal cord

• neural foraminal stenosis

• ischemia due to vascular compromise

• repeated trauma from normal flexion / extension

DDx of myelopathy:

• rheumatoid arthritis, congenital anomalies of craniocervical junction, intradural extramedullary tumor, spine metastases, cervical spinal cord tumor, arteriovenous malformation, amyotrophic lateral sclerosis, multiple sclerosis, neurosyphilis

Syringohydromyelia

• = SYRINGOMYELIA = SYRINX (used in a general manner reflecting difficulty in classification)

• = longitudinally oriented CSF-filled cavities + gliosis within spinal cord frequently involving both parenchyma + central canal

Age:	primarily childhood / early adult life
Cause:	Chiari I malformation (41%), trauma (28%), neoplasm (15%), idiopathic (15%)

• loss of sensation to pain + temperature (interruption of spinothalamic tracts)

• trophic changes [skin lesions; Charcot joints in 25% (shoulder, elbow, wrist)]

• muscle weakness (anterior horn cell involvement)

• spasticity, hyperreflexia (upper motor neuron involvement)

• abnormal plantar reflexes (pyramidal tract involvement)

Location:

predominantly lower end of cervical cord; extension into brainstem (= syringobulbia)

• CT:

  • distinct area of decreased attenuation within spinal cord (100%)

  • swollen / normal-sized / atrophic cord

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  • no contrast enhancement

  • flattened vertebral border (rare) with increased transverse diameter of cord

  • change in shape + size of cord with change in position (rare)

  • filling of syringohydromyelia with intrathecal contrast

  • (a) early filling via direct communication with subarachnoid space

  • (b) late filling after 4 8 hours (80 90%) secondary to permeation of contrast material

• Myelography:

  • enlarged cord (DDx: intramedullary tumor)

  • collapsing cord sign = collapsing of cord with gas myelography as fluid content moves caudad in the erect position (rare)

• MR:

  • cystic area of low signal intensity on T1WI, increased intensity on T2WI

  • presence of CSF flow-void (= low signal on T2WI) within cavity from pulsations

  • beaded cavity from multiple incomplete septations

  • cord enlargement

DDx:

pseudosyrinx = truncation artifact consisting of linear abnormal signal within cord on sagittal images in phase-encoding direction (due to limited number of frequencies for fast Fourier transform)

Hydromyelia

• = PRIMARY / CONGENITAL SYRINGOHYDROMYELIA

• = dilatation of persistent central canal of spinal cord (in 70 80% obliterated), which communicates with 4th ventricle (= communicating syringomyelia)

Histo:

lined by ependymal tissue

• Associated with:

  • Chiari malformation in 20 70% metameric haustrations within syrinx on sagittal T1WI

  • Spinal dysraphism

  • Myelocele

  • Dandy-Walker syndrome

  • Diastematomyelia

  • Scoliosis in 48 87%

  • Klippel-Feil syndrome

  • Spinal segmentation defects

  • Tethered cord (in up to 25%)

DDx:

transient dilatation of the central canal (transient finding in newborns during the first weeks in life)

Syringomyelia

• = ACQUIRED / SECONDARY SYRINGOHYDROMYELIA

• = any cavity within substance of spinal cord that may communicate with the central canal, usually extending over several vertebral segments

Histo:	not lined by ependymal tissue
Pathophysiology:	interrupted flow of CSF through the perivascular spaces of cord between subarachnoid space + central canal

• Cause:

  • Posttraumatic syringomyelia

    Prevalence:	in 3.2% after spinal cord injury
    Location:	68% in thoracic cord 0.5 40 cm (average 6 cm) in length syrinx may be septated (parallel areas of cavitation) on transverse T1WI loss of sharp cord-CSF interface (obliteration of arachnoid space by adhesions) in 44% associated with arachnoid loculations (extramedullary arachnoid cysts) at upper aspect of syrinx

  • Postinflammatory syringomyelia

    subarachnoid hemorrhage, arachnoid adhesions, S/P surgery, infection (tuberculosis, syphilis)

  • Tumor-associated syringomyelia

    spinal cord tumors, herniated disk; secondary to circulatory disturbance + thoracic spinal cord atrophy

  • Vascular insufficiency

Reactive Cyst

• = POSTTRAUMATIC SPINAL CORD CYST

• = CSF-filled cyst adjacent to level of trauma; usually single (75%)

• late deterioration in patients with spinal cord injury (not related to severity of original injury)

• Rx: shunting leads to clinical improvement

Teratoma of spine

= neoplasm containing tissue belonging to all 3 germinal layers at sites where these tissues do not normally occur

Prevalence:	0.15% (excluding sacrococcygeal teratoma)
Age:	all ages; M:F = 1:1
Path:	solid, thin- / thick-walled partially / wholly cystic with clear / milky / dark cyst fluid, uni- / multilocular, presence of bone / cartilage
Location:	intra- / extramedullary complete block at myelography syringomyelia above level of tumor spinal canal may be focally widened

Terminal Myelocystocele

= combination of posterior spina bifida + meningocele + tethered cord + hydromyelia + cystic dilatation of the distal central canal
Cause:	disturbed CSF circulation resulting in dilatation of ventriculus terminalis + disruption of dorsal mesenchyme
Associated with:	anorectal + genitourinary + vertebral anomalies (anal atresia, cloacal exstrophy, scoliosis, sacral agenesis)
skin-covered mass in lumbosacral region spinal cord surrounded dorsally + ventrally by dilated subarachnoid space of the meningocele nerve root exit ventrally bifid spinal cord hydromyelia

Tethered cord

• = TIGHT FILUM TERMINALE SYNDROME = LOW CONUS MEDULLARIS

• = abnormally short + thickened filum terminale with position of conus medullaris below L2-3 (normal location of tip of conus medullaris: L 4/5 at 16 weeks of gestation, L 2/3 at birth, L1-2 >3 months of age)

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RULE OF THREES: above L3 by age 3 months!

Etiology:	incomplete involution of distal spinal cord with failure of ascent of conus
Pathophysiology:	stretching of cord leads to vascular insufficiency at level of conus
Age at presentation:	5 15 years (in years of growth spurt); M:F = 2:3
Associated with:	filar lipoma in 29 78%, filar cyst, diastematomyelia, imperforate anus

• dorsal nevus, dermal sinus tract, hair patch (50%)

• bowel + bladder dysfunction in childhood

• spastic gait with muscle stiffness

• lower extremity weakness + muscle atrophy

• asymmetric hyporeflexia + fasciculations

• orthopedic anomalies: scoliosis, pes cavus, tight Achilles tendon

• hypalgesia, dysesthesia

• paraplegia, paraparesis

• radiculopathy (adults)

• hyperactive deep tendon reflexes

• extensor plantar responses

• anal / perineal pain (in adults)

• back pain (particularly with exertion)

• @ Tight filum

  • diameter of filum terminale >2 mm (normal range of 0.5 to 2 mm) at L5 S1 level (55%)

  • small fibrolipoma within thickened filum (23%)

  • small filar cyst (3%)

  • spinal cord ending in a small lipoma (13%)

• @ Tethered cord (100%)

  • conus medullaris below level of L3 at birth and below L2 by age 12 (86%)

  • abnormal dorsal fixation of cord adjacent to vertebral arches (in prone position)

  • reduced / absent pulsatile movement of the cord + nerve roots (on M-mode scanning)

  • widened triangular thecal sac tented posteriorly (thecal sac pulled posteriorly by filum)

  • abnormal lateral course of nerve roots (>15 angle relative to spinal cord)

• @ Vertebrae

  • lumbar spina bifida occulta with interpedicular widening

  • scoliosis (20%)

MR:

• prolonged T1 relaxation in center of spinal cord on T1WI in 25% (? myelomalacia / mild hydromyelia)

Rx:	decompressive laminectomy / partial removal of lipoma freeing of cord
Dx:	tip of conus medullaris below L2-3

Traumatic Neuroma

= nonneoplastic proliferation of the proximal end of a severed / partially transected injured nerve

Histo:

nonencapsulated tangled multidirectional regenerating axonal masses + Schwann cells + endo- and perineural cells in dense collagenous matrix with surrounding fibroblasts

Types:

• spindle neuroma = internal focal fusiform swelling

  Cause: chronic friction / irritation of nondisrupted injured but intact nerve trunk

• lateral / terminal neuroma

  Cause: severe trauma with partial avulsion / disruption / total transection of nerve

Time of onset:

1 12 months after injury

• pain

• Tinel sign = palpation / tapping on lesion reproduces pain

Location: lower extremity (after amputation), head and neck (after tooth extraction), radial nerve, brachial plexus

fusiform mass / focal enlargement with entering and exiting nerve (spindle type)

bulbous mass in continuity with normal nerve proximally (lateral / terminal type)

MR:

• isointense to muscle on T1WI

• heterogeneous intermediate to high signal intensity on T2WI

• fascicular sign = heterogeneous ringlike pattern on T2WI

Rx:

acupuncture, cortisone injection, transcutaneous / direct nerve stimulation, physical therapy, surgical resection

Ventriculus Terminalis

= small ependyma-lined oval cyst at the transition from the tip of the conus medullaris to the origin of the filum terminale

Origin:	result of canalization and regressive differentiation of the caudal end of the developing spinal cord during embryogenesis
Size:	8 10 mm long, 2 4 mm in diameter Regresses during the first weeks after birth

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Differential Diagnosis of Brain Disorders

Birth trauma

• Caput succedaneum

  • = localized edema in presenting portion of scalp, frequently associated with microscopic hemorrhage + subcutaneous hyperemia

  • Cause: common after vaginal delivery

    • soft superficial pitting edema

      • crosses suture lines

• Subgaleal hemorrhage

  • = hemorrhage between galea aponeurotica (= central fascia formed by occipitofrontal + temporoparietal muscles) and periosteum of outer table

  • may become symptomatic secondary to significant blood loss in children

  • firm fluctuant mass increasing in size after birth

  • may dissect into subcutaneous tissue of neck

  • usually resolves over 2 3 weeks

    • Occasionally due to spontaneous decompression of intracranial (epidural) hematoma

• Cephalohematoma

  • = hematoma beneath outer layer of periosteum

  • Cause: incorrect application of obstetric forceps / skull fracture during birth

  • Incidence: 1 2% of all deliveries

  • Location: most commonly parietal

  • firm tense mass

  • usually increase in size after birth

  • resolution in few weeks to months

  • crescent-shaped lesion adjacent to outer table of skull

  • will not cross cranial suture line

  • may calcify / ossify causing thickening of diploe

• Skull fracture

  • Incidence: 1% of all deliveries

    • CT shows associated intracranial hemorrhage

• Subdural hemorrhage

  • convexity hematoma

  • interhemispheric hematoma

  • posterior fossa hematoma

• Benign subdural effusion

  • =benign condition that resolves spontaneously

  • clear / xanthochromic fluid with elevated protein level

    • extracerebral fluid collection accompanied by ventricular dilatation (= communicating hydrocephalus caused by impaired CSF absorption of these subdural fluid collections)

Increased intracranial pressure

• Intracranial mass

• Hydrocephalus

• Malignant hypertension

• Diffuse cerebral edema

• Increased venous pressure

• Elevated CSF protein

• Pseudotumor cerebri

• papilledema

  • enlargement of perioptic nerve subarachnoid space

Prolactin elevation

Normal level: up to 25 ng/mL

Cause:

• Interference with hypothalamic-pituitary axis:

  • hypothalamic tumor

  • parasellar tumor

  • pituitary adenoma

  • sarcoidosis

  • histiocytosis

  • traumatic infundibular transection

• Pharmacologic agents

  • alpha-methyldopa, reserpine, phenothiazine, butyrophenone, tricyclic antidepressants, oral contraceptives

• Hypothyroidism (TRH also stimulates prolactin)

• Renal failure

• Cirrhosis

• Stress / recent surgery

• Breast examination

• Pregnancy

• Lactation

Stroke

= generic term designating a heterogeneous group of cerebrovascular disorders

Incidence:

• 3rd leading cause of death in United States (after heart disease + cancer); 2nd leading cause of death due to cardiovascular disease in U.S.; 2nd leading cause of death in patients >75 years of age; 450,000 new cases per year; 160 new strokes per 100,000 population per year; leading cause of death in Orient

Age: >55 years (12% occur in young adults); M:F = 2:1

Risk factors: heredity, hypertension (50%), smoking, diabetes (15%), obesity, familial hypercholesterolemia, myocardial infarction, atrial fibrillation, congestive heart failure, alcoholic excess, substance abuse, oral contraceptives, pregnancy, high anxiety + stress

Etiology:

• NONVASCULAR (5%): eg, tumor, hypoxia

• VASCULAR (95%)

  • Brain infarction = ischemic stroke (80%)

    • Occlusive atheromatous disease of extracranial (35%) / intracranial (10%) arteries = large vessel disease between aorta + penetrating arterioles

      • critical stenosis, thrombosis,

      • plaque hemorrhage / ulceration / embolism

    • Small vessel disease of penetrating arteries (25%) = lacunar infarct

    • Cardiogenic emboli (6 15 23%)

      • Ischemic heart disease with mural thrombus

        • acute myocardial infarction (3% risk/year)

        • cardiac arrhythmia

      • Valvular heart disease

        • postinflammatory (rheumatic) valvulitis

        • infective endocarditis (20% risk/year)

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        • nonbacterial thrombotic endocarditis (30% risk/year)

        • mitral valve prolapse (low risk)

        • mitral stenosis (20% risk/year)

        • prosthetic valves (1 4% risk/year)

      • Nonvalvular atrial fibrillation (6% risk/year)

      • Left atrial myxoma (27 55% risk/year)

    • Nonatheromatous disease (5%)

      • elongation, coil, kinks (up to 20%)

      • fibromuscular dysplasia (typically spares origin + proximal segment of ICA)

      • aneurysm (rare) may occur in cervical / petrous portion / intracranially

      • dissection: traumatic / spontaneous (2%); up to 15% of strokes in young adults

      • cerebral arteritis (Takayasu, collagen disease, lymphoid granulomatosis, temporal arteritis, Beh et disease, chronic meningitis, syphilis)

      • postendarterectomy thrombosis / embolism / restenosis

    • Overactive coagulation (5%)

  • Hemorrhagic stroke (20%)

    • Primary intracerebral hemorrhage (15%)

      • Hypertensive hemorrhage (40 60%)

      • Amyloid angiopathy (15 25%)

      • Vascular malformation (10 15%)

      • Drugs: eg, anticoagulants (1 2%)

      • Bleeding diathesis (<1%): eg, hemophilia

    • Vasospasm due to nontraumatic SAH (4%)

      • Ruptured aneurysm (75 80%)

      • Vascular malformation (10 15%)

      • Nonaneurysmal SAH (5 15%)

    • Veno-occlusive disease (1%): sinus thrombosis

• May be preceded by TIA:

  • 10 14% of all strokes are preceded by TIA!

  • 60% of all strokes ascribed to carotid disease are preceded by TIA!

Prognosis:

• death during hospitalization (25%): alteration in consciousness, gaze preference, dense hemiplegia have a 40% mortality rate

• survival with varying degrees of neurologic deficit (75%)

• good functional recovery (40%)

  • Hypodensity involving >50% of MCA territory has a fatal outcome in 85%!

Clinical diagnosis inaccurate in 13%!

Role of imaging:

• Confirm clinical diagnosis

• Identify primary intracerebral hemorrhage

• Detect structural lesions mimicking stroke:

  • tumor, vascular malformation, subdural hematoma

• Detect early complications of stroke:

  • cerebral herniation, hemorrhagic transformation

Indications for cerebrovascular testing:

• TIA = transient ischemic attack

• Progression of carotid disease to 95 98% stenosis

• Cardiogenic cerebral emboli

Temporal classification:

• TIA = transient ischemic attack

  • lasts 5 to 30 minutes

• RIND = reversible ischemic neurologic deficit

  • = fully reversible prolonged ischemic event resulting in minor neurologic dysfunction

  • >24 hours and <8 weeks

  • Incidence: 16 per 100,000 population per year

• Progressing stroke / intermittent progressive stroke = stepwise / gradually progressing accumulative neurologic deficit evolving over hours / days

• Slow stroke = rare clinical syndrome presenting as developing neuronal fatigue with weakness in lower / proximal upper extremity after exercise; occurs in patients with occluded internal carotid artery

• Completed stroke = severe + persistent stable neurologic deficit = cerebral infarction (death of neuronal tissue) as end stage of prolonged ischemia >21 days

  • level of consciousness correlates well with size of infarction

Prognosis: 6 11% recurrent stroke rate

Transient ischemic attack

= brief episode of transient focal neurological deficit owing to ischemia of <24 hours duration with return to pre-attack status

Incidence: 31 per 100,000 population per year; increasing with age up to 300; 105,000 new cases per year in United States; M > F

Cause:

• embolic: usually from ulcerative plaque at carotid bifurcation

• hemodynamic: fall in perfusion pressure distal to a high-grade stenosis / occlusion

Risk factors:

• Hypertension (linear increase in probability of stroke with increase in diastolic blood pressure)

• Cardiac disorders (prior myocardial infarction, angina pectoris, valvular heart disease, dysrhythmia, congestive heart failure)

• Diabetes mellitus

• Cigarette smoking (weak)

Prognosis: 5.3% stroke rate per year for 5 years after first TIA; per year 12% increase of stroke / myocardial infarction / death; complete stroke in 33% within 5 years; complete stroke in 5% in 1 month

Carotid Transitory Ischemic Attack (2/3)

• carotid attacks <6 hours in 90%

• transient weakness / sensory dysfunction CLASSICALLY in

  • hand / face with embolic event

  • proximal arm + lower extremity with hemodynamic event (watershed area)

• motor dysfunction = weakness, paralysis, clumsiness of one / both limbs on same side

• sensory alteration = numbness, loss of sensation, paresthesia of one / both limbs on same side

• speech / language disturbance = difficulty in speaking (dys- / aphasia) / writing, in comprehension of language / reading / performing calculations

• visual disturbance = loss of vision in one eye, homonymous hemianopia, amaurosis fugax

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  • paresis (mono-, hemiparesis) in 61%

  • paresthesia (mono-, hemiparesthesia) in 57%

  • amaurosis fugax (= transient premonitory attack of impaired vision due to retinal ischemia) in 12% caused by transient hypotension or emboli of platelets / cholesterol crystals, which may be revealed by funduscopy

  • facial paresthesia in 30%

Vertebrobasilar Transient Ischemic Attack (1/3)

• vertebrobasilar events <2 hours in 90%

• motor dysfunction = as with carotid TIA but sometimes changing from side to side including quadriplegia, diplopia, dysarthria, dysphagia

• sensory alteration = as with carotid TIA usually involving one / both sides of face / mouth / tongue

• visual loss = as with carotid TIA including uni- / bilateral homonymous hemianopia

• disequilibrium of gait / postural disturbance, ataxia, imbalance / unsteadiness

• drop attack = sudden fall to the ground without loss of consciousness

• binocular visual disturbance in 57%

• vertigo in 50%

• paresthesia in 40%

• diplopia in 38%

• ataxia in 33%

• paresis in 33%

• headaches in 25%

• seizures in 1.5%

Accelerating / crescendo TIA

= repeated periodic events of neurologic dysfunction with complete recovery to normal in interphase

Rx:

• Carotid endarterectomy (1% mortality, 5% stroke)

• Anticoagulation

• Antiplatelet agent: aspirin, ticlopidine (Ticlid )

  • in patients with recently symptomatic TIA /minor stroke + >70% carotid artery stenosis: prophylactic carotid endarterectomy + chronic low-dose aspirin therapy

Dementia

• Alzheimer disease

• Pick disease

• Normal pressure hydrocephalus

• Subdural hematoma

• rain mass

Trigeminal Neuropathy

• facial pain, numbness, weakness of masticatory muscles, trismus

• diminished / absent corneal reflex

• abnormal jaw reflex

• decreased pain / touch / temperature sensation

• atrophy of masticatory muscles

• tic douloureux = paroxysmal facial pain (usually confined to V₂ and V₃) mainly caused by neurovascular compression (tortuous elongated superior cerebellar artery / anterior inferior cerebellar artery / vertebrobasilar dolichoectasia / venous compression)

• BRAINSTEM LESION

  • Vascular: infarct, AVM

  • Neoplastic: glioma, metastasis

  • Inflammatory: multiple sclerosis (1 8%), herpes rhombencephalitis

  • Other: syringobulbia

• CISTERNAL CAUSES

  • Vascular: aneurysm, AVM, vascular compression

  • Neoplastic: acoustic schwannoma, meningioma, trigeminal schwannoma, epidermoid cyst, lipoma, metastasis

  • Inflammatory: neuritis

• MECKEL CAVE + CAVERNOUS SINUS

  • Vascular: carotid aneurysm

  • Neoplastic: meningioma, trigeminal schwannoma, epidermoid cyst, lipoma, pituitary adenoma, base of skull neoplasm, metastasis, perineural tumor spread

  • Inflammatory: Tolosa-Hunt syndrome

• EXTRACRANIAL

  • Neoplastic: neurogenic tumor, squamous cell carcinoma, adenocarcinoma, lymphoma, adenoid cystic carcinoma, mucoepidermoid carcinoma, melanoma, metastasis, perineural tumor spread

  • Inflammatory: sinusitis

  • Other: masticator space abscess, trauma

Classification of CNS anomalies

• DORSAL INDUCTION ANOMALY

  • = defects of neural tube closure

  • Anencephaly

  • Cephalocele at 4 weeks

  • Chiari malformation at 4 weeks

  • Spinal dysraphism

  • Hydromyelia

• VENTRAL INDUCTION ANOMALY

  • = defects in formation of brain vesicles + face

  • Holoprosencephaly: 5 6 weeks

  • Septo-optic dysplasia: 6 7 weeks

  • Dandy-Walker malformation: 7 10 weeks

  • Agenesis of septum pellucidum

• NEURONAL PROLIFERATION & HISTOGENESIS

  • Neurofibromatosis: 5 weeks 6 months

  • Tuberous sclerosis: 5 weeks 6 months

  • Primary hydranencephaly: >3 months

  • Neoplasia

  • Vascular malformation (vein of Galen, AVM, hemangioma)

• NEURONAL MIGRATION ANOMALY

  • due to infection, ischemia, metabolic disorders

  • Schizencephaly: 2 months

  • Agyria + pachygyria: 3 months

  • Gray matter heterotopia: 5 months

  • Dysgenesis of corpus callosum: 2 5 months

  • Lissencephaly

  • Polymicrogyria

  • Unilateral megalencephaly

• DESTRUCTIVE LESIONS

  • Hydranencephaly

  • Porencephaly

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  • Hypoxia: periventricular leukomalacia, germinal matrix hemorrhage

  • Toxicosis

  • Infections (TORCH)

    • Toxoplasmosis

    • Other: syphilis, hepatitis, zoster

    • Rubella

      • punctate / nodular calcifications

      • porencephalic cysts

      • occasionally microcephaly

    • Cytomegalovirus inclusion disease

      • typically punctate / stippled / curvilinear

      • periventricular calcifications

      • often hydrocephalus

    • Herpes simplex

Absence of Septum Pellucidum

• Holoprosencephaly

• Callosal agenesis

• Septo-optic dysplasia

• Schizencephaly

• Severe chronic hydrocephalus

• Destructive porencephaly

Phakomatoses

• [phako, Greek = lens / lentil-shaped object]

• = neurocutaneous SYNDROMES = NEUROECTODERMAL DYSPLASIAS

• = development of benign tumors / malformations in organs of ectodermal origin (CNS, eye, skin)

• autosomal dominant:

  • Neurofibromatosis (von Recklinghausen)

  • Tuberous sclerosis (Bourneville)

  • Retinocerebellar hemangioblastoma (von Hippel-Lindau)

  • Neurocutaneous melanosis

• not autosomal dominant:

  • Encephalotrigeminal angiomatosis (Sturge-Weber-Dimitri)

  • Ataxia-telangiectasia

Degenerative diseases of cerebral hemispheres

= progressive fatal disease characterized by destruction / alteration of gray and white matter

Etiology: genetic; viral infection; nutritional disorders (eg, anorexia nervosa, Cushing syndrome); immune system disorders (eg, AIDS); exposure to toxins (eg, CO); exposure to drugs (eg, alcohol, methotrexate + radiation)

Leukodystrophy

• = degenerative diffuse sclerosis with symmetrical bilateral white matter lesions

Leukoencephalopathy

• = disease of white matter

Myelinoclastic / Demyelinating Disease

• = disease that destroys normally formed myelin

• Usually affects older children / adults

• infectious

  • Progressive multifocal leukoencephalopathy

  • Subacute sclerosing panencephalitis (SSPE)

  • Acute disseminated encephalomyelitis (ADEM)

• noninfectious

  • Radiation

  • Anoxia

  • Hypertensive encephalopathy

  • Disseminated necrotizing leukoencephalopathy (from methotrexate therapy)

• others

  • Multiple sclerosis (most frequent primary demyelinating disease)

  • Alzheimer disease (most common of diffuse gray matter degenerative diseases)

  • Parkinson disease (most common subcortical degenerative disease)

  • Creutzfeldt-Jakob disease

  • Menkes disease (sex-linked recessive disorder of copper metabolism)

  • Globoid cell leukodystrophy

  • Spongiform degeneration

  • Cockayne syndrome

  • Spongiform leukoencephalopathy

  • Myelinoclastic diffuse sclerosis (Schilder disease)

Dysmyelinating Disease

• = metabolic disorder (= enzyme deficiency) resulting in deficient / absent myelin sheaths

• Usually presents in first 2 years / 1st decade of life!

• Associated with white matter atrophy

• macrencephalic:

  • Alexander disease (frontal areas affected first)

  • Canavan disease (white matter diffusely affected)

• hyperdense thalami, caudate nuclei, corona radiata

  • Krabbe disease

• family history (X-linked recessive)

  • X-linked adrenoleukodystrophy

  • Pelizaeus-Merzbacher disease

• others

  • Metachromatic leukodystrophy (most common hereditary leukodystrophy)

  • Binswanger disease (SAE)

  • Multi-infarct dementia (MID)

  • Pick disease

  • Huntington disease

  • Wilson disease

  • Reye syndrome

  • Mineralizing microangiopathy

  • Diffuse sclerosis

Vascular disease of brain

Classification of Vascular CNS Anomalies

• VASCULAR MALFORMATION

  • arterial = arteriovenous malformation (AVM)

    • Facial / brain arteriovenous malformation

    • Vein of Galen malformation

  • capillary = capillary telangiectasia

    • Capillary angioma

    • Facial port wine stain

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  • venous = venous malformation

    • Venous angioma

    • Sinus pericranii

  • lymphatic

    • Cystic hygroma

  • combinations

    • Sturge-Weber disease

    • Rendu-Osler-Weber disease

• VASCULAR TUMOR

  • Hemangioma

    • capillary hemangioma: seen in children, involution by 7 years of age in 95%

    • cavernous hemangioma: seen in adults, no involution

  • Hemangiopericytoma

  • Hemangioendothelioma

  • Angiosarcoma

Occlusive Vascular Disease

• Embolic state:

  • single vascular territory

• Hypoperfusive state:

  • multiple vascular territories

Cause:

• Vasospasm from subarachnoid hemorrhage

• Embolic infarction (50%)

  • thrombus (atrial fibrillation, valvular disease, Atheromatous plaques of extracerebral arteries, fibromuscular dysplasia, intracranial aneurysm, surgery, paradoxic emboli, sickle cell disease, atherosclerosis, thrombotic thrombocytopenic purpura)

    • fluctuating blood pressures

    • hypercoagulability

      • cerebral petechial hemorrhage within cortical / basal gray matter during 2nd week (from fragments of embolus) in up to 40%; initial ischemia is followed by reperfusion (= HALLMARK of embolic infarction)

      • supernormal artery on NECT = high-density material lodged in cerebral vessel near major bifurcations

      • atheromatous narrowing of vessels

  • fat

  • nitrogen

• Watershed infarct

  • involving deep white matter between two adjacent vascular beds in global hypoperfusion secondary to poor cardiac output / cervical carotid artery occlusion 6% of cerebral infarcts have hemorrhage (red infarct)

  • stroke (3rd most common cause of death in USA, 5% of stroke syndromes are caused by underlying tumor)

  • TIA = transitory ischemic attack: clears within 24 hrs

  • RIND = reversible ischemic neurologic deficit: still evident >24 hours with eventual total recovery

  • amaurosis fugax = transient monocular blindness

  • weakness / numbness in an extremity

  • aphasia

  • dizziness, diplopia, dysarthria (vertebrobasilar ischemia)

• Hypertension

  • Hypertensive encephalopathy

    • diffuse white matter hypodensity (edema secondary to arterial spasm)

  • Hypertensive hemorrhage

    • Location: basal ganglia (putamen, external capsule), thalamus, pons, cerebellum

  • Lacunar infarction

  • Subcortical arteriosclerotic encephalopathy

• Amyloidosis

  • involvement of small- + medium-sized arteries of meninges + cortex

  • normotensive patient >65 years of age

  • multiple simultaneous / recurrent cortical hemorrhages

• Vasculitis

  • Bacterial meningitis, TB, syphilis, fungus, virus, rickettsia

  • Collagen-vascular disease: Wegener granulomatosis, polyarteritis nodosa, SLE, scleroderma, dermatomyositis

  • Granulomatous angitis: giant cell arteritis, sarcoidosis, Takayasu disease, temporal arteritis

  • Inflammatory arteritis: rheumatoid arteritis, hypersensitivity arteritis, Beh et disease, lymphomatoid granulomatosis

  • Drug-induced: IV amphetamine, ergot preparations, oral contraceptives

  • Radiation arteritis = mineralizing microangiopathy

  • Moyamoya disease

• Anoxic encephalopathy

  • cardiorespiratory arrest, near-drowning, drug overdose, CO poisoning

• Venous thrombosis

Multiple Infarctions

• Typical in extracranial occlusive disease, cardiac output problems, small vessel disease; in 6% from a shower of emboli

Location: usually bilateral + supratentorial (3/4); supra- and infratentorial (1/4)

Brain atrophy

Cerebral Atrophy

= irreversible loss of brain substance + subsequent enlargement of intra- and extracerebral CSF-containing spaces (hydrocephalus ex vacuo = ventriculomegaly)

• DIFFUSE BRAIN ATROPHY

  • Cause:

    • Trauma, radiation therapy

    • Drugs (dilantin, steroids, methotrexate, marijuana, hard drugs, chemotherapy), alcoholism, hypoxia

    • Demyelinating disease (multiple sclerosis, encephalitis)

    • Degenerative disease

      • eg, Alzheimer disease, Pick disease, Jakob-Creutzfeldt disease

    • Cerebrovascular disease + multiple infarcts

    • Advancing age, anorexia, renal failure enlarged ventricles + sulci

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• FOCAL BRAIN ATROPHY

  • Cause: vascular / chemical / metabolic / traumatic / idiopathic (Dyke-Davidoff-Mason syndrome)

• REVERSIBLE PROCESS SIMULATING ATROPHY

  • (in younger people)

  • Cause: anorexia nervosa, alcoholism, catabolic steroid treatment, pediatric malignancy

  • prominent sulci

  • ipsilateral dilatation of basal cisterns + ventricles

  • ex vacuo dilatation of ventricles

  • thinning of gyri

Cerebellar Atrophy

• WITH CEREBRAL ATROPHY

  • = generalized senile brain atrophy

• WITHOUT CEREBRAL ATROPHY

  • Olivopontocerebellar degeneration / Marie ataxia / Friedreich ataxia

    • onset of ataxia in young adulthood

  • Ataxia-telangiectasia

  • Ethanol toxicity: predominantly affecting midline (vermis)

  • Phenytoin toxicity: predominantly affecting cerebellar hemispheres

  • Idiopathic degeneration secondary to carcinoma (= paraneoplastic), usually oat cell carcinoma of lung

  • Radiotherapy

  • Focal cerebellar atrophy:

    • infarction

    • traumatic injury

Hippocampal Atrophy

• Alzheimer disease

• Mesial temporal sclerosis

  • complex partial seizures

• Normal in octogenarians

Brain herniation

= shift of normal brain to another site due to mass effect by tumor, trauma or infection

Transtentorial Herniation

• descending = downward toward the posterior fossa

  • oculomotor paresis (cranial n. III):

    • ipsilateral dilated pupil

      • due to unopposed sympathetic activity while parasympathetic fibers traveling on outside of CNN III are compressed by uncus

    • abnormal EOMs

  • contralateral hemiparesis

    • due to compression of ipsilateral cerebral peduncles above decussation of corticospinal tracts

  • ipsilateral hemiparesis (false localizer)

    • due to severe lateral translation of brainstem across perimesencephalic cistern pushing contralateral CNN III + peduncles against opposite tentorial edge

    • widening of ipsilateral ambient cistern

    • widening of ipsilateral prepontine cistern

    • widening of contralateral temporal horn

    • Cx:

      • Occipital infarction (from compression of ipsilateral posterior cerebral artery against cerebral peduncle by uncus + parahippocampal gyrus

      • Durette hemorhage = dorsolateral brainstem / pons hemorrhage from stretching of pontine perforators by downward displacement of pons

      • Kernohan notch = hemorrhage in central midbrain due to compression of contralateral cerebral peduncle against incisura

    • anterior / uncal transtentorial herniation (most common) caused by lesion in anterior half of brain

      • uncus displaced into suprasellar cistern

      • truncation of six-pointed star appearance of suprasellar cistern

    • posterior: herniation of parahippocampal gyrus

    • total: herniation of entire hippocampus

• ascending = upward (superior vermian): displacement of cerebellum through tentorial incisura

  • Cause: slowly growing cerebellar / brainstem process

  • nausea & vomiting obtundation coma

    • spinning top appearance of midbrain due to bilateral compression on posterolateral aspect of midbrain

    • narrowing of ambient cistern

    • narrowing of quadrigeminal plate cistern

    • Cx: hydrocephalus

Subfalcine Herniation

• = contralateral shift of midline structures under falx cerebri

• May be associated with: transtentorial herniation

• headache contralateral leg weakness

  • amputation of ispilateral frontal horn

  • widened CSF space at contralateral anterior falx

  • degree of shift measured in mm between straight line formed by posterior falx + location of septum pellucidum on axial image

  • shift of cingulate gyrus under falx

• Cx: ipsilateral distal anterior cerebral infarction

Alar / Retroalar / Sphenoid Herniation

= herniation of frontal lobe posteriorly across edge of sphenoid ridge

Associated with: transtentorial + subfalcine herniation

• paucity of clinical symptomatology, clinically occult

• posterior: frontal lobe mass

• anterior: temporal lobe / insula lesion

•  MCA displacement

Transforaminal Herniation

= herniation of inferior mesial portions of cerebellum downward through foramen magnum (= inferior tonsillar)

• cerebellar tonsils at level of dens on axial images

• cerebellar tonsils 5 mm below foramen magnum in adults, 7 mm in children on sagittal / coronal images

Cx: obtundation death

Displacement of vessels

• ARTERIAL SHIFT

  • Pericallosal arteries

    • Round shift = frontal lesion anterior to coronal suture

    P.235

    
    

    • Square shift = lesion behind foramen of Monro in lower half of hemisphere

      

      Sylvian Triangle and Intracranial Shifts

    • Distal shift = posterior to coronal suture in upper half of hemisphere

    • Proximal shift = basifrontal lesion / anterior middle cranial fossa including anterior temporal lobe

  • Sylvian triangle

    • = branches of MCA within sylvian fissure on outer surface of insula form a loop upon reaching the upper margin of the insula; serves as angiographic landmark for localizing supratentorial masses

  • Location of lesion:

    • anterior sylvian frontal region

    • suprasylvian posterior frontal + parietal

    • retrosylvian occipital, parieto-occipital

    • infrasylvian temporal lobe + extracerebral region

    • intrasylvian usually due to meningioma

    • lateral sylvian frontal, frontotemporal, parietotemporal

    • central sylvian deep posterior frontal, basal ganglia

• CEREBRAL VEINS

  • = indicate the midline of the posterior part of the forebrain showing the exact location of the roof of the 3rd ventricle

Hypodense brain lesions

Diffusely Swollen Hemispheres

• METABOLIC

  • Metabolic encephalopathy: eg, uremia, Reye syndrome, ketoacidosis

  • Anoxia: cardiopulmonary arrest, near-drowning, smoke inhalation, ARDS

• NEUROVASCULAR

  • Hypertensive encephalopathy

  • Superior sagittal sinus thrombosis

  • Head trauma

  • Pseudotumor cerebri

• INFLAMMATION

  • eg, herpes encephalitis, CMV, toxoplasmosis

Brain Edema

= increase in brain volume due to increased tissue-water content (80% for gray matter + 68% for white matter is normal)

Etiology:

• Cytotoxic edema

  • reversible increase in intracellular water content secondary to ischemia / anoxia (axonal pallor) which leads to depletion of ATP with ion pump dysfunction of cell membrane and an increase in intracellular Na⁺ and K⁺

  P.236

  
  

  • characteristically seen in cerebral infarction

  • 30 60 min after onset of symptoms

    • positive diffusion weighted imaging

• Vasogenic edema (most common form)

  • passage of water from capillaries into extracellular space due to damage of capillary endothelium; increase in pinocytotic activity with passage of protein across vessel wall into intercellular space (lack of contrast enhancement means breakdown of blood-brain barrier is not the cause)

  • associated with primary brain neoplasm, metastases, hemorrhage, inflammation, infarction

  • takes >3 6 hours; requires residual / reestablished blood flow

  • DDx: blood-brain barrier break-down after 8 10 days

Types:

• Hydrostatic edema

  • rapid increase / decrease in intracranial pressure

• Interstitial edema

  • increase in periventricular interstitial spaces secondary to transependymal flow of CSF with elevated intraventricular pressure

• Hypoosmotic edema

  • produced by overhydration from IV fluid / inappropriate secretion of antidiuretic hormone

• Congestive brain swelling

  • rapid accumulation of extravascular water as a result of head trauma; may become irreversible (brain death) if intracranial pressure equals systolic blood pressure

• decreased distinction between gray + white matter

• compressed slitlike lateral ventricles

• compression of cerebral sulci + perimesencephalic cisterns

CT:

• areas of hypodensity

  • Edema is always greatest in white matter!

• mass effect: flattening of gyri, displacement + deformation of ventricles, midline shift

• return to normal from nonhemorrhagic edema / brain atrophy from white matter shearing injury

MR:

• decreased intensity on T1WI

• increased intensity on T2WI

• enhancement with gadolinium

US:

• generalized / focal increase of parenchymal echogenicity with featureless appearance

• decreased resistive indices

Midline Cyst

• Cavum septi pellucidi = 5th ventricle

  • = thin triangular membrane consisting of two glial layers covered laterally with ependyma separating the frontal horns of lateral ventricles

  • Incidence: in 80% of term infants; in 15% of adults

  • Location: posterior to genu of corpus callosum, inferior to body of corpus callosum, anterosuperior to anterior pillar of fornix

  • extends to foramen of Monro

  • may dilate + cause obstructive hydrocephalus (rare)

• Cavum vergae = 6th ventricle

  • = cavity posterior to columns of fornix; contracts after about 6th gestational month

  • Incidence: in 30% of term infants; in 15% of adults

  • Location: posterior to fornix, anterior to splenium of corpus callosum, inferior to body of corpus callosum, superior to transverse fornix

  • posterior midline continuation of cavum septi pellucidi beyond foramen of Monro

• Cavum veli interpositi

  • = extension of quadrigeminal plate cistern above 3rd ventricle to foramen of Monro, laterally bounded by columns of fornix + thalamus

• Colloid cyst:

  • anterior + superior to cavum septi pellucidi

• Arachnoid cyst:

  • in region of quadrigeminal plate cistern

  • curvilinear margins

Cyst with Mural Nodule

• Pilocytic astrocytoma (childhood)

• Ganglioglioma

• Pleomorphic xanthoastrocytoma

• Glioblastoma multiforme

• Hemangioblastoma (posterior fossa, spinal cord)

Multiple Tiny CNS Cysts

• DIFFUSE DEGENERATIVE DISEASE

• DIFFUSE INFLAMMATORY PROCESS

• LOW-GRADE CYSTIC NEOPLASM

  • Ganglioglioma

  • Pyelocytic astrocytoma

  • Pleomorphic xanthoastrocytoma

Cholesterol-containing CNS Lesions

• Epidermoid inclusion cyst

• Cholesterol granuloma

• Acquired epidermoid of middle ear

• Congenital cholesteatoma of middle ear

• Craniopharyngioma

Mesencephalic Low-density Lesion

• Normal: decussation of superior cerebellar peduncles at level of inferior colliculi

• Syringobulbia

  • found in conjunction with syringomyelia, Arnold-Chiari malformation, trauma

    • CSF density centrally

    • intrathecal contrast enters central cavity

• Brainstem infarction

  • abnormal contrast enhancement after 1 week

  • well-defined low-attenuation region without enhancement after 2 4 weeks

• Central pontine myelinolysis

• Brainstem glioma

  • mass with indistinct margins + vague enhancement

• Metastasis

  • well-defined contrast enhancement

• Granuloma in TB / sarcoidosis (rare)

P.237

Intracranial Pneumocephalus

• TRAUMA (74%):

  • blunt trauma

    • in 3% of all skull fractures; in 8% of fractures involving paranasal sinuses (frontal > ethmoid > sphenoid > mastoid) or base of skull

  • penetrating injury

• NEOPLASM INVADING SINUS (13%):

  • Osteoma of frontal / ethmoid sinus

  • Pituitary adenoma

  • Mucocele, epidermoid

  • Malignancy of paranasal sinuses

• INFECTION WITH GAS-FORMING ORGANISM (9%)

  • in mastoiditis, sinusitis

• SURGERY (4%):

  • hypophysectomy, paranasal sinus surgery

Mechanism of dural laceration:

• ball-valve mechanism during straining, coughing, sneezing

• vacuum phenomenon secondary to loss of CSF

Time of onset: on initial presentation (25%), usually seen within 4 5 days, delay up to 6 months (33%)

Mortality: 15%

Cx:

• CSF rhinorrhea (50%)

• Meningitis / epidural / brain abscess (25%)

• Extracranial pneumocephalus

  • = air collection in subaponeurotic space

Hyperdense intracranial lesions

Intracranial Calcifications

mnemonic: PINEEAL

• Physiologic

• Infection

• Neoplasm

• Endocrine

• Embryologic

• Arteriovenous

• Leftover Ls

• PHYSIOLOGIC INTRACRANIAL CALCIFICATIONS

• INFECTION

  • TORCH (toxoplasmosis, others [syphilis, hepatitis, zoster], CMV, rubella, herpes), healed abscess, hydatid cyst, granuloma (tuberculoma, actinomycosis, coccidioidomycosis, cryptococcosis, mucormycosis), cysticercosis, trichinosis, paragonimiasis

  • mnemonic:

    • CMV calcifications are circumventricular

    • Toxoplasma calcifications are intraparenchymal

• NEOPLASM

  • Craniopharyngioma (40 80%), oligodendroglioma (50 70%), chordoma (25 40%), choroid plexus papilloma (10%), meningioma (20%), pituitary adenoma (3 5%), pinealoma (10 20%), dermoid (20%), lipoma of corpus callosum, ependymoma (50%), astrocytoma (15%), after radiotherapy, metastases (1 2%, lung > breast > GI tract)

  • N.B.: Astrocytomas calcify less frequently but are the most common tumor!

• ENDOCRINE

  • Hyperparathyroidism, hypervitaminosis D, hypoparathyroidism, pseudohypoparathyroidism, CO poisoning, lead poisoning

• EMBRYOLOGIC

  • Neurocutaneous syndromes (tuberous sclerosis, Sturge-Weber, neurofibromatosis), Fahr disease, Cockayne syndrome, basal cell nevus syndrome

• ARTERIOVENOUS

  • Atherosclerosis, aneurysm, AVM, occult vascular malformation, hemangioma, subdural + epidural hematomas, intracerebral hemorrhage

• LEFTOVER Ls

  • Lipoma, lipoid proteinosis, lissencephaly

Physiologic Intracranial Calcification

• Pineal calcification

  • Age: no calcification <5 years of age, in 8 10% at 8 14 years of age, in 40% by 20 years of age, 2/3 of adult population

  • amorphous / ringlike calcification <3 mm from midline usually <10 mm in diameter

  • approximately 30 mm above highest posterior elevation of pyramids

  • CAVE: pineal calcification >14 mm suggests pineal neoplasm (teratoma / pinealoma)

• Habenula

  • Incidence: approximately in 1/3 of population

  • Age: >10 years of age

  • posteriorly open C-shaped calcification 4 6 mm anterior to pineal gland

• Choroid plexus

  • may calcify in all ventricles: most commonly in glomus within atrium of lateral ventricles, near foramen of Monro, tela choroidea of 3rd ventricle, roof of 4th ventricle, along foramina of Luschka

  • Age: >3 years of age

  • 20 30 mm behind + slightly below pineal on lateral projection, symmetrical on AP projection

  • DDx: neurofibromatosis

• Dura, falx cerebri, falx cerebelli, tentorium

  • Incidence: 10% of population

  • Age: >3 years of age

  • DDx: basal cell nevus syndrome (Gorlin syndrome), pseudoxanthoma elasticum, congenital myotonic dystrophy

• Petroclinoid ligament (= reflection of tentorium) between tip of dorsum sellae and apex of petrous bone

  • Age: >5 years of age

• Interclinoid ligament

  • = interclinoid bridging

• Arteriosclerosis: particularly intracavernous segment of ICA, basilar a., vertebral a.

• Basal ganglia

Increased Density of Falx

• Subarachnoid hemorrhage

• Interhemispheric subdural hematoma

• Diffuse cerebral edema (= increased density relative to low-density brain)

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• Dural calcifications (hypercalcemia from chronic renal failure, basal cell nevus syndrome, hyperparathyroidism)

• Normal falx (can be normal in pediatric population)

Intraparenchymal Hemorrhage

mnemonic: ITHACANS

• Infarction (hemorrhagic)

• Trauma

• Hypertensive hemorrhage

• Arteriovenous malformation

• Coagulopathy

• Aneurysm, Amyloid angiopathy

• Neoplasm: metastasis / primary neoplasm

• Sinus thrombosis

Dense Cerebral Mass

Substrate: calcification / hemorrhage / dense protein

• VESSEL

  • Aneurysm

  • Arteriovenous malformation

  • Hematoma (acute / subacute)

• TUMOR

  • Lymphoma

  • Medulloblastoma

  • Meningioma

  • Metastasis

    • from mucinous-producing adenocarcinoma

    • hemorrhagic metastases: melanoma, choriocarcinoma, hypernephroma, bronchogenic carcinoma, breast carcinoma (rarely)

Brain masses

Classification of Primary CNS Tumors

Incidence: 9% of all primary neoplasms (5th most common primary neoplasm); 5 10 cases per 100,000 population per year; account for 1.2% of autopsied deaths

• TUMORS OF BRAIN AND MENINGES

  • Gliomas

    • Astrocytoma (50%)

      • Astrocytoma (astrocytoma grades I II)

      • Glioblastoma (astrocytoma grades III IV)

    • Oligodendroglioma

    • Paraglioma

      • Ependymoma

      • Choroid plexus papilloma

      

      Intracranial Tumors in Adult Population

      Incidence of Brain Tumors

      All Age Groups		Pediatric Age Group
      Glioma	34%	Astrocytoma	50%
      Meningioma	17%	Medulloblastoma	15%
      Metastasis	12%	Ependymoma	10%
      Pituitary adenoma	6%	Craniopharyngioma	6%
      Neurinoma	4%	Choroid plexus papilloma	2%
      Sarcoma	3%
      Granuloma	3%
      Craniopharyngioma	2%
      Hemangioblastoma	2%

    • Ganglioglioma

    • Medulloblastoma

  • Pineal tumor

    • Germinoma

    • Teratoma

    • Pineocytoma

    • Pineoblastoma

  • Pituitary tumor

    • Pituitary adenoma

    • Pituitary carcinoma

  • Meningioma

  • Nerve sheath tumor

    • Schwannoma

    • Neurofibroma

  • Miscellaneous

    • Sarcoma

    • Lipoma

    • Hemangioblastoma

• TUMORS OF EMBRYONAL REMNANTS

  • Craniopharyngioma

  • Colloid cyst

  • Teratoid tumor

    • Epidermoid

    • Dermoid

    • Teratoma

CNS Tumors Presenting at Birth

• Hypothalamic astrocytoma

• Choroid plexus papilloma / carcinoma

• Teratoma

• Primitive neuroectodermal tumor

• Medulloblastoma

• Ependymoma

• Craniopharyngioma

CNS Tumors in Pediatric Age Group

Incidence:

2.4:100,000 (<15 years of age); 2nd most common pediatric tumor (after leukemia); 15% of all pediatric neoplasms; 15 20% of all primary brain tumors; M > F

• increased intracranial pressure

• increasing head size

• SUPRATENTORIAL (50%)

  • Age: first 2 3 years of life

  • Covering of brain: dural sarcoma, schwannoma, meningioma (3%)

  P.239

  
  

  • Cerebral

    Differences of Some Pediatric CNS Tumors

    	PNET	Ependymoma	Astrocytoma
    CT	hyper	iso	hypo
    T2WI	intermed.	intermed.	increased
    Enhancement	moderate	minimal	nodule
    Calcification	10 15%	40 50%	<10%
    Cyst formation	rare	common	typical
    CSF seeding	15 40%	rare	rare
    Foraminal spread	no	yes	no

  • hemisphere: astrocytoma (37%), oligodendroglioma

  • Corpus callosum: astrocytoma

  • 3rd ventricle: colloid cyst, ependymoma

  • Lateral ventricle: ependymoma (5%), choroid plexus papilloma (12%)

  • Optic chiasm: craniopharyngioma (12%), optic nerve glioma (13%), teratoma, pituitary adenoma

  • Hypothalamus: glioma (8%), hamartoma

  • Pineal region: germinoma, pinealoma, teratoma (8%)

• INFRATENTORIAL (50%)

  • Age: 4 11 years

  • Cerebellum: astrocytoma (31 33%), PNET / medulloblastoma (26 31%)

  • Brainstem: glioma (16 21%)

  • 4th ventricle: ependymoma (6 14%), choroid plexus papilloma

  • mnemonic: BE MACHO

  • Brainstem glioma

  • Ependymoma

  • Medulloblastoma

  • AVM

  • Cystic astrocytoma

  • Hemangioblastoma

  • Other

Supratentorial Tumor with Mural Nodule

• Extraventricular ependymoma

• Pleomorphic xanthoastrocytoma

• Hemispheric pilocytic astrocytoma

• Ganglioglioma

• Dysembryoplastic neuroepithelial tumor (DNET)

Supratentorial Midline Tumors

• Optic + hypothalamic glioma (39%)

• Craniopharyngioma (20%)

• Astrocytoma (9%)

• Pineoblastoma (9%)

• Germinoma (6%)

• Lipoma (6%)

• Teratoma (3.5%)

• Pituitary adenoma (3.5%)

• Meningioma (2%)

• Choroid plexus papilloma (2%)

Differences between Meningioma and Schwannoma

	Meningioma	Schwannoma
Angle with dura	obtuse	acute
Dural tail	frequent	rare
Calcification	20%	rare
Cystic/necrotic	rare	10%
IAC involvement	rare	80%
NECT	hyperdense	isodense
Enhancement	uniform	32% nonuniform

Classification by Histology

• Astrocytic tumors (33.5%)

• Primitive neuroectodermal tumor = PNET (21%) highly malignant neoplasms originating from germinal matrix + containing glial + neural elements

  • Medulloblastoma (16%)

  • Ependymoblastoma (2.5%)

  • PNET of cerebral hemisphere (2.5%)

• Mixed gliomas (16%)

• Malformative tumors (11.5%)

  • Craniopharyngioma (5.5%)

  • Lipoma (4.5%)

  • Dermoid cyst (1%)

  • Epidermal cyst (0.5%)

• Choroid plexus tumors (4%)

• Ependymal tumors (4%)

• Tumors of meningeal tissues (3.5%)

  • Meningioma (3%)

  • Meningeal sarcoma (0.5%)

• Germ cell tumors (2.5%)

  • Germinoma (1.5%)

  • Teratomatous tumor (1%)

• Neuronal tumors

  • Gangliocytoma (1.5%)

• Tumors of neuroendocrine origin

  • Pituitary adenoma (1%)

• Oligodendroglial tumors (0.5%)

• Tumors of blood vessel

  • Hemangioma (1%)

Superficial Gliomas

= peripherally located cortical neoplasms serving as a seizure focus

• Ganglioglioma

• Desmoplastic infantile ganglioglioma

• Gangliocytoma

  Posterior Fossa Tumor In Adult

  Extraaxial	Intraaxial
  1. Acoustic neuroma	1. Metastasis (lung, breast)
  2. Meningioma	2. Hemangioblastoma
  3. Chordoma	3. Lymphoma
  4. Choroid plexus papilloma	4. Lipoma
  5. Epidermoid	5. Glioma

P.240




• Dysplastic cerebellar gangliocytoma

• Pleomorphic xanthoastrocytoma

• Dysembryoplastic neuroepithelial tumor

Multifocal CNS Tumors

• METASTASES FROM PRIMARY CNS TUMOR

  • via commissural pathways: corpus callosum, internal capsule, massa intermedia

  • via CSF: ventricles / subarachnoid cisterns

  • satellite metastases

• MULTICENTRIC CNS TUMOR

  • true multicentric gliomas (4%)

  • concurrent tumors of different histology (coincidental)

• MULTICENTRIC MENINGIOMAS (3%) without neurofibromatosis

• MULTICENTRIC PRIMARY CNS LYMPHOMA

• PHAKOMATOSES

  • Generalized neurofibromatosis:

    • meningiomatosis, bilateral acoustic neuromas, bilateral optic nerve gliomas, cerebral gliomas, choroid plexus papillomas, multiple spine tumors, AVMs

  • Tuberous sclerosis:

    • subependymal tubers, intraventricular gliomas (giant cell astrocytoma), ependymomas

  • von Hippel-Lindau disease:

    • retinal angiomatosis, hemangioblastomas, congenital cysts of pancreas + liver, benign renal tumors, cardiac rhabdomyomas

Multifocal Deep Hemispheric Masses

• Primary CNS Lymphoma

• Gliomatosis cerebri

  • nonenhancing tumor extension (common)

CNS Tumors Metastasizing Outside CNS

mnemonic: MEGO

• Medulloblastoma

• Ependymoma

• Glioblastoma multiforme

• Oligodendroglioma

Large Heterogeneous Intracerebral Mass

• High-grade glioma

  • increased relative cerebral blood volume (rCBV) in zone of edema on perfusion-weighted images

• Metastasis

  • reduced relative cerebral blood volume (rCBV) in zone of edema on perfusion-weighted images

Mass with Large Tumor Vessels and Edema

• Glioblastoma multiforme

• Meningioma

Avascular Mass of Brain

mnemonic: TEACH

• Tumor: astrocytoma, metastasis, oligodendroglioma

• Edema

• Abscess

• Cyst, Contusion

• Hematoma, Herpes

Calcified Intracranial Mass

• Oligodendroglioma (frequent, but rare tumor)

• Low-grade astrocytoma (in 10 20%)

mnemonic: Ca²⁺ COME

• Craniopharyngioma

• Astrocytoma, Aneurysm

• Choroid plexus papilloma

• Oligodendroglioma

• Meningioma

• Ependymoma

Enhancing brain lesions

Solitary Ring-enhancing Lesion of Brain

• NEOPLASM

  • Primary neoplasm: high-grade glioma, meningioma, lymphoma, leukemia, pituitary macroadenoma, acoustic neuroma, craniopharyngioma

  • Metastatic carcinoma + sarcoma

• INFECTION / INFLAMMATION

  • 1. Abscess: bacterial, fungal, parasitic

  • 3. Empyema of epidural / subdural / intraventricular spaces

• HEMORRHAGIC-ISCHEMIC LESION

  • Resolving infarction

  • Aging hematoma

  • Operative bed following resection

  • Thrombosed aneurysm

• DEMYELINATING DISORDER

  • Radiation necrosis

  • Tumefactive demyelinating lesion ( singular sclerosis )

  • Necrotizing leukoencephalopathy after methotrexate

Pathogenesis:

• hypervascular margin of lesion = granulation tissue / peripheral vascular channels / hypervascular tumor capsule

• breakdown of blood-brain barrier = leakage of contrast out of abnormally permeable vessels into extracellular fluid space

• hypodense center = avascular / hypovascular (requires time to fill) / cystic degeneration

Incidence of ring blush:

• abscess (in 73%); glioblastoma (in 48%); metastasis (in 33%); grade II astrocytoma (in 26%) [NOT in grade I astrocytoma]

mnemonic: MAGICAL DR

• Metastasis

• Abscess / cerebritis

• Glioblastoma multiforme, Glioma

• Infarct (resolving), Impact

• Contusion

• AIDS toxoplasmosis

• Lymphoma (often AIDS-related)

• Demyelinating disease

• Radiation necrosis, Resolving hematoma

P.241

Small Spherical Ring-enhancing Lesion at Corticomedullary Margin & Substantial Amount of Vasogenic Edema

• Metastasis

• Abscess of brain

  • bacterial, fungal, granulomatous

  • parasitic: cysticercosis, paragonimiasis, echinococcus

• Subacute infarction

• Resolving hematoma

Well-defined Superficial Enhancing Mass

• Extraaxial dura-based tumor

  • displacement of underlying cortex

  • adjacent dural thickening

  • reactive bone changes

  • supply by dural arteries

  • Meningioma

  • Metastasis (prostate, breast, melanoma, RCC)

  • Lymphoma

• Intraaxial

  • Glioblastoma multiforme

Dense & Enhancing Lesions

• Aneurysm

• Meningioma

• CNS lymphoma

• Medulloblastoma

• Metastasis

Multifocal Enhancing Lesions

• Multiple infarctions

• Arteriovenous malformations

• Multifocal primary / secondary neoplasms

• Multifocal infectious processes

• Demyelinating disease: eg, multiple sclerosis

Innumerable Small Enhancing Cerebral Nodules

• METASTASES

• PRIMARY CNS LYMPHOMA

• DISSEMINATED INFECTION

  • Cysticercosis

  • Histoplasmosis

  • Tuberculosis

• INFLAMMATION

  • Sarcoidosis

  • Multiple sclerosis

• SUBACUTE MULTIFOCAL INFARCTION

  • from hypoperfusion, multiple emboli, cerebral vasculitis (SLE), meningitis, cortical vein thrombosis

Enhancing Lesion in Internal Auditory Canal

• NEOPLASTIC

  • Acoustic schwannoma

  • Ossifying hemangioma

• NONNEOPLASTIC

  • Sarcoidosis

  • Meningitis

  • Postmeningitic / postcraniotomy fibrosis

  • Vascular loop of anterior inferior cerebellar a.

Brain ventricles

Ventriculomegaly

• MACROCEPHALY

  • increased intraventricular pressure

  • Obstruction to CSF flow

    • Communicating hydrocephalus

    • Noncommunicating hydrocephalus

  • Overproduction of CSF

    • = nonobstructive hydrocephalus

  • Neoplasm

• MICROCEPHALY

  • normal intraventricular pressure

  • Primary failure of brain growth

    • dysgenesis

      • Holoprosencephaly

      • Aneuploidy syndromes (trisomies)

      • Migrational (<6 layers)

    • environment: alcohol, drugs, toxins

    • infection: TORCH

  • Loss of brain mantle

    • Infection: TORCH

    • Vascular accident:

      • Hydranencephaly

      • Schizencephaly

      • Porencephaly

    • Hemorrhage:

      • Porencephaly

      • Leukomalacia

• normocephaly

Colpocephaly

= dilatation of trigones + occipital horns + posterior temporal horns of lateral ventricles

• Agenesis of corpus callosum

• Arnold-Chiari malformation

• Holoprosencephaly

Enhancing Ventricular Margins

• Subependymal spread of metastatic tumor

  • Bronchogenic carcinoma (esp. small cell ca.)

  • Melanoma

  • Breast carcinoma

• Subependymal seeding of CNS primary

  • Glioma

  • Ependymoma

  • Giant cell astrocytoma

• Ependymal seeding of CNS primary

  • Medulloblastoma

  • Germinoma

• Primary CNS lymphoma / systemic lymphoma

• Inflammatory ventriculitis

Intraventricular Tumor

Prevalence: 10% of all intracranial neoplasms

• Ependymoma 20%

• Astrocytoma 18%

• Colloid cyst 12%

• Meningioma 11%

• Choroid plexus papilloma 7%

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• Epidermoid / dermoid 6%

• Craniopharyngioma 6%

• Medulloblastoma 5%

• Cysticercosis 5%

• Arachnoid cyst 4%

• Subependymoma 2%

• AVM 2%

• Teratoma 1%

• Metastasis

• Intraventricular neurocytoma

• Oligodendroglioma

Supratentorial Intraventricular Tumors

• Lateral ventricle (3/4)

  • Choroid plexus tumor (44%)

  • Giant cell astrocytoma in tuberous sclerosis (19%)

  • Hemangioma in Sturge-Weber syndrome (12%)

• Third ventricle (1/4)

  • Astrocytoma (13%)

  • Choroid plexus tumor (6%)

  • Meningioma (6%)

Uniformly Enhancing Tumor in Trigone of Lateral Ventricle

• Choroid plexus papilloma

• Ependymoma

• Vascular malformation

• Meningioma

Dense Lesion near Foramen of Monro

• INTRAVENTRICULAR LESION

  • Colloid cyst

  • Meningioma

  • Choroid plexus tumor / granuloma

  • AVM of septal, thalamostriate, internal cerebral veins

• PERIVENTRICULAR MASS

  • Primary CNS lymphoma

  • Tuberous sclerosis

    • subependymal tuber

    • giant cell astrocytoma

  • Metastasis from mucin-producing adenocarcinoma / hemorrhagic metastasis (melanoma, choriocarcinoma, hypernephroma, bronchogenic carcinoma, breast carcinoma)

  • Glioblastoma of septum pellucidum

• MASSES PROJECTING SUPERIORLY FROM SKULL BASE

  • Pituitary adenoma

  • Craniopharyngioma

  • Aneurysm

  • Dolichoectatic basilar artery

Tumor in 3rd Ventricle

• Colloid cyst

• Glioma

• Aneurysm

• Craniopharyngioma

• Ependymoma

• Meningioma

• Choroid plexus papilloma

• Intraventricular neurocytoma

Tumor in 4th Ventricle

• Choroid plexus papilloma

• Ependymoma / glioma

• Hemangioblastoma

• Vermian metastasis

• AVM

• Epidermoid tumor (rare)

• Inflammatory mass

• Cyst

Periventricular region

Periventricular Calcifications in Childhood

• Tuberous sclerosis

• Congenital infection: CMV, toxoplasmosis

Periventricular Hypodensity

• Encephalomalacia

  • slightly denser than CSF

• Porencephaly

  • = cavity communicating with ventricle / cistern from intracerebral hemorrhage

  • Associated with: dilated ventricle, sulci, and fissures CSF density

• Resolving hematoma

  • history of previously demonstrated hematoma

  • may show ring enhancement + compression of adjacent structures

• Cystic tumor

  • mass effect + contrast enhancement

Periventricular T2-hyperintense Lesions

• NORMAL

  • Enlarged perivascular spaces

    • = small invaginations of subarachnoid space following pia mater along perforating nutrient end vessels into brain substance

    • Location: inferior third of putamen = tat cribl (cribriform / sievelike); usually bilateral

    • 1 2-mm round lesions isointense to CSF (well seen on coronal sections through centrum semiovale + on low-axial sections at level of anterior commissure)

  • Ependymitis granularis

    • =symmetric focal areas of hyperintensity on T2WI in normal individuals

    • Location: anterior + lateral to frontal horns

    • punctate / up to 1 cm in diameter

    • grossly triangular in shape

    • Histo: patchy loss of ependyma with paucity of hydrophobic myelin (astrocytic gliosis), which allows migration of fluid out of the ventricle into interstitium

• DEMYELINATING DISEASE

  • Multiple sclerosis

  • Acute disseminated encephalomyelitis (ADEM)

  • Multifocal leukoencephalopathy

  • Lymphomatoid granulomatosis

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• VASCULAR DISEASE

  • Arteriolosclerosis / small vessel disease

    • = microangiopathy = Arteriolosclerosis

    • = deep white matter ischemia

    • = extensive number of perivascular fluid spaces predominantly at arteriolar level as part of subacute arteriosclerotic encephalopathy

      • Cause: chronic ischemia due to arteriosclerosis of long penetrating arteries arising from circle of Willis (lenticulostriate + thalamo-perforators)

      • Predisposed: cigarette smoker, chronic hypertension, diabetes mellitus, cerebral amyloid angiopathy

      • Histo: lipohyalin deposits within vessel walls followed by partial demyelination, gliosis, interstitial edema

      • Incidence: in 2 10% without risk factors, in 84% with risk factors and symptoms

      • Age: >60 years (in 30 60%); >65 years almost universal; M:F = 1:1

      • Location: periventricular white matter > optic radiation > basal ganglia > centrum semiovale > brainstem (usually spares corpus callosum + subcortical U-fibers)

      • multiple focal lesions <2 mm

      • small randomly located lesions throughout deep + subcortical white matter, basal ganglia

    • ultiple lacunar infarcts

    • Migraine: in 41% with classic migraine, in 57% with complicated migraine; presumed to represent vasculitis-induced small infarcts

    • Vasculitis:

      • Primary angitis of CNS (PACNS), polyarteritis nodosa, Wegener granulomatosis, SLE, Beh et disease, syphilis, Sj gren syndrome, sickle cell

    • Sarcoidosis

    • Antiphospholipid antibodies (non-SLE)

    • Susac syndrome

  • INFECTION / INFLAMMATION

    • HIV encephalitis:

      • well-defined patchy / ill-defined dirty white matter

      • central atrophy

    • Lyme encephalopathy

    • Neurocysticercosis

    • Fungal disease

  • TUMOR

    • Subependymal tumor

    • Multiple parenchymal metastases

    • Intravascular (angiocentric) lymphoma

  • TRAUMA

    • Diffuse axonal / shearing injury

    • Diffuse white matter injury

      • = radiation-induced demyelination of periventricular white matter

      • Cause: whole-brain irradiation

      • subclinical

  • Diffuse necrotizing leukoencephalopathy

    • Cause: intrathecal methotrexate whole brain irradiation

    • rapidly deteriorating clinical course

    • confluent pattern with scalloped margins within periventricular white matter extending out to subcortical U-fibers

• METABOLIC

  • Vitamin B₁₂ deficiency

  • Hydrocephalus = transependymal CSF flow

    • smooth halo of even thickness

  • Pseudotumor cerebri

• GENETIC

  • Neurofibromatosis 1

  • Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)

  • Fabry disease

Multifocal Black Dots on T2 + T2* GRE

= chronic microbleeds, blooming on T2* GRE

• Cerebral amyloid disease

• Hypertensive microhemorrhages

• Hemorrhagic lacunar infarcts

• Multiple vascular malformations (capillary telangiectasia, cavernous malformation)

• Traumatic diffuse axonal injury

• Hemorrhagic metastases

• Metallic microemboli from artificial heart valves

• CADASIL

Basal ganglia

Bilateral Basal Ganglia Lesions in Childhood

• Basal ganglia are susceptible to damage during childhood because of high energy requirements (ATP) mandating a rich blood supply + high concentration of trace metals (iron, copper, manganese)

• increased irritability, lethargy, dystonia

• seizure, behavioral changes

• bilateral necrosis of basal ganglia

Acute Basal Ganglia Lesions in Childhood

• Compromise of vascular supply

  • Hemolytic-uremic syndrome

    • causing microthrombosis of basal ganglia, thalami, hippocampi, cortex

  • Encephalitis (usually viral agents)

• Compromise of nutrient supply

  • Hypoxia: respiratory arrest, near drowning, strangling, barbiturate intoxication

  • Hypoglycemia

    • hemorrhage rarely seen

  • Osmotic myelinolysis

    • associated central pontine location common

• Acute poisoning

  • Carbon monoxide

    • preferentially affects globus pallidus rare in children:

    • Hydrogen sulfide

    • Cyanide poisoning

    P.244

    
    

    • Methanol poisoning

Chronic Basal Ganglia Lesions in Childhood

• Inborn errors of metabolism

  • Leigh disease

    • = subacute necrotizing encephalomyelopathy

    • = autosomal recessive disorder characterized by deficiencies in pyruvate carboxylase, pyruvate dehydrogenase complex, cytochrome c oxidase resulting in anaerobic ATP production

    • lactic acidosis (elevated ratio of lactate to pyruvate in CSF + serum)

    • propensity to involve putamen

  • Wilson disease

    • = hepatolenticular degeneration

    • = increased deposition of copper in brain + liver

    • decreased levels of serum copper + ceruloplasmin

    • increased urinary copper excretion

    • cell damage of lenticular nucleus (= lenslike configuration of putamen + globus pallidus)

  • Mitochondrial encephalomyelopathies

    • = subset of lactic acidemias with structurally abnormal mitochondria

    • ragged red fibers in muscle biopsy

  • Maple syrup urine disease

    • = inability to catabolize branched-chain amino acids (leucine, isoleucine, valine)

    • urine smells of maple syrup

  • Methylmalonic acidemia

    • = group of genetically distinct autosomal recessive disorders of organic acid metabolism affecting conversion of methylmalonyl-CoA to succinyl-CoA

    • accumulation of methylmalonic acid in blood + urine

• Degenerative disease

  • Huntington disease

  • Dystrophic calcifications

• Dysmyelinating disease

  • basal ganglia are a mixture of gray + white matter

    • Canavan disease

    • Metachromatic leukodystrophy

  • Others

    • Neurofibromatosis type 1

Low-attenuation Lesion in Basal Ganglia

• Poisoning: carbon monoxide, barbiturate intoxication, hydrogen sulfide poisoning, cyanide poisoning, methanol intoxication

• Hypoxia

• Hypoglycemia

• Hypotension (lacunar infarcts)

• Wilson disease

Basal Ganglia Calcification

Prevalence in children: 1.1 1.6%

• PHYSIOLOGIC WITH AGING

• ENDOCRINE

  • Hypoparathyroidism, pseudo~, pseudopseudo~ (60%)

  • Hyperparathyroidism

  • Hypothyroidism

• METABOLIC

  • Leigh disease

  • Mitochondrial cytopathy

    • Kearns-Sayre syndrome = ophthalmoplegia, retinal pigmentary degeneration, complete heart block, short stature, mental deterioration

    • MELAS = Mitochondrial myopathy, Encephalopathy, Lactic acidosis, And Stroke

    • MERRF = Myoclonic Epilepsy with Ragged Red Fibers

  • Fahr disease = familial cerebrovascular ferrocalcinosis

• CONGENITAL / DEVELOPMENTAL

  • Familial idiopathic symmetric basal ganglia calcification

  • Hastings-James syndrome

  • Cockayne syndrome

  • Lipoid proteinosis = hyalinosis cutis

  • Neurofibromatosis

  • Tuberous sclerosis

  • Oculocraniosomatic disease

  • Methemoglobinopathy

  • Down syndrome

• INFLAMMATION / INFECTION

  • Toxoplasmosis, congenital rubella, CMV

  • Measles, chicken pox

  • Pertussis, Coxsackie B virus

  • Cysticercosis

  • Systemic lupus erythematosus

  • AIDS

• TRAUMA

  • Childhood leukemia following methotrexate therapy

  • S/P radiation therapy

  • Birth anoxia, hypoxia

  • Cardiovascular event

• TOXIC

  • Carbon monoxide poisoning

  • Lead intoxication

  • Nephrotic syndrome

mnemonic: BIRTH

• Birth anoxia

• Idiopathic (most common), Infarct

• Radiation therapy

• Toxoplasmosis / CMV

• Hypoparathyroidism / pseudoHPT

Multiple Small Enhancing Lesions in Deep Nuclei

• Metastases

• Primary CNS lymphoma

• Disseminated infection

• Noninfectious inflammatory process

• Subacute mutlifocal infarction

• Vasculitis

Linear Echogenic Foci in Thalamus + Basal Ganglia

• IN UTERO INFECTION

  • = mineralizing vasculopathy = destruction of wall of lenticulostriate arteries + replacement by deposits of amorphous granular basophilic material

  • TORCH agents: Toxoplasma, others (syphilis, hepatitis, zoster), rubella virus, cytomegalovirus, herpes virus

  P.245

  
  

  • Syphilis

  • Human immunodeficiency virus

• CHROMOSOMAL ABNORMALITY

  • Down syndrome

  • Trisomy 13

• OTHERS (anoxic injury?)

  • Perinatal asphyxia, respiratory distress syndrome, cyanotic congenital heart disease, necrotizing enterocolitis

  • Fetal alcohol syndrome

  • Nonimmune hydrops

Eye-of-the-Tiger Sign

= markedly hypointense globus pallidus on T2WI surrounding a higher-intensity center

Cause: excess iron accumulation + central gliosis

Associated with: Hallervorden-Spatz syndrome (Hallervorden-Spatz disease, dementia, tetraparesis, neurofibrillary tangles, retinitis pigmentosa, acanthocytosis, pallidal degeneration, X-linked disorders with mental retardation + Dandy-Walker malformation, disorders with Lewy bodies); extrapyramidal parkinsonian disorders

No Caption Available.

Meninges

Diffuse Dural Thickening

• Metastasis:

  • prostate, melanoma, breast, rectum, lymphoma

• Meningioma

• Granuloma: TB, sarcoid, syphilis

• Wegener granulomatosis

• Granulomatous angitis

• Erdheim-Chester disease (lipid granulomatosis)

• Rheumatoid arthritis

• Neuroblastoma

• Idiopathic hypertrophic pachymeningitis

• Pachymeningitis interna hemorrhagica (breast mets)

Dural Tail Sign

= curvilinear area of enhancement tapering off from the margin of the lesion along dural surface (due to dural tumor infiltration / reactive inflammatory hypervascularity)

• Meningioma

• Acoustic schwannoma

  • Other superficial masses

• Chloroma

• Primary CNS lymphoma

• Sarcoidosis

• Syphilitic gumma

• Metastasis

Leptomeningeal Disease

• INFLAMMATION

  • Langerhans cell histiocytosis

  • Sarcoidosis

  • Wegener granulomatosis

  • Chemical meningitis: rupture of epidermoid

• INFECTION

  • Bacterial meningitis

  • Tuberculous meningitis

  • Fungal meningitis

  • Neurosyphilis

• TUMOR

  • Primary meningeal tumor

    • Meningioma

    • Glioma: primary leptomeningeal glioblastomatosis / gliosarcomatosis

    • Melanoma / melanocytoma

    • Sarcoma

    • Lymphoma

  • CSF-spread from primary CNS tumor

    • Medulloblastoma

    • Germinoma

    • Pineoblastoma

  • Metastasis

    • Breast carcinoma

    • Lymphoma / leukemia

    • Lung carcinoma

    • Malignant melanoma

    • Gastrointestinal carcinoma

    • Genitourinary carcinoma

• TRAUMA

  • Old subarachnoid hemorrhage

  • Surgical scarring from craniotomy

  • Lumbar puncture

Gyral Enhancement

• MENINGEAL TUMOR

  • Meningeal carcinomatosis from systemic tumor, eg, breast carcinoma, small cell carcinoma of lung, malignant melanoma, lymphoma / leukemia

  • Seeding primary CNS tumor:

    • Medulloblastoma

    • Pineoblastoma

    • Ependymoma

  • MENINGITIS

    • pyogenic, tuberculous, fungal, cysticercosis, sarcoidosis

  • VASCULAR

    • Subarachnoid hemorrhage

      • (enhancing fibroblastic proliferation)

    • Subacute / acute brain infarct: luxury perfusion

    • Dural sinus thrombosis: venous congestion

  mnemonic: CAL MICE

  • Cerebritis

  • Arteriovenous malformation

  • Lymphoma

  • Meningitis

  • Infarct

  • Carcinomatosis

  • Encephalitis

Extraaxial lesions

Extraaxial Tumor

mnemonic: MABEL

• Meningioma

• Arachnoid cyst

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• Bony lesion

• Epidermoid

• Leukemic / lymphomatous infiltration

Low-attenuation Extraaxial Lesion

• Acoustic schwannoma (occasionally low-density mass)

• Epidermoid tumor

• Arachnoid cyst

Pericerebral Fluid Collection in Childhood

• ENLARGED SUBARACHNOID SPACE

  • due to macrocephaly

  • due to brain atrophy

    • superficial cortical veins cross subarachnoid space to reach superior sagittal sinus

    • wide sulci, normal configuration of gyri

    • normal / prominent size of ventricles

• SUBDURAL FLUID COLLECTION

  • Subdural hygroma

  • Subdural empyema / abscess (due to meningitis)

  • Subdural hematoma

    • superficial cortical veins are prevented from crossing the subarachnoid space by the presence of arachnoid / neomembrane

    • wide interhemispheric fissure

Subdural Fluid Collection

• Hyperdense = acute subdural hematoma

• Isodense = subacute subdural hematoma

• Hypodense

  • Chronic subdural hematoma

  • Subdural hygroma

  • Effusion from meningo-encephalitis

Jugular Foramen Mass

• NONNEOPLASTIC ENTITIES

  • Asymmetrically enlarged jugular foramen

  • High-riding jugular bulb

  • Dehiscent jugular bulb

    • pulsatile tinnitus

    • vascular tympanic membrane

    • middle ear soft-tissue mass contiguous with jugular foramen (= jugular bulb bulging into middle ear cavity)

      Intra-versus Extraaxial Mass

      	Intraaxial	Extraaxial
      Relationship to dura	no attachment until advanced	contiguous
      Local bony changes	uncommon	common
      Cortex displaced	toward bone	away from bone, buckling of gray + white matter, displacement of vessels
      Subarachnoid cistern	effaced	widened, CSF cleft
      Feeding arteries	pial	dural

    • absence of bony plate separating jugular bulb from posteroinferior middle ear cavity

    • DDx: Jugular megabulb (rises above floor of EAC but with preservation of bony plate)

  • Jugular vein thrombosis

• NEOPLASM

  • Paraganglioma = glomus tumor

  • Nerve sheath tumor = neuroma

  • Meningioma

  • Vascular metastasis (renal / thyroid cancer)

• PRIMARY BONE LESION

  • Multiple myeloma

  • Lymphoma

  • Langerhans cell histiocytosis

Dumbbell Mass Spanning Petrous Apex

• Large trigeminal schwannoma

• Meningioma

• Epidermoid cyst

Cerebellopontine Angle Tumor

= extraaxial tumor arising in CSF-filled space bound by pons + cerebellar hemisphere + petrous bone

Incidence: 5 10% of all intracranial tumors

• cranial neuropathy: high frequency hearing loss (n. VIII), tinnitus + facial motor dysfunction (n. V II), facial sensory dysfunction (n. V), taste disturbance (chorda tympani)

• signs of posterior fossa mass effect: headache, nausea, vomiting, disequilibrium, ataxia

• hemifacial spasm, trigeminal neuralgia (tic douloureux)

  • may widen CSF space (cistern) in 25%

  • bone erosion / hyperostosis

  • sharp margination with brain

Types:

• Acoustic neuroma = schwannoma (80 90%):

  • from intracanalicular portion of 8th cranial nerve

• Meningioma (10 18%)

  • 2nd most common extraaxial mass in posterior fossa; <5% of all intracranial meningiomas; larger + more hemispheric in shape + more homogeneously enhancing than acoustic neuroma

• Epidermoid inclusion cyst (5 9%)

• Arachnoid cyst (<1%)

• Aneurysm of basilar / vertebral / posterior inferior cerebellar artery:

  • congenital berry aneurysm / saccular aneurysm / atherosclerotic dolichoectasia

• Choroid plexus papilloma

• Ependymoma

  Differences between Epidermoid and Arachnoid Cyst

  	Epidermoid	Arachnoid Cyst
  CT density	hyperdense to CSF	CSF-like
  Margins	scalloped	smooth
  Vessels	encased	displaced
  Proton density	deviates from CSF	CSF-like
  Diffusion	restricted	CSF-like

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• Trigeminal neuroma

  • from gasserian ganglion within Meckel cave in the most anteromedial portion of petrous pyramid / trigeminal nerve root

  • Glomus jugulare tumor

    • within adventitia of bulb of jugular vein at base of petrous bone with invasion of posterior fossa

  • Chordoma

  • Exophytic brainstem glioma

    • Histo: usually diffuse fibrillary astrocytoma

  • Metastasis (0.2 2%)

  • Lipoma (<1%)

  mnemonic: Ever Grave CerebelloPontine Angle Masses

  • Epidermoid

  • Glomus jugulare tumor

  • Chondroma, Chordoma, Cholesteatoma

  • Pituitary tumor, Pontine glioma (exophytic)

  • Acoustic + trigeminal neuroma, Aneurysm of basilar / vertebral artery, Arachnoid cyst

  • Meningioma, Metastasis

Corpus Callosum Lesion

• TUMOR

  • GBM

  • Lymphoma

  • Metastasis

• TRAUMA

  • Shearing injury

• WHITE MATTER DISEASE

  • Multiple sclerosis

  • Progressive multifocal leukoencephalopathy

  • Adrenoleukodystrophy

  • Marchiafava-Bignami disease

• INFECTION

  • Toxoplasmosis

Ring-enhancing Lesion Crossing Corpus Callosum

mnemonic: GAL

• Glioblastoma multiforme (butterfly glioma)

• Astrocytoma

• Lymphoma

Posterior fossa

Posterior Fossa Cystic Malformation

• Dandy-Walker malformation

• Dandy-Walker variant

• Megacisterna magna

• Arachnoid pouch

Cystic Mass in Cerebellar Hemisphere

• Hemangioblastoma

• Cerebellar astrocytoma

• Metastasis

• Lateral medulloblastoma (= cerebellar sarcoma )

• Choroid plexus papilloma with lateral extension

Sella

Destruction of Sella

• Pituitary adenoma

• Suprasellar tumor

• Carcinoma of sphenoid + posterior ethmoid sinus

  • opacification of sinus + destruction of walls

  • associated with nasopharyngeal mass (common)

• Nasopharyngeal carcinoma

  • squamous cell carcinoma

  • lymphoepithelioma = Schmincke tumor = non-keratinizing form of squamous cell carcinoma

    • sclerosis of adjacent bone

• Metastasis to sphenoid

  • from breast, kidney, thyroid, colon, prostate, lung, esophagus

• Primary tumor of sphenoid bone (rare)

  • osteogenic sarcoma, giant cell tumor, plasmacytoma

• Chordoma

• Mucocele of sphenoid sinus (uncommon)

• Enlarged 3rd ventricle

  • aqueductal stenosis from infratentorial mass, maldevelopment

J-shaped Sella

mnemonic: CONMAN

• Chronic hydrocephalus

• Optic glioma, Osteogenesis imperfecta

• Neurofibromatosis

• Mucopolysaccharidosis

• Achondroplasia

• Normal variant

Enlarged Sella

• PRIMARY TUMOR

  • Pituitary adenoma

  • Craniopharyngioma

  • Meningioma: hyperostosis

  • Optic glioma: J-shaped sella

• PITUITARY HYPERPLASIA

  • Hypothyroidism

  • Hypogonadism

  • Nelson syndrome (occurring in 7% of patients subsequent to adrenalectomy)

• CSF SPACE

  • Enlarged 3rd ventricle

  • Hydrocephalus

  • Empty sella

• VESSEL

  • Arterial aneurysm

  • Ectatic internal carotid artery

mnemonic: CHAMPS

• Craniopharyngioma

• Hydrocephalus (empty sella)

• AVM, Aneurysm

• Meningioma

• Pituitary adenoma

• Sarcoidosis, TB

Pituitary Gland Enlargement

• Neoplasm: eg, pituitary gland adenoma

• Hypertrophy: primary precocious puberty, primary hypothyroidism

• Lymphocytic hypophysitis

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• Infection

• Severe dural AV fistula

Complex Sellar / Parasellar Cyst

• Cystic craniopharyngeoma

• Hemorrhagic pituitary adenoma

• Hemorrhagic / proteinaceous Rathke cleft cyst

Intrasellar Mass

• Pituitary adenoma / carcinoma (most common cause)

• Craniopharyngioma (2nd most common cause)

• Meningioma: from surface of diaphragm / tuberculum sellae

• Chordoma

• Metastasis: lung, breast, prostate, kidney, GI tract, spread from nasopharynx

• Intracavernous ICA aneurysm: bilateral in 25%

• Pituitary abscess: rapidly expanding mass associated with meningitis

• Empty sella

• Rathke cleft cyst: commonly at junction of anterior + posterior pituitary gland

• Granular cell tumor = myeloblastoma: benign neoplasm of posterior pituitary gland

• Granuloma: sarcoidosis, giant cell granuloma, TB, syphilis, eosinophilic granuloma

• Lymphoid adenohypophysitis

• Pituitary hyperplasia, eg, in Nelson syndrome

Hypointense Lesion of Sella

• Empty sella

• Pituitary stone (= pituilith)

  • = sequelae of autonecrosis of pituitary adenoma

• Intrasellar aneurysm

• Persistent trigeminal artery

• Calcified meningioma

• Pituitary hemochromatosis (anterior pituitary lobe only)

Parasellar Mass

• Meningioma: tentorium cerebelli

• Neurinoma (III, IV, V₁, V₂, VI)

• Metastasis: lung, breast, kidney, GI tract, spread from nasopharynx

• Epidermoid

• Aneurysm

• Carotid-cavernous fistula

Suprasellar Mass

• Meningioma

• Craniopharyngioma: in 80% suprasellar

• Chiasmal + optic nerve glioma

  • in 38% of neurofibromatosis; adolescent girls;

  • DDx: chiasmal neuritis

• Hypothalamic glioma

• Hamartoma of tuber cinereum

• Infundibular tumor

  • metastasis (esp. breast); glioma; lymphoma / leukemia; histiocytosis X; sarcoidosis, tuberculosis

  • diameter of infundibulum >4.5 mm immediately above level of dorsum; cone-shaped (on coronal scan)

• Germinoma

  • = malignant tumor similar to seminoma (= ectopic pinealoma )

  • frequently calcified (teratoma)

  • CSF spread (germinoma + teratocarcinoma)

  • enhancement on CECT (common)

• Epidermoid / dermoid

  • cystic lesion containing calcifications + fat

  • minimal / no contrast enhancement

• Arachnoid cyst

  • hydrocephalus (common), visual impairment

  • endocrine dysfunction

  • Age: most common in infancy

• Enlarged 3rd ventricle extending into pituitary fossa

• Suprasellar aneurysm

  • rim calcification + eccentric position

Suprasellar Mass in Adulthood

mnemonic: SATCHMO

• Sarcoidosis, Sella neoplasm with superior extension

• Aneurysm (ectatic carotid, carotid-cavernous sinus fistula), Arachnoid cyst, Adenoma (pituitary)

• Tuberculosis, Teratoma: dysgerminoma (usually), dermoid, epidermoid

• Craniopharyngioma, Chordoma

• Hypothalamic glioma, Histiocytoma, Hamartoma

• Meningioma, Metastatic disease, Mucocele

• Optic nerve glioma, neuroma

Suprasellar Mass with Low Attenuation

• Craniopharyngioma

• Dermoid / epidermoid

• Arachnoid cyst

• Lipoma

• Simple pituitary cyst

• Glioma of hypothalamus

Suprasellar Low-density Lesion with Hydrocephalus

• CYST

  • Arachnoid cyst

  • Ependymal cyst of 3rd ventricle

  • Parasitic cyst of 3rd ventricle (cysticercosis)

  • Dilated 3rd ventricle (in aqueductal stenosis)

• CYSTIC MASS

  • Epidermoid

  • Hypothalamic pilocytic astrocytoma

  • Cystic craniopharyngioma

N.B.: Cystic lesion may be inapparent within surrounding CSF; metrizamide cisternography is helpful in detection + to exclude aqueduct stenosis

Suprasellar Mass with Mixed Attenuation

• IN CHILDREN

  • Hypothalamic-chiasmatic glioma

  • Craniopharyngioma

  • Hamartoma of tuber cinereum

  • Histiocytosis

• IN ADULTS

  • Suprasellar extension of pituitary adenoma

  • Craniopharyngioma

  • Epidermoid cyst

  • Thrombosed aneurysm

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  • Low-grade hypothalamic / optic glioma

  • Inflammatory lesion: sarcoidosis, TB, sphenoid mucocele

Suprasellar Mass with Calcification

• CURVILINEAR

  • Giant carotid aneurysm

  • Craniopharyngioma

• GRANULAR

  • Craniopharyngioma

  • Meningioma

  • Granuloma

  • Dermoid cyst / teratoma

  • Optic / hypothalamic glioma (rare)

Suprasellar Mass with T1 Shortening (Hyperintensity)

• Craniopharyngeoma

  • viscous material in cystic region (protein concentration of 10-30%)

  • intrasellar component in 70%

• Germinoma

  • containing hemorrhage (methemoglobin)

  • most common in adolescent girls

  • diabetes insipidus

• Thrombosed aneurysm

  • laminated internal architecture due to thrombus of differing age (best appreciated on T2)

• Rathke's cleft cyst

  • containing thickly mucinous material

  • no contrast enhancement

  • intra- / suprasellar in location

• Dermoid cyst

  • with predominantly sebaceous material

  • suppressed by fat saturation scan

• Lipoma at floor of 3^rd ventricle

  • round + homogeneous

  • suppressed by fat saturation scan

• Ectopic neurohypophysis

  • along floor of 3^rd ventricle

  • quite small

• Cavernous angioma

  • = collection of sinusoidal spaces

  • occasionally familial

  • multinodular popcorn aggregate with central zones of T1-shortening surrounded by rind of T2-shortening

  • frequently multiple

  • angiographically occult /cryptic

• Hemorrhagic metastasis

Suprasellar Mass with Uniform Enhancement

• Pituitary adenoma

• Pituitary hyperplasia

  • symmetrical masslike contour

  • appropriate clinical setting (hypothyroidism, pregnancy)

• Meningioma

  • midline suprasellar lesion

• Lymphocytic adenohypophysitis

  • usually in women during postpartum period

  • diabetes insipidus common

    • suprasellar extension common

• Chiasmatic / hypothalamic glioma

• Unusual craniopharyngeoma

• Langerhans histiocytosis

• Germinoma

Enhancing Supra- and Intrasellar Mass

• Pituitary adenoma

• Meningioma

• Germinoma

• Hypothalamic glioma

• Craniopharyngioma

Perisellar Vascular Lesion

• ICA aneurysm

  • Giant aneurysms are >2.5 cm in diameter

  • destruction of bony sella / superior orbital fissure

  • calcified wall / thrombus

  • CECT enhancement, nonuniform with thrombosis

• Ectatic carotid artery

  • curvilinear calcifications

  • encroachment upon sella turcica

• Carotid-cavernous sinus fistula

Lesion Expanding Cavernous Sinus

• TUMOR

  • Trigeminal schwannoma

  • Pituitary adenoma

  • Parasellar meningioma

  • Parasellar metastasis

  • Invasion by tumor of skull base

• VESSEL

  • Internal carotid artery aneurysm

  • Carotid-cavernous fistula

  • Cavernous sinus thrombosis

• TOLOSA-HUNT SYNDROME

  • = granulomatous invasion of cavernous sinus

Pineal gland

Classification of Pineal Gland Tumors

Incidence of pineal mass:

• <1% of all intracranial tumors, 4% of all childhood intracranial masses, 9% of all intracranial masses in Asia

• PRIMARY TUMOR

  • Germ cell origin (2/3)

    • forming embryonic tissue

      • Germinoma (40 50%)

      • Embryonal cell carcinoma

      • Teratoma (15%): benign mature teratoma, benign immature teratoma, malignant teratoma

    • forming extraembryonic tissue

      • 4. Choriocarcinoma (<5%)

      • 5. Endodermal sinus tumor = yolk sac tumor

  • Pineal parenchymal cell origin (<15%)

    • Pineocytoma

    • Pineoblastoma

  • Other cell origin

    • Retinoblastoma (trilateral retinoblastoma = left eye + right eye + pineal gland

    • Astrocytoma

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    • Ependymoma

    • Meningioma

    • Hemangiopericytoma

    • Pineal + tectal glioma

    • Cavernous hemangioma

    • Meningioma

  • Cysts

    • Pineal cyst

    • Malignant teratoma

    • AVM, vein of Galen aneurysm

    • Arachnoid cyst

    • Inclusion cyst (dermoid / epidermoid)

• SECONDARY TUMOR

Metastasis: eg, lung carcinoma

DDx considerations:

female: likely NOT germ cell tumor

hypodense matrix: likely NOT pineal cell tumor

distinct tumor margins: probably pineocytoma / teratoma / germinoma

calcification: likely NOT teratocarcinoma, metastasis, germinoma

CSF seeding: NOT teratoma

intense enhancement: likely NOT teratoma

Serum markers:

choriocarcinoma -HCG

embryonal cell carcinoma -FP and -HCG

endodermal sinus tumor -FP

teratoma -HCG and -FP

germinoma placental alkaline phosphatase

Intensely Enhancing Mass in Pineal Region

• Germinoma

• Pineocytoma / -blastoma

• Pineal teratocarcinoma

• Glioma of brainstem / thalamus

• Subsplenial meningioma

• Vein of Galen aneurysm

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Anatomy of Brain

Embryology

Neurulation

neural plate = CNS originates as a plate of thickened ectoderm on the dorsal aspect of the embryo

neural crest = elevation of the lateral margins of the neural plate; forms the peripheral nervous system

neural tube = invagination between the two neural crests; its wall forms the brain + spinal cord; its lumen forms the ventricles + spinal canal

4.6 weeks MA: formation of neural tube

5.6 weeks MA: rostral neuropore closes

5.9 weeks MA: caudal neuropore closes

6.0 weeks MA: 3 primary brain vesicles develop (prosencephalon, mesencephalon, rhombencephalon) development of cervical flexure

7.0 weeks MA: 2 additional primary brain vesicles form out of rhombencephalon (pontine flexure divides into myelencephalon, metencephalon)

15 weeks MA: dorsal portion of alar plates bulging into 4th ventricle have fused in midline to form cerebellar vermis

Brain Growth

• = increase in thickness of brain mantle with relative constant ventricular width

• Most rapid brain growth from 12 to 24 weeks MA!

Neuronal Migration

7th  week subependymal neuronal proliferation = germinal matrix

8th  week radial migration to cortex along radial glial fibers

Sagittal Section through Brain at 10 11 Weeks GA

Myelination

Progression:  caudal to cranial; posterior to anterior

MR:  T1WI if <7 months of age; T2WI if >7 months of age

• Milestones:

  term birth:	brainstem, cerebellum, posterior limb of internal capsule
  2 months:	anterior limb of internal capsule
  3 months:	splenium of corpus callosum
  6 months:	genu of corpus callosum

• Occipital white matter:

  • central at 5 months (T1WI), 14 months (T2WI)

  • peripheral at 7 months (T1WI), 15 months (T2WI)

• Frontal white matter:

  • central at 6 months (T1WI), 16 months (T2WI)

  • peripheral at 11 months (T1WI), 18 months (T2WI)

Classification of brain anatomy

• PROSENCEPHALON = forebrain

  • cerebrum, lateral ventricles, choroid, thalami, cerebellum sonographically visible at 12 weeks MA

  • Telencephalon = cerebrum =  cerebral hemispheres, putamen, caudate nucleus

  • Diencephalon

    • =  thalamus, hypothalamus, epithalamus (= pineal gland + habenula), globus pallidus

• MESENCEPHALON = midbrain

  • =  short segment of brainstem above pons; traverses the hiatus in tentorium cerebelli; contains cerebral peduncles, tectum, colliculi (corpora quadrigemina)

• RHOMBENCEPHALON = hindbrain

  • posterior cystic space of 4th ventricle sonogra-phically detectable between 8 and 10 weeks MA

  • Metencephalon = cerebellar hemispheres, vermis

  • Myelencephalon = medulla oblongata, pons

• BRAINSTEM = mesencephalon + myelencephalon contains

  • cranial nerve nuclei

  • sensory and motor tracts between thalamus, cerebral cortex, and spinal cord

  • reticular formation controlling respiration, blood pressure, gastrointestinal function, centers for arousal and wakefulness

Scalp

The outer 3 layers are often torn off as a unit in accidents; wounds do not gape if epicranius not involved

• SKIN

• SUBCUTIS

  • =  fibroadipose tissue closely adherent to skin and underlying epicranius

• EPICRANIUS + GALEA APONEUROTICA

  • = occipitofrontal + temporoparietal muscles forming centrally the epicranial aponeurosis

• SUBGALEAL SPACE

  • = subaponeurotic areolar tissue between periosteum of outer table and galea

• PERICRANIUM = periosteum of outer table

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• SUBPERIOSTEAL SPACE

  • =  created when periosteum of outer table becomes detached from calvaria (= cephalohematoma)

  

  Meninges of Brain

Meninges of brain

• CALVARIA = upper part of cranium enclosing the brain

  • outer table of resilient compact bone

  • diplo = trabecular bone containing red bone marrow

  • inner table of thin and brittle compact bone

• EPIDURAL SPACE

  • =  created when outer layer of dura (periosteum of inner table) becomes detached from calvaria

• PACHYMENINGES = DURA MATER

  • outer dural layer

    • = highly vascularized periosteum of inner table

  • space for venous sinuses

  • inner dural layer

    • = meningeal layer derived from meninx

• SUBDURAL SPACE

  • =  cleft formed in pathologic states within inner layer of dura

• LEPTOMENINGES

  • Arachnoid

    • =  closely applied to inner surface of dura

  • Subarachnoid space

    • Histo:  fine connective tissue + cellular septa link pia and arachnoid

    •   contains CSF that drains through the valves of arachnoid granulations into venous sinuses

    •   forms basal cisterns

  • Pia mater

• SUBPIAL SPACE

  • =  perivascular (Virchow-Robin) space

• EPENDYMA

Cerebrospinal fluid

• Total volume:

  • 50 mL in newborn, 150 mL in adult

• Composition:

  • inorganic salts like those in plasma, traces of protein + glucose

• Production:

  • 0.3 0.4 mL/min resulting in 500 mL/day; secreted into ventricles by choroid plexuses (80 90%), 10 20% formed by parenchyma of the cerebrum + spinal cord

• Circulation:

  • from ventricles through foramina of Magendie + Luschka of 4th ventricle into cisterna magna + basilar cisterns; 80% of CSF flows initially into suprasellar cistern + cistern of lamina terminalis, the ambient / superior cerebellar cisterns, eventually ascending over superolateral aspects of each hemisphere; 20% initially enters spinal subarachnoid space + eventually recirculates into cerebral subarachnoid space

• Absorption:

  into venous system by

  • arachnoid villi of superior sagittal sinus (villi behave as one-way valves with an opening pressure between 20 50 mm of CSF)

  • cranial + spinal nerves with eventual absorption by lymphatics (50%)

  • prelymphatic channels of capillaries within brain parenchyma

  • vertebral venous plexuses, intervertebral veins, posterior intercostal + upper lumbar veins into azygos + hemiazygos veins

• Opening pressure:  80 180 mm H₂O

Cerebral Aqueduct

• pulsatile flow (due to brain motion during cardiac cycle) + net outflow into 4th ventricle; diameter of 2.6 4.2 mm; peak outflow velocity of 6 51 mm/sec; inflow velocity of 3 28 mm/sec

Septum pellucidum

• =  two thin vertical sheets of glia-like elements that abut each other in the midline with a potential space between them separating right from left frontal horn; slitlike cavity (in 10%) = 5th ventricle

• Borders:

  below:	column + body of fornix
  above:	corpus callosum
  ventral:	continuous with precomissural septum + subcallosal gyrus

Basal nuclei

= BASAL GANGLIA (earlier incorrect designation)

• Amygdaloid body

• Claustrum

• Corpus striatum

  • Caudate

  • Lentiform nucleus

    • pallidum = globus pallidus

    • putamen

Pituitary gland

=  hypophysis CEREBRI within hypophyseal fossa of sphenoid, covered superiorly by sellar diaphragm (= dura mater) which has an aperture for the infundibulum centrally

Cavernous Sinus

(coronal view)

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Coronal Section through Anterior Commissure

Axial Section through Level of Third ventricle

Coronal Section through Ventral Part of Pons

Size:  

• adult size is achieved at puberty

• Height in adult females  =  7 (range 4 10) mm

• Height in adult males  =  5 (range 3 7) mm

Shape:

• flat / downwardly convex superior border

• upwardly convex during puberty, pregnancy, in hypothyroidism (due to hyperplasia)

Anterior Lobe of Pituitary Gland

• =  larger anterior portion of adenohypophysis comprising 80% of pituitary gland volume

• Origin:  ectodermal derivative of stomadeum

• Function:  

  • chromophil cells

    • acidophil cells = cells

      • growth hormone = somatotropin (STH), prolactin = lactogenic hormone (LTH)

    • basophil cells = cells

      • adrenocorticotropin = adrenocorticotropic hormone (ACTH), thyrotropin = thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), interstitial-cell-stimulating hormone (ICSH), luteinizing hormone (LH), melanocyte-stimulating hormone (MSH)

  • chromophobe cells = 50% of epithelial cell population, of unknown significance

• MRI:

  • larger homogeneous component isointense to white matter on T1WI + T2WI

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  • prominent contrast enhancement (during first 3 minutes) due to lack of blood-brain barrier

  • hyperintense in the newborn fading to normal adult signal by 2nd month of life

Pars Intermedia of Pituitary Gland

• =  posterior portion of adenohypophysis; separated from anterior lobe by hypophyseal cleft in fetal life

• Origin:  Rathke cleft / pouch within intermediate lobe of pituitary gland

• Function:  termination point of short hypothalamic axons elaborating tropic hormones (= releasing factors + prolactin inhibiting factor), which are carried to anterior lobe via the portal system

• not visible with imaging techniques

Posterior Lobe of Pituitary Gland

• =  major portion of neurohypophysis

  

  Cranial Nuclei of Brainstem and Reticular Formation

  A  =  sleep, wakefulness, consciousness

  B  =  visual spatial orientation, higher autonomic coordination of food intake

  C  =  pneumotaxic center, coordination of breathing and circulation

  D  =  swallowing

  E  =  blood pressure, cardiac activity, vascular tone

  F  =  expiration

  G  =  area postrema = trigger zone for vomiting

  H  =  inspiration

• Origin:  diencephalic outgrowth (termination point of axons from supraoptic + paraventricular nuclei of hypothalamus)

• Function:  storage site for vasopressin (= antidiuretic hormone [ADH]) + oxytocin transported from paraventricular + supraoptic nuclei of hypothalamus along neurosecretory hypothalamohypophyseal tract

• MRI:

  • hyperintense on T1WI + isointense on T2WI in comparison with anterior lobe (? due to relaxing agent of phospholipid / neurosecretory granules / vasopressin)

  • isointense in 10% of normal individuals

Pituitary Stalk / Infundibulum

• arises from anterior aspect of floor of 3rd ventricle (infundibular recess)

• Histo:  formed from axons of cells lying in supraoptic + paraventricular nuclei of hypothalamus

• joins posterior lobe at junction of anterior + posterior lobes

• up to 3 mm thick superiorly, up to 2 mm thick inferiorly

• usually in midline, may be slightly tilted to one side

• MRI:

  • prominent contrast enhancement

Pineal gland

• Development:

  • from area of ependymal thickening at the most caudal portion of roof of 3rd ventricle that evaginates into a pinecone-shaped mass during 7th week of gestation; initially contains ependyma lining in central cavity that connects with 3rd ventricle

• Function:  

  • Regulation of long-term biologic rhythm (eg, onset of puberty)

  • Regulation of short-term biologic rhythm (eg, diurnal / circadian) due to photoperiodic clues via accessory optic pathway

• Histo:

  • pinealocytes with dendritic processes (= neuronal cells) make up 95% of population

  • neuroglial supporting cells make up 5% of population

• Location:  attached to upper aspect of posterior border of 3rd ventricle, lies within CSF of quadrigeminal cistern, anterior to pineal gland is cistern of velum interpositum (= cistern of transverse fissure)

• Size:  8 mm long, 4 mm wide

Trigeminal nerve (V)

• Nuclei:  

  • mesencephalic nucleus: proprioception extends to level of inferior colliculus

  • main sensory nucleus: tactile sensation

  • motor nucleus: motor innervation

  • spinal nucleus: pain + temperature sensation extends to level of 2nd cervical vertebra

• Location:  in tegmentum of lateral pons, along anterolateral aspect of 4th ventricle

• Course:  

  • through prepontine cistern

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  • exits through porus trigeminus (= opening in dura)

  • enters Meckel cave with dura mater + leptomeninges forming trigeminal cistern (= CSF-filled subarachnoid space) at the most anteromedial portion of the petrous pyramid

  • forms gasserian ganglion (= trigeminal ganglion), which contains cell bodies of sensory fibers except those for proprioception

  

  Trigeminal Nerve

• Trifurcation into 3 principal branches:

  • ophthalmic nerve (V₁)

    • Course:  in lateral wall of cavernous sinus

    • Exit:  superior orbital fissure

    • Supply:  sensory innervation of scalp, forehead, nose, globe

    • mediates afferent aspect of corneal reflex

  • maxillary nerve (V₂)

    • Course:  between lateral dural wall of cavernous sinus + skull base

    • Exit:  through foramen rotundum into pterygopalatine fossa

    • Supply:  sensory innervation of middle third of face, upper teeth

    • Main trunk:  infraorbital nerve

  • mandibular nerve (V₃)

    • Course:  NOT through cavernous sinus

    • Exit:  through foramen ovale into masticator space

    • Supply:

      • sensory innervation of lower third of face, tongue, floor of mouth, jaw

      • motor innervation of muscles of mastication (masseter, temporalis, medial + lateral pterygoid), mylohyoid m., anterior belly of digastric m., tensor tympani m., tensor veli palatini m.

Facial nerve (VII)

• Function:  

  • Lacrimation (via greater superficial petrosal nerve)

  • Stapedius reflex: sound damping

  • Taste of anterior 2/3 of tongue (via chorda tympani nerve to lingual nerve)

  • Facial expression (platysma)

    

    Segmental Anatomy of Facial Nerve Intracranially

    (viewed from anteriorly)

  • Secretion of lacrimal + submandibular + sublingual glands (via nervus intermedius)

• Nuclei:  

  • Motor nucleus: ventrolateral deep in reticular formation of the caudal part of the pons

    • Intrapontine course:

      • dorsomedially towards 4th ventricle

      • curving anterolaterally around upper pole of abducens nucleus (= geniculum)

      • descending anterolaterally through reticular formation

    • Innervation to:  stapedius m., stylohyoid m., posterior belly of digastric m., occipitalis m., buccinator, muscles of facial expression, platysma

  • Nucleus solitarius (sensory nucleus):

    • nervus intermedius: sensation from anterior 2/3 of tongue, skin on + adjacent to ear

    

    Internal Auditory Canal

    Posterior wall of IAC is removed; cross sections through IAC are displayed above; A = anterior, P = posterior

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  • Superior salivatory nucleus (parasympathetic secretomotor innervation)

    • greater petrosal n.: secretion of lacrimal glands, nasal cavity, paranasal sinuses

    • chorda tympani: submandibular gland, sublingual glands

• Course & Segments:

  • intracranial segment

    • from brainstem to porus acusticus internus:

    •   pontine segment: motor root fibers of facial n. hook around the abducens nucleus forming the facial colliculus (= elevation in the floor of the 4th ventricle); the nerve continues laterally from the corticospinal tract

    •   cisternal segment: facial n. emerges from lateral aspect of pontomedullary junction + courses anterolaterally in cerebellopontine angle cistern to internal auditory canal (IAC)

  • intracanalicular segment

    • =  motor root of facial n. within internal auditory canal in anterosuperior groove of vestibulocochlear n. with nervus intermedius between them

      mnemonic:  seven up

  • labyrinthine segment

    • short segment of facial n. travels within its own bony canal (= fallopian canal) curving anteriorly over top of cochlea; terminates in anteromedial genu (geniculate ganglion)

  • tympanic segment

    • =  segment from anterior to posterior genu just underneath lateral semicircular canal

    •   horizontal segment: facial n. makes a 130 turn posteriorly and horizontally along medial wall of mesotympanum lateral to vestibule between lateral semicircular canal (above) and oval window (below)

    •   pyramidal segment: facial n. turns inferiorly at second genu in pyramidal eminence; gives off the nerve for the stapedius muscle

  • mastoid segment

    • facial n. descends from posterior genu through anterior mastoid (= medial wall of aditus ad antrum) and gives off chorda tympani just prior to exit from skull base through stylomastoid foramen

  • parotid / extracranial segment

    • facial n. travels forward between superficial + deep lobes of parotid gland lateral to styloid process + external carotid a. + retromandibular v.

• Branches:  

  • Greater superficial petrosal nerve (parasympathetic + motor fibers) arises from geniculate ganglion, runs anteromedially, and exits at the facial hiatus on the anterior surface of the temporal bone + passes under Meckel cave near foramen lacerum

    •   forms vidian nerve after receiving sympathetic fibers from deep petrosal nerve, which surrounds the internal carotid artery

  • Stapedial nerve (motor fibers) arises from proximal descending facial n.

  • Chorda tympani (sensory + parasympathetic fibers) leaves facial n. about 6 mm above stylomastoid foramen

    •   ascends forward in a bony canal (= posterior canaliculus)

    •   perforates posterior wall of tympanic cavity

    •   crosses medial to handle of the malleolus underneath mucosa of tympanic cavity

    •   reenters bone at medial end of petrotympanic fissure (= posterior canaliculus)

    •   joins the lingual nerve (= branch of V₃) containing sensory fibers from anterior 2/3 of tongue + secretomotor fibers for submandibular and sublingual glands

Perihippocampal fissures

• Transverse fissure of Bichat

  • =  lateral extension of perimesencephalic cistern separating thalamus superiorly from parahippocampal gyrus inferiorly

• Choroidal fissure

  • =  superior lateral extension of transverse fissure extending superior to hippocampus

• Hippocampal fissure

  • =  inferior lateral extension of transverse fissure extending between hippocampus and parahippocampal gyrus

• Temporal horn of lateral ventricle

  • =  lateral margin of hippocampus; separated from transverse fissure by fimbria + choroid plexus

  • Does not communicate with transverse fissure

Cerebral vessels

Common Carotid Artery

• 70% of blood flow is delivered to ICA

• shares waveform characteristics of both internal + external carotid arteries

• velocity increases toward the aorta (9 cm/sec for each cm of distance from the carotid bifurcation)

Carotid Bifurcation

= physiologic stenosis due to inertial forces of blood flow diverting main-flow stream from midvessel to a path along vessel margin at flow divider

Coronal Section through Right Mesial Temporal Lobe

(CA1 through CA4 = hippocampus)

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Location:  lateral to upper border of thyroid cartilage; at level of C3-4 intervertebral disk

Branches:  ECA arises anterior + medial to ICA (95%)

External Carotid Artery Branches

mnemonic:  All Summer Long Emily Ogled Peter's Sporty Isuzu

• Ascending pharyngeal artery

• Superior thyroid artery

• Lingual artery

• External maxillary = facial artery

• Occipital artery

• Posterior auricular artery

• Superficial temporal artery

• Internal maxillary artery

Internal Carotid Artery

• CERVICAL SEGMENT

  • ascends posterior and medial to ECA; enters carotid canal of petrous bone; NO branches

    Carotid bulb = carotid sinus:

    • =  dilated proximal part of ICA with thinner media + thicker adventitia containing many receptor endings of glossopharyngeal nerve

    • Function:  baroreceptor responsive to changes in arterial blood pressure

    • hypersensitive carotid sinus

      • =  slight touch / head movement initiates

      • (a) vasodilatation with drop in blood pressure

      • (b) vagal stimulation with sinoatrial / atrioventricular cardiac block

    • stagnant eddy that rotates at outer vessel margin

• PETROUS SEGMENT

  • ascends briefly, in carotid canal bends anteromedially in a horizontal course (anterior to tympanic cavity + cochlea); exits near petrous apex through posterior portion of foramen lacerum; ascends to juxtasellar location where it pierces dural layer of cavernous sinus

    

    Circle of Willis

    • Branches:

      • Caroticotympanic a.: to tympanic cavity, anastomoses with anterior tympanic branch of maxillary a. + stylomastoid a.

      • Pterygoid (vidian) a.: through pterygoid canal; anastomoses with recurrent branch of greater palatine a.

• CAVERNOUS SEGMENT

  • ascends to posterior clinoid process, then turns anteriorly + superomedially through cavernous sinus; exits medial to anterior clinoid process piercing dura

    Branches:

    • Meningohypophyseal trunk

      • tentorial branch

      • dorsal meningeal branch

      • inferior hypophyseal branch

    • Anterior meningeal a.: supplies dura of anterior fossa; anastomoses with meningeal branch of posterior ethmoidal a.

    • Cavernous rami supply trigeminal ganglion, walls of cavernous + inferior petrosal sinuses

• SUPRACLINOID SEGMENT

  • ascends posterior + lateral between oculomotor + optic nerve

    Branches:

    • mnemonic:  OPA

      • Ophthalmic a.

      • Posterior communicating a.

      • Anterior choroidal a.

    • Ophthalmic a. exits from ICA medial to anterior clinoid process, travels through optic canal inferolateral to optic nerve

      • recurrent meningeal branch: dura of anterior middle cranial fossa

      • posterior ethmoidal a.: supplies dura of planum sphenoidale

      • anterior ethmoidal a.

    • Superior hypophyseal a.: optic chiasm, anterior lobe of pituitary

    • Posterior communicating a. (pCom)

    • Anterior choroidal a.

    • Middle + anterior cerebral arteries (MCA, ACA)

Carotid Siphon

Flow direction:  C4 C1

(a) C4 segment =	before origin of ophthalmic a.
(b) C3 segment =	genu of ICA
(c) C2 segment =	supraclinoid segment after origin of ophthalmic a.
(d) C1 segment =	terminal segment of ICA between pCom + ACA

Anterior Cerebral Artery (ACA)

• A1 (horizontal) segment between origin and anterior communicating a. (aCom)

  • inferior branches

    • supply superior surface of optic nerve + chiasm

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  • superior branches

    • penetrate brain to supply anterior hypothalamus, septum pellucidum, anterior commissure, fornix columns, anterior inferior portion of corpus striatum

  • medial lenticulostriate artery = largest striatal artery = recurrent artery of Heubner for anteroinferior portion of head of caudate, putamen, anterior limb of internal capsule)

• A2 (interhemispheric) segment after origin of anterior communicating a. (aCom); ascends in cistern of lamina terminalis

  Branches:

  • Medial orbitofrontal a.: along gyrus rectus

  • Frontopolar a.

  • Callosomarginal a.: within cingulus gyrus

  • Pericallosal a.: over corpus callosum within callosal cistern

    • Superior internal parietal a.: anterior portion of precuneus + convexity of superior parietal lobule

    • Inferior internal parietal a.

    • Posterior pericallosal a.

      • from callosomarginal / pericallosal artery:

      •   Anterior + middle + posterior internal frontal aa.

      •   Paracentral a.: supplies precentral + postcentral gyri

• Supply:  anterior 2/3 of medial cerebral surface + 1 cm of superomedial brain over convexity

Middle Cerebral Artery

• =  largest branch of ICA arising lateral to optic chiasm

• M1 (horizontal) segment = courses in lateral direction

  • Branches:  lateral lenticulostriate aa.

  • Supply:  part of head and body of caudate, globus pallidus, putamen, and posterior limb of internal capsule

• M2 (sylvian) segment = enters sylvian fissure just ventral to anterior perforated substance; divides into superior and inferior divisions with 2 / 3 / 4 branches

  • Branches:  temporal lobe and insular cortex (sensory language area of Wernicke), parietal lobe (sensory cortical areas), inferolateral frontal lobe

• M3 (cortical) segment = distal branches lateral to insular cortex = candelabra [candelabrum, Latin = decorative candlestick / lamp with several arms or branches]

• Branches:

  •   Anterior temporal a.

  • Ascending frontal a. / prefrontal a.

  • Precentral a. = pre-Rolandic a.

  • Central a. = Rolandic a.

  • Anterior parietal a. = post-Rolandic a.

  • Posterior parietal a.

  • Angular a.

  • Middle temporal a.

  • Posterior temporal a.

  • Temporo-occipital a.

• Supply:  lateral cerebrum, insula, anterior + lateral temporal lobe

Posterior Cerebral Artery

originates from bifurcation of basilar artery within inter-peduncular cistern (in 15% as a direct continuation of posterior communicating artery); lies above oculomotor nerve and circles midbrain above the tentorium cerebelli

• Branches:  

  • Mesencephalic perforating branches: tectum + cerebral peduncles

  • Posterior thalamoperforating aa.: midline of thalamus + hypothalamus

  • Thalamogeniculate aa.: geniculate bodies + pulvinar

  • Posterior medial choroidal a.: circles midbrain parallel to PCA; enters lateral aspect of quadrigeminal cistern; passes laterally and above pineal gland and enters roof of 3rd ventricle; supplies quadrigeminal plate + pineal gland

  • Posterior lateral choroidal a.: courses laterally and enters choroidal fissure; anterior branch to temporal horn + posterior branch to choroid plexus of trigone and lateral ventricle + lateral geniculate body

  • Cortical branches:

    • Anterior inferior temporal a.

    • Posterior inferior temporal a.

    • Parieto-occipital a.

    • (d)  Calcarine a.

    • (e)  Posterior pericallosal a.

• Supply:  medial + posterior temporal lobe, medial parietal lobe, occipital lobe

Arterial Anastomoses of the Brain

Anastomoses via Arteries at the Base of the Brain

• Circle of Willis

  • Right ICA right ACA aCom left ACA left ICA

  • ICA pCom basilar a.

  • ICA anterior choroidal a. posterior choroidal a. PCA basilar a.

• Developmental anomaly

  • three transient embryonal carotid-basilar anastomoses appearing consecutively in fetal life:

    • Primitive hypoglossal artery

      • =  arterial connection between the intrapetrosal portion of ICA and proximal portion of basilar a.

    • Primitive acoustic (otic) artery

      • =  arterial connection between cervical portion of ICA + vertebral artery in region of 12th nerve

    • Persistent primitive trigeminal artery

      Incidence:  1 2 / 1,000 angiograms

      •   short wide connection between the cavernous portion of ICA and upper third of basilar artery (beneath posterior communicating artery)

      • enlargement of ipsilateral ICA

      • ectopic vessel crossing the pontine cistern to anastomose with basilar artery

Anastomoses via Surface Vessels

• Leptomeningeal anastomoses of the cerebrum:ACA MCA PCA

• Leptomeningeal anastomoses of the cerebellum:Superior cerebellar a. AICA PICA

P.259

Rete Mirabile

• ECA middle meningeal a. / superficial temporal a. leptomeningeal aa. ACA / MCA

Ophthalmic Artery

Cerebral Veins

Important vascular markers:

• Pontomesencephalic v. = anterior border of brainstem

• Precentral cerebellar v. = position of tectum

  • Colliculocentral point = midpoint of Twining's line at knee of precentral cerebellar vein

  

  Cerebral Veins

• Venous angle = acute angle at junction of thalamostriate with internal cerebral v. = posterior aspect of foramen of Monro

• Internal cerebral vv. = demarcate caudad border of splenium of corpus callosum superiorly + pineal gland inferiorly

• Copular point = junction of inferior + superior retrotonsillar tributaries draining cerebellar tonsils in region of copular pyramids of vermis

Anastomoses between ICA and ECA and Vertebral Artery

P.260

Cerebellar vessels

Vertebral Artery

originates from subclavian a. proximal to thyrocervical trunk; left vertebral a. usually greater than right cerebral a.; left vertebral a. may originate directly from aorta (5%)

• PREVERTEBRAL SEGMENT

  • ascends posterosuperiorly between longus colli + anterior scalene muscle; enters transverse foramina at C6

  • Branches:  muscular branches

• CERVICAL SEGMENT

  • ascends through transverse foramina in close proximity to uncinate processes

  • Branches:

    • Anterior meningeal a.

• ATLANTIC SEGMENT

  • exits transverse foramen of atlas; passes posteriorly in a groove on superior surface of posterior arch of atlas; pierces atlanto-occipital membrane + dura mater to enter cranial cavity

  • Branches:

    • Posterior meningeal branch to posterior falx + tentorium

• INTRACRANIAL SEGMENT

  • ascends anteriorly + laterally around medulla to reach midline at pontomedullary junction; anastomoses with contralateral side to form basilar artery at clivus

  • Branches:

    • Anterior + posterior spinal a.

    • Posterior inferior cerebellar a. (PICA)

    • Anterior inferior cerebellar a. (AICA)

    • Internal auditory a.

    • Superior cerebellar a.

    • Posterior cerebral a. (PCA)

    • Medullary + pontine perforating branches

    •   May terminate in common AICA-PICA trunk

  

  Arterial Supply of the Cerebellum - Lateral View

Anterior Inferior Cerebellar Artery

• =  AICA = first branch of basilar artery

• Supply:

  lateroinferior part of pons, middle cerebellar peduncle, floccular region, anterior petrosal surface of cerebellar hemisphere

• Quite variable course + vascular supply with reciprocal relation between vascular territories of AICA + PICA!

Posterior Inferior Cerebellar Artery

• =  PICA = last and largest branch of vertebral artery

• Supply:

  inferoposterior surface of cerebellar hemisphere adjacent to occipital bone, ipsilateral part of inferior vermis, inferior portion of deep white matter only

• Parts:  

  • Premedullar segment = caudal loop around medulla, may descend below level of foramen magnum

  • Retromedullar segment = ascending portion up to the level of 4th ventricle and tonsils

  • Supratonsillar segment = the most cranial point is the choroidal point

  • P1 segment =  horizontal segment between origin of PICA + pCom

  • P2 segment =  segment downstream from pCom take-off

• Variations:  commonly asymmetric; hypoplastic / absent in 20% [vascular supply then provided by anterior inferior cerebellar artery (AICA)]

• Orthotopic choroid point established by:  

  • perpendicular line from choroid point onto Twining's line = TTT-line (Twining's Tuberculum-Torcular line) bisects TTT-line (length of anterior portion 52 60%)

  • perpendicular line from choroid point cuts CT-line (Clivus-Torcular line) <1 mm anterior / <3 mm posterior to junction of anterior and middle thirds of CT-line

Arterial Supply of the Cerebellum - Inferior View

P.261

Superior Cerebellar Artery

• =  SCA = last but one branch of basilar artery

• Supply:

  superior aspect of cerebellar hemisphere (tentorial surface), ipsilateral superior vermis, largest part of deep white matter including dentate nucleus, pons

Posterior Inferior Cerebellar Artery

1,2 = lines to establish orthotopic choroid point (see text)

Vascular Territories of Cerebellum

Vascular Territories of Brainstem

P.262

P.263

Brain Disorders

Abscess of Brain

Pyogenic Abscess

• = focal area of necrosis beginning in area of cerebritis with formation of surrounding membrane

Cause:

• Extension from paranasal sinus infection (41%) / mastoiditis / otitis media (5%) / facial soft-tissue infection / dental abscess

• Generalized septicemia (32%):

  • lung (most common): bronchiectasis, empyema, lung abscess, bronchopleural fistula, pneumonia

  • heart (less common): CHD with R-L shunt (in children >60%), AVM, bacterial endocarditis

  • osteomyelitis

• Penetrating trauma or surgery

• Cryptogenic (25%)

Predisposed:	diabetes mellitus, patients on steroids / immunosuppressive drugs, congenital / acquired immunologic deficiency
Organism:	anaerobic streptococcus (most common), bacteroides, staphylococcus; in 20% multiple organisms; in 25% sterile contents

Pathophysiology:

Stage I:	vascular congestion, petechial hemorrhage, edema
Stage II:	cerebral softening + necrosis
Stage III:	(after 2 3 weeks) liquefaction, cavitation + capsule consisting of inner layer of granulation tissue, a middle collagenous layer and an outer astroglial layer; edema outside abscess capsule

• headache, drowsiness, confusion, seizure

• focal neurologic deficit

• fever, leukocytosis (resolves with encapsulation)

Location:

typically at corticomedullary junction; frontal + temporal lobes; supratentorial: infratentorial = 2:1

NCCT:

• zone of low density with mass effect (92%)

• slightly increased rim density (4%), development of collagen layer takes 10 14 days

• gas within lesion (4%) is diagnostic of gas-forming organism

CECT:

• ring enhancement (90%) with peripheral zone of edema

• homogeneous enhancement in lesions <0.5 cm

• edema + contrast enhancement suppressed by steroids

• smooth regular 1 3-mm thick wall with relative thinning of medial wall (secondary to poorer blood supply of white matter)

• multiloculation + subjacent daughter abscess in white matter

MR:

(most sensitive modality)

• centrally increased / variable intensity with hypointense rim on T2WI

• outside border of increased signal intensity on T2WI (edema)

• restricted diffusion in abscess core (CHARACTERISTIC)

Cx:

1. (1) Development of daughter abscesses toward white matter
2. (2) Rupture into ventricular system / subarachnoid space (thinner abscess capsule formation on medial wall of abscess related to fewer blood vessels) producing ventriculitis meningitis

Dx helpful features:

• multiple lesions at gray-white matter border

• clinical history of altered immune status

• R-to-L shunt: eg, pulmonary AV fistula

• foreign travel

• high-risk behavior: eg, IV drug abuse

DDx:

primary / metastatic neoplasm, subacute infarction, resolving hematoma

Granulomatous Abscess

• Tuberculoma

• Sarcoid abscess

• Fungal abscess: coccidioidomycosis, mucormycosis (in diabetics), aspergillosis, cryptococcus

Predisposed:

immunocompromised host

• enhancement of leptomeningeal surface

• nodular / ring-enhancing parenchymal lesion

Cx:

Communicating hydrocephalus (secondary to thick exudate blocking basal cisterns)

Acrania

• = exencephaly

• = developmental anomaly characterized by partial / complete absence of membranous neurocranium + complete but abnormal development of brain tissue

Incidence:	25 cases reported
Cause:	impaired migration of mesenchyme to its normal location under the calvarial ectoderm resulting in failure for development of dura mater + skull + musculature
Time:	develops after closure of anterior neuropore during 4th week

May be associated with:

• cleft lip, bilateral absence of orbital floors, metatarsus

• varus, talipes, cervicothoracic spina bifida

• elevation of maternal serum AFP

• absence of calvarium

• normal ossification of chondrocranium (face, skull base)

• hemispheres surrounded by thin membrane

Prognosis:	uniformly lethal; progression to anencephaly (brain destruction secondary to exposure to amniotic fluid + mechanical trauma)
DDx:	encephalocele, anencephaly, osteogenesis imperfecta, hypophosphatasia

Adrenoleukodystrophy

• = BRONZED SCLEROSING ENCEPHALOMYELITIS

• = inherited metabolic disorder characterized by progressive demyelination of cerebral white matter + adrenal insufficiency

P.264

Etiology:	defective peroxisomal fatty acid oxidation due to impaired function of lignoceryl-coenzyme A ligase with accumulation of saturated very long chain fatty acids (cholesterol esters) in white matter + adrenal cortex + testes
Dx:	assay of plasma, red cells, cultured skin fibroblasts for the presence of increased amounts of very long chain fatty acids

Mode of inheritance:

• X-linked recessive in boys (common)

• autosomal recessive in neonates (uncommon)

Histo:	PAS cytoplasmic inclusions in brain, adrenals, other tissues
Age:	3 10 years (X-linked recessive)

• ataxia

• deteriorating vision (27%), loss of hearing (50%)

• optic disk pallor

• adrenal gland insufficiency (abnormal increased pigmentation, elevated ACTH levels)

• altered behavior, attention disorder, mental deterioration, death

Location:

disease process usually starts in central occipital white matter, advances anteriorly through internal + external capsules + centrum semiovale, centripetal progression to involve subcortical white matter, interhemispheric spread via corpus callosum particularly splenium, involvement of optic radiation auditory system pyramidal tract

CT:

• large symmetric low-density lesions in occipitoparietotemporal white matter (80%) advancing toward frontal lobes + cerebellum

• thin curvilinear / serrated enhancing rims near edges of lesion

• initial frontal lobe involvement (12%)

• calcifications within hypodense areas (7%)

• cerebral atrophy in late stage (progressive loss of cortical neurons)

MR:

• hypointensity on T1WI in affected areas (hypointense atrophic splenium of corpus callosum)

• hyperintense bilateral confluent areas on T2WI

Prognosis:

usually fatal within several years after onset of symptoms

Adrenomyeloneuropathy

• = clinically milder form with later age of onset

• symptoms of spinal cord demyelination + peripheral neuropathy

Agenesis of Corpus Callosum

• = COMPLETE DYSGENESIS OF CORPUS CALLOSUM

• = failure of formation of corpus callosum originating from the lamina terminalis at 7 13 weeks from where a phalanx of callosal tissue extends backward arching over the diencephalon; usually developed by 20 weeks

Incidence:	0.7 5.3%
Cause:	congenital, acquired (infarction of ACA)
Histo:	axons from cerebral hemispheres that would normally cross continue along medial walls of lateral ventricles as longitudinal callosal bundles of Probst that terminate randomly in occipital + temporal lobes

Associated with:

• CNS anomalies (85%):

  • Dandy-Walker cyst (11%)

  • Interhemispheric arachnoid cyst may be continuous with 3rd and lateral ventricles

  • Hydrocephalus (30%)

  • Midline intracerebral lipoma of corpus callosum often surrounded with ring of calcium (10%)

  • Arnold-Chiari II malformation (7%)

  • Midline encephalocele

  • Porencephaly

  • Holoprosencephaly

  • Hypertelorism median cleft syndrome

  • Polymicrogyria, gray-matter heterotopia

• Cardiovascular, gastrointestinal, genitourinary anomalies (62%)

• Abnormal karyotype (trisomy 13, 15, 18)

• normal brain function in isolated agenesis

• intellectual impairment; seizures

• absence of septum pellucidum + corpus callosum + cavum septi pellucidi

• longitudinal bundles of Probst create crescentic lateral ventricles:

  • colpocephaly (= dilatation of trigones + occipital horns + posterior temporal horns in the absence of splenium

  • bat-wing appearance of lateral ventricles (= wide separation of lateral ventricles with straight parallel parasagittal orientation with absent callosal body)

  • laterally convex frontal horns in case of absent genu of corpus callosum

• high-riding third ventricle = upward displacement of widened 3rd ventricle often to level of bodies of lateral ventricle

• anterior interhemispheric fissure adjoins elevated 3rd ventricle communication (PATHOGNOMONIC)

• interhemispheric cyst = interhemispheric CSF collection as an upward extension of 3rd ventricle

• enlarged foramina of Monro

• sunburst gyral pattern = dysgenesis of cingulate gyrus with characteristic radial orientation of cerebral sulci from the roof of the 3rd ventricle (on sagittal images)

• failure of normal convergence of calcarine + parieto-occipital sulci

• persistent eversion of cingulate gyrus (rotated inferiorly + laterally) with absence on midsagittal images

• incomplete formation of Ammon's horn in the hippocampus

OB-US (>22 weeks GA):

• absence of septum pellucidum

• teardrop ventriculomegaly = disproportionate enlargement of occipital horns = colpocephaly

• dilated + elevated 3rd ventricle

• radial array pattern of medial cerebral sulci

Angio:

• wandering straight posterior course of pericallosal arteries (lateral view)

• wide separation of pericallosal arteries secondary to intervening 3rd ventricle (anterior view)

• separation of internal cerebral veins

• loss of U-shape in vein of Galen

P.265

DDx:

1. (1) Prominent cavum septi pellucidi + cavum vergae (should not be mistaken for 3rd ventricle)
2. (2) Arachnoid cyst in midline (suprasellar, collicular plate) raising and deforming the 3rd ventricle and causing hydrocephalus

Partial Agenesis of Corpus Callosum

• = milder form of callosal dysgenesis (best seen on MR) depending on time of arrested growth (anteroposterior development of genu + body + splenium, however, rostrum forming last)

  • genu only

  • genu + part of the body

  • genu + entire body

  • genu + body + splenium (without rostrum)

Aids

• = DNA retrovirus infection attacking monocytes + macrophages, which leads to deficient cell-mediated immunity

Incidence:	1% of population in United States is HIV-seropositive; 187,000 new cases in 1991
Histo:	formation of microglial nodules instead of granulomas in 75 80% of autopsied brains

• neurologic symptoms as initial complaint in 7 10%, ultimately afflict up to 40 60%: personality + mental status changes, headache, memory loss, difficulty to concentrate, depression, confusion, dementia, new onset of seizures, focal deficit from mass lesion

• Any male with neurologic symptoms between age 20 and 50 has AIDS until proven otherwise

• Unusual presentations are clues to HIV infection: pansinusitis, mastoiditis, parotid cysts, cervical adenopathy, hypointense spine

• ATROPHY:

  • Malnutrition, dehydration, steroid therapy, chronic dialysis, normal aging

  • AIDS dementia complex (ADC)

  • = Subacute encephalitis = HIV encephalitis

  • = cognitive disturbances that progress to dementia

    Etiology:	HIV-1 infection of CNS macrophages generating neurotoxic factors
    Prevalence:	7 27% of AIDS patients
    Histo:	predominantly perivascular HIV encephalitis; HIV leukoencephalopathy characterized by diffuse myelin loss + infiltration by macrophages

  • cerebral atrophy

  • subtly increased signal intensities on T2 and FLAIR sequences without mass effect (from leaky capillaries with egress of water):

    • focal / diffuse

    • symmetric / asymmetric

    • reversible / nonreversible

  • INTRA-AXIAL LESION WITHOUT MASS EFFECT

    • Progressive multifocal leukoencephalopathy (PML)

      Prevalence:	4% of AIDS patients
      Etiology:	reactivation of ubiquitous JC papovavirus
      Histo:	lysis of oligodendrocytes resulting in demyelination

  • altered mental status

  • speech, motor and visual disturbances

  Location:

  frontoparietal > temporo-occipital cerebral hemispheres; white matter tracts in cerebellum, brainstem, deep gray matter

  • bilateral white matter lesions (92%); confluent (94%); discrete (67%) in periventricular region + centrum semiovale + subcortical white matter

  • gray matter lesions in thalamus + basal ganglia (from involvement of traversing white matter tracts)

  • mild cortical atrophy (up to 69%)

  • ventricular dilatation (50%)

  CT:

  • single / multiple hypoattenuating white matter lesions without edema / mass effect

  MR:

  • hypointense lesions on T1WI

  • hyperintense lesions on T2 and FLAIR images

  • no enhancement

  Prognosis:

  death within 2 5 months

• MASS LESION

  • With multiple CNS lesions toxoplasmic encephalitis is the more likely diagnosis!

  • With a single CNS lesion the probability of lymphoma is at least equal to toxoplasmosis!

    • Toxoplasmosis

      • Most common cerebral mass lesion in AIDS!

      • 2 3 times more frequent than lymphoma!

        Organism:	Toxoplasma gondii; reservoirs in feces of house cat + uncooked meat (eg, pork, free-range chicken)
        Spread:	hematogenous
        Incidence:	3 40% of AIDS patients; 20 70% of normal adult population is seropositive for antibodies

    CT:

    • multiple small <2-cm hypoattenuating masses with ring enhancement

    MR:

    • restricted diffusion similar to an abscess

    Rx:	empiric therapy (pyrimethamine + sulfadiazine for 3 weeks)
    Dx:	biopsy

  • Primary CNS lymphoma (PCNSL)

    • = high-grade B-cell NHL with strong association with Epstein-Barr virus infection

    Prevalence:

    2 10%

    • Initial manifestation in 0.6% of AIDS patients

    • Second most common cause of a CNS mass in AIDS patients

    Location:

    anywhere; mostly periventricular; may encase ventricles by subependymal spread (= rim-lymphoma); crosses corpus callosum (DDx: edema from infection will not)

    • uni- or multifocal lesions + variable mass effect

    • doubling in size within 2 weeks

    • paucity of edema

    NECT:

    • often increased attenuation (because of high nuclear-to-cytoplasmic ratio)

    P.266

    
    

    MR:

    • iso- to hypointense on T1WI

    • variable intensity on T2 / FLAIR; may be hypointense (due to high cell density)

    • homogeneous enhancement; frequent ring enhancement in AIDS patients (due to central necrosis)

      • Steroids may inhibit contrast enhancement

    Tl-201 SPECT (100% sensitive, 93% specific):

    • uptake (DDx: toxoplasmosis not avid)

    Dx:	brain biopsy for unifocal lesion
    Rx:	sensitive to radiation therapy

  • Fungal, granulomatous, viral, bacterial infection

    • Cryptococcosis

      • = common soil fungus infecting lungs followed by hematogenous spread

      • Most common cause of fungal infection in AIDS patients

        Path:	choroid plexitis, meningitis, encephalitis (lack of anticryptococcal factors in CSF)
        Incidence:	5% of all patients with AIDS

      • headache, malaise, fever, nausea, vomiting

        Location:

        extension along Virchow-Robin spaces

    • hydrocephalus + cortical / central atrophy (with inadequate immune response)

    • enhancing granulomatous meningitis (with sufficient immune response)

    CT:

    • frequently normal

    • pseudocystic perivascular lesions in region of basal ganglia

    MR:

    • low T1 + high T2 signal intensities without enhancement in lenticulostriate region (= gelatinous pseudocyst)

    • leptomeningeal enhancement

    Dx:	detection of cryptococcal antigen in CSF
    Prognosis:	mean survival of 2 3 months

  • Other opportunistic CNS infections:

    • tuberculosis, neurosyphilis

    Rx:

    azidothymidine (AZT)

Alexander Disease

• = FIBRINOID LEUKODYSTROPHY

Age:

as early as first few weeks of life

• macrocephaly

• failure to attain developmental milestones

• progressive spastic quadriparesis

• intellectual failure

Location:

frontal white matter gradually extending posteriorly into parietal region + internal capsule

CT:

• low-density white matter lesion

• contrast enhancement near tip of frontal horn

MR:

• prolonged T1 + T2 relaxation times

Prognosis:

death in infancy / early childhood

Alzheimer Disease

• = diffuse gray matter disease with large loss of cells from cerebral cortex + other areas

• Most common of dementing disorders in elderly!

Incidence:

10% of people >65 years of age; 50% of people >85 years of age

• slowly progressing memory loss, dementia (large overlap with other dementias of elderly)

• cracked walnut appearance = symmetrically enlarged sulci in high-convexity area

• focal atrophic change in medial temporal lobe (82% sensitive, 75% specific, 80% accurate):

  • volume loss of hippocampus + parahippocampal gyrus

  • enlargement of perihippocampal fissures

• smooth periventricular halo of hyperintensity (50%)

Amyotrophic Lateral Sclerosis

• = most common form of motor neuron disease (without autonomic / sensory / cognitive involvement)

Cause:	free radical damage to neurons / autoimmune process / heavy metal toxicity
Age:	middle late adulthood; M > F
Path:	atrophy of precentral gyrus
Histo:	loss of pyramidal + Betz cells in motor cortex; loss of anterior horn cells in spinal cord; swelling of proximal axons of neuronal cells

• progressive neurodegenerative disorder

  • upper neuronal symptoms: hyperreflexia, spasticity

  • lower neuronal symptoms: fasciculation, atrophy

MR:

• hyperintense corticospinal tracts (corona radiata, corpus callosum, posterior limb of internal capsule, ventral aspect of brain stem, anterolateral column of spinal cord) on T2WI

• low signal intensity in motor cortex on T2WI (due to iron deposition)

DDx:

Friedreich ataxia, vitamin B₁₂ deficiency (abnormal signal limited to internal capsule)

Anencephaly

• = lethal anomaly with failure of closure of the rostral end of the neural tube by 5.6 weeks MA

• Associated with highest AF-AFP and MS-AFP values; >90% will be detected with MS-AFP 2.5 MoM

Incidence:	1:1,000 births (3.5:1,000 in South Wales); M:F = 1:4; most common congenital defect of CNS; 50% of all neural tube defects
Recurrence rate:	3 4%
Etiology:	multifactorial (genetic + environmental)
Path:	absence of cerebral hemispheres + cranial vault; partial / complete absence of diencephalic + mesencephalic structures; hypophysis + rhombencephalic structures usually preserved
Risk factors:	family history of neural tube defect; twin pregnancy

Associated anomalies:

• spinal dysraphism (17 50%), cleft lip / palate (2%), clubfoot (2%), umbilical hernia, amniotic band syndrome

• absence of bony calvarium cephalad to orbits

• cranial soft-tissue mass (= angiomatous stroma)

• bulging froglike eyes

P.267




• short neck

• polyhydramnios (40 50%) after 26 weeks GA (due to failure of normal fetal swallowing) / oligohydramnios

Dx:	in 100% >14 weeks GA
Prognosis:	uniformly fatal within hours to days of life; in 53% premature birth; in 68% stillbirth
DDx:	acrania, encephalocele, amniotic band syndrome

Aneurysm of CNS

Etiology:

• congenital (97%) = berry aneurysm in 2% of population (in 20% multiple); associated with aortic coarctation + adult polycystic kidney disease

• infectious (3%) = mycotic aneurysm

• arteriosclerotic: fusiform shape

• traumatic

• neoplastic

• fibromuscular disease

• collagen vascular disease

Risk factors:

• family history for aneurysms in 1st- / 2nd-degree relatives

• female gender

• age >50 years

• cigarette smoking

• oral contraceptives / pregnancy

• Marfan syndrome, pseudoxanthoma elasticum, Ehlers-Danlos syndrome, neurofibromatosis type 1

• polycystic kidney disease

• asymmetry of circle of Willis

• cerebral arteriovenous malformation

Pathogenesis:

arterial wall deficient in tunica media + external elastic lamina (natural occurrence with advancing age)

Location of aneurysm:

• by autopsy:

  • circle of Willis (85%):

    • aCom (25%), pCom (18%), MCA bifurcation (25%), distal ACA (5%), ICA at bifurcation (4%), ophthalmic a. (4%), anterior choroidal a. (4%)

  • posterior fossa (15%):

    • basilar bifurcation (7%), basilar trunk (3%), vertebral-PICA (3%), PCA (2%)

  • by angiography (= symptomatic aneurysms):

    • pCom (38%) > aCom (36%) > MCA bifurcation (21%) > ICA bifurcation > tip of basilar artery (2.8%)

  • by risk of bleeding: 1 2% per year

    • aCom (70% bleed), pCom (2nd highest risk)

    • Aneurysms at bifurcations / branching points are at greatest risk for rupture!

  • CECT:

    • detection rate of aneurysms at pCom (40%), aCom / MCA, basilar artery (80%)

Angio (all 4 cerebral vessels):

• contrast outpouching

• <2 mm infundibuli typically occur at pCom / anterior choroidal a. origin

• mass effect in thrombosed aneurysm

• 2nd arteriogram within 1 2 weeks detects aneurysm in 10 20% following negative 1st angiogram!

Prognosis:

• Death in 10% within 24 hours from concomitant intracerebral hemorrhage, extensive brain herniation, massive infarcts + hemorrhage within brainstem; 45% mortality within 30 days (25% prior to admission)

• Complete recovery in 58% of survivors

• Cerebral ischemia + infarction

• Rebleeding rate: 12 20% within 2 weeks, 11 22% within 30 days, up to 50% within 6 months (increased mortality); thereafter 1 2 4% risk/year

Cx:	subdural hematoma
Surgical mortality rate:	50% for ruptured, 1 3% for unruptured aneurysms

Cavernous Sinus Aneurysm

Age:	20 70 years, peak 5th 6th decade; F >> M
Cause:	sinus thrombophlebitis

• progressive visual impairment

• cavernous sinus syndrome: trigeminal nerve pain, oculomotor nerve paralysis

Site:

extradural portion of cavernous sinus ICA

• undercutting of anterior clinoid process

• erosion of lateral half of sella

• erosion of posterior clinoid process

• invasion of middle cranial fossa

• enlargement of superior orbital fissure

• erosion of tip of petrous pyramid

• rimlike calcification (33%)

• displacement of thin bony margins without sclerosis

Rx:

often inoperable; balloon embolization parent artery occlusion

Giant Aneurysm

• = aneurysm larger than 2.5 cm in diameter, usually presenting with intracranial mass effect

Incidence:	25% of all aneurysms
Age:	no age predilection; M:F = 2:1
Location:	(arise from arteries at the base of the brain)

• middle fossa: cavernous segment of ICA (43%), supraclinoid segment of ICA, terminal bifurcation of ICA, middle cerebral artery

• posterior fossa: at tip of basilar artery, AICA, vertebral artery

Skull film:

• predominantly peripheral curvilinear calcification (22%)

• bone erosion (44%)

• pressure changes on sella turcica (18%)

CECT:

• target sign = centrally opacified vessel lumen + ring of thrombus + enhanced fibrous outer wall

• simple ring-blush (75%) of fibrous outer wall with total thrombosis

• little / no surrounding edema

MR:

• mixed signal intensity (combination of subacute + chronic hemorrhage, calcification)

Cx:

subarachnoid hemorrhage in <30%

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Ruptured Berry Aneurysm

Incidence:	28,000 cases/year = 10 cases/10,000 people/year
Age:	50 60 years of age; M:F = 1:2
Rupture size:	5 15 mm

• worst headache of one's life

• neck stiffness, nausea, vomiting

• sudden loss of consciousness (in up to 45%)

• history of warning leak / sentinel hemorrhage hours to days earlier

Clues for which aneurysm is bleeding:

• the largest aneurysm (87%)

• anterior communicating artery (70%)

• contralateral side of all visualized aneurysms (60%), nonvisualization due to spasm

mnemonic:

BISH

• Biggest

• Irregular contour

• Spasm (adjacent)

• Hematoma location

Location of blood suggesting accurately in 70% the site of the ruptured aneurysm:

• according to location of subarachnoid hemorrhage:

  1.	Anterior chiasmatic cistern:	aCom
  2.	Septum pellucidum:	aCom
  3.	Interhemispheric fissure:	aCom
  4.	Intraventricular:	aCom, ICA, MCA
  5.	Sylvian fissure:	MCA, ICA, pCom
  6.	Anterior pericallosal cistern:	ACA, aCom
  7.	Prepontine cistern:	basilar a.
  8.	Foramen magnum:	PICA
  9.	Symmetric distribution in subarachnoid space:	ACA + basilar a.

• according to location of cerebral hematoma:

  1.	Inferomedial frontal lobe:	aCom
  2.	Temporal lobe:	MCA
  3.	Corpus callosum:	pericallosal a.

• intraventricular hemorrhage:

  • from aneurysms at aCom, MCA, pericallosal artery

CAVE:

blood may have entered in retrograde manner from subarachnoid location

Multiple CNS Aneurysms

Cause:	congenital in 20 30%, mycotic in 22%
mnemonic:	FECAL P

• Fibromuscular dysplasia

• Ehlers-Danlos syndrome

• Coarctation

• Arteriovenous malformation

• Lupus erythematosus

• Polycystic kidney disease (adult)

• 35% of patients with one MCA aneurysm have one on the contralateral side (= mirror image aneurysms)!

• Simultaneous aneurysm + AVM in 4 15%

Mycotic Aneurysm

• = 3% of all intracranial aneurysms, multiple in 20%

Source:	subacute bacterial endocarditis (65%), acute bacterial endocarditis (9%), meningitis (9%), septic thrombophlebitis (9%), myxoma
Location:	peripheral to first bifurcation of major vessel (64%); often located near surface of brain especially over convexities

• suprasellar cistern = circle of Willis

• inferolateral sylvian fissure = middle cerebral artery trifurcation

• genu of corpus callosum = origin of callosomarginal artery

• bottom of 3rd ventricle = pericallosal a.

NCCT:

• aneurysm rarely visualized; indirect evidence from focal hematoma secondary to rupture

• zone of increased density / calcification

• increased density in subarachnoid, intraventricular, intracerebral spaces (extravasated blood)

• focal / diffuse lucency of brain (edema / infarction / vasospasm)

CECT:

• intense homogeneous enhancement within round / oval mass contiguous to vessels

• incomplete opacification with mural thrombus

Cx:

develop recurrent bleeding more frequently than congenital aneurysms

Supraclinoid Carotid Aneurysm

• = 38% of intracranial aneurysms

Site:	(a) at origin of pCom (65%)
	(b) at bifurcation of internal carotid artery (23%)
	(c) at origin of ophthalmic artery (12%) medial to anterior clinoid process; most likely to become giant aneurysm
Presentation:	bitemporal hemianopia (extrinsic compression on chiasm)

• calcification is rare (frequent in atherosclerotic cavernous sinus aneurysm)

Aqueductal Stenosis

• = focal reduction in size of aqueduct at level of superior colliculi / intercollicular sulcus (normal range, 0.2 1.8 mm²)

Embryology:

• aqueduct develops about the 6th week of gestation + decreases in size until birth due to growth pressure from adjacent mesencephalic structures

Incidence:

0.5 1:1,000 births; most frequent cause of congenital hydrocephalus (20 43%); recurrence rate in siblings of 1 4.5%; M:F = 2:1

Etiology:

• postinflammatory (50%): secondary to perinatal infection (toxoplasmosis, CMV, syphilis, mumps, influenza virus) or intracranial hemorrhage = destruction of ependymal lining of aqueduct with adjacent marked fibrillary gliosis

• developmental: aqueductal forking (= marked branching of aqueduct into channels) / narrowing / transverse septum (X-linked recessive inheritance in 25% of males)

• neoplastic (extremely rare): pinealoma, meningioma, tectal astrocytoma (may be missed on routine CT scans, easily differentiated by MR)

May be associated with:

other congenital anomalies (16%): thumb deformities

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• enlargement of lateral + 3rd ventricles with normal-sized 4th ventricle (4th ventricle may be normal with communicating hydrocephalus)

Prognosis:

11 30% mortality

Arachnoid Cyst

• = CSF-containing intraarachnoid cyst without ventricular communication / brain maldevelopment

Incidence:

1% of all intracranial masses

Origin:

• congenital: arising from clefts / duplication / splitting of arachnoid membrane with expansion by CSF due to secretory activity of arachnoid cells = true arachnoid cyst

• acquired: following surgery / trauma / subarachnoid hemorrhage / infection in neonatal period / associated with extraaxial neoplasm = loculation of CSF surrounded by arachnoidal scarring with expansion by osmotic filtration / ball-valve mechanism = leptomeningeal cyst = secondary arachnoid cyst = acquired arachnoid cyst

Histo:	cyst filled with clear fluid, thin wall composed of cleaved arachnoid membrane lined by ependymal / meningothelial cells
Age:	presentation at any time during life

• often asymptomatic

• symptomatic due to mass effect, hydrocephalus, seizures, headaches, hemiparesis, intracranial hypertension, craniomegaly, developmental delay, visual loss, precocious puberty, bobble-head doll syndrome

Location:

(arise in CSF cisterns between brain + dura)

• floor of middle fossa near tip of temporal lobe (sylvian fissure) in 50%

• suprasellar / chiasmatic cistern (may produce endocrinopathy) in 10%

• posterior fossa (1/3): cerebellopontine angle (11%), quadrigeminal plate cistern (10%), in relationship to vermis (9%), prepontine / interpeduncular cistern (3%)

• interhemispheric fissure, cerebral convexity, anterior infratentorial midline

• forward bowing of anterior wall of cranial fossa + elevation of sphenoid ridge

• extraaxial unilocular thin-walled CSF-density cyst with well-defined smooth angular margins

• compression of subarachnoid space + subjacent brain (minimal mass effect)

• may erode inner table of calvarium

• NO enhancement (intrathecal contrast penetrates into cyst on delayed scans)

• NO calcifications

MR (best modality):

• well-circumscribed lesion with same uniform signal intensity as CSF mass effect

Cx:	(1) hydrocephalus (30 60%)
	(2) concurrent subdural / intracystic hemorrhage
Prognosis:	favorable if removed before onset of irreversible brain damage
Rx:	fenestration / cyst-peritoneal shunting

CT-DDx:

• epidermoid cyst, dermoid, subdural hygroma, infarction, porencephaly

US-DDx:

• choroid plexus cyst, porencephalic cyst (communicates with ventricle), cystic tumor (solid components), midline cyst associated with agenesis of corpus callosum, dorsal cyst associated with holoprosencephaly, Dandy-Walker cyst (extension of 4th ventricle, developmental delay), vein of Galen aneurysm

Arteriovenous Fistula

• = abnormal communication between artery + vein resulting in tremendous amount of flow due to high pressure gradient; leading to enlargement + elongation of draining veins

Cause:

• Vessel laceration (delay between trauma + clinical manifestation due to delayed lysis of hematoma surrounding arterial laceration)

• Angiodysplasia: fibromuscular disease, neurofibromatosis, Ehlers-Danlos syndrome

• Congenital fistula

• pulsatile mass + thrill / bruit

• neurologic symptoms / deficit (due to arterial steal)

Location:

• carotid-cavernous sinus fistula (most common)

• vertebral artery fistula

• external carotid fistula (rare)

Arteriovenous Malformation

• = congenital abnormality consisting of a nidus of abnormal dilated tortuous arteries + veins with racemose tangle of closely packed pathologic vessels resulting in shunting of blood from arterial to venous side without intermediary capillary bed

Prevalence:	0.1%; Most common type of symptomatic vascular malformation!
Histo:	affected arteries have thin walls (no elastica, small amount of muscularis); intervening gliotic brain parenchyma between vessels
Age:	80% by end of 4th decade; 20% <20 years of age; peak age 20 40 years
Associated with:	aneurysm in feeding artery in 10%

• headaches, seizures (nonfocal in 40%), mental deterioration

• progressive hemispheric neurologic deficit (50%)

• ictus from acute intracranial hemorrhage (50%): multicompartmental in 31%, subarachnoid in 30%, parenchymal in 23%, intraventricular in 16%

Location:

usually solitary (2% multiple)

• supratentorial (90%): parietal > frontal > temporal lobe > paraventricular > intraventricular region > occipital lobe

• infratentorial (10%)

Vascular supply:

• pial branches of ICA in 73% of supratentorial location, in 50% of posterior fossa location

• dural branches of ECA in 27% with infratentorial lesions

• mixed

• NO mass effect (due to replacement of normal brain tissue) unless complicated by hemorrhage + edema

• adjacent parenchymal atrophy (due to vascular steal + ischemia)

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Skull film:

• speckled / ringlike calcifications (15 30%)

• thinning / thickening of skull at contact area with AVM

• prominent vascular grooves on inner table of skull (dilated feeding arteries + draining veins) in 27%

NCCT:

• irregular lesion with large feeding arteries + draining veins

• mixed density (60%): dense large vessels + hemorrhage + calcifications

• isodense lesion (15%): may be recognizable by mass effect

• low density (15%): brain atrophy due to ischemia

• not visualized (10%)

CECT:

• serpiginous dense enhancement in 80% (tortuous dilated vessels)

• No enhancement in thrombosed AVM

• No avascular spaces within AVM

• lack of mass effect / edema (unless thrombosed / bleeding)

• rapid shunting

• thickened arachnoid covering

• adjacent atrophic brain

MR:

• flow void due to rapid arteriovenous shunting (imaging with GRASS gradient echo + long TR sequences)

• 3-D TOF demonstrates feeding arteries + nidus + draining veins

Pitfalls:

(1) signal void in tortuous vessels; (2) nonvisualization of draining veins resulting from spin saturation; (3) difficulty differentiating blood flow from blood clot

Angio:

• grossly dilated efferent + afferent vessels with a racemose tangle ( bag of worms )

• arteriovenous shunting into at least one early draining vein

• negative angiogram (compression by hematoma / thrombosis)

Cx:	(1) Hemorrhage (common): bleeding on venous side due to increased pressure / ruptured aneurysm (5%)
(2)	Infarction
Prognosis:	10% mortality; 30% morbidity; 2 3% yearly chance of bleeding increasing to 6% in year following 1st bleed + 25% in year following 2nd bleed

Wyburn-Mason Syndrome

• = telangiectasias of skin + retinal cirsoid aneurysm + AVM involving entire optic tract (optic nerve, thalamus, geniculate bodies, calcarine cortex);

May be associated with:

AVMs of posterior fossa, neck, mandible / maxilla presenting in childhood

Astrocytoma

Incidence:

70 75% of all primary intracranial tumors; most common brain tumor in children (40 50% of all primary pediatric intracranial neoplasms)

Location:

• cerebral hemisphere (lobar), thalamus, pons, midbrain, may spread across corpus callosum (incidence of occurrence proportional to amount of white matter); no particular lobar distribution;

  • in adults: central white matter of cerebrum (15 30% of all gliomas)

  • in children: cerebellum (40%) + brainstem (20%), supratentorial (30%)

Well-differentiated = Low-grade Astrocytoma

Incidence:	9% of all primary intracranial tumors;
	10 15% of gliomas
Age:	20 40 years; M > F
Path:	benign nonmetastasizing; poorly defined borders with infiltration of white matter + basal ganglia + cortex; NO significant tumor vascularity / necrosis / hemorrhage; blood-brain barrier may remain intact
Histo:	homogeneous relatively uniform appearance with proliferation of well-differentiated multipolar fibrillary / protoplasmic astrocytes; mild nuclear pleomorphism + mild hypercellularity; mitoses rare
Location:	posterior fossa in children, supratentorial in adults (typically lobar); distribution proportional to amount of white matter

• may develop a cyst with high-protein content (rare)

CT:

• usually hypodense lesion with minimal mass effect + minimal / NO peritumoral edema

• well-defined tumor margins

• central calcifications (15 20%)

• minimal / no contrast enhancement (normal capillary endothelial cells)

MR:

• well-defined hypointense lesion with little mass effect / vasogenic edema / heterogeneity on T1WI

• hyperintense on T2WI

• little / no enhancement on Gd-DTPA

• cyst with content hyperintense to CSF (protein content)

• hyperintense area within tumor mass (paramagnetic effect of methemoglobin)

• inhomogeneous gadolinium-DTPA enhancement of tumor nodule

Angio:

• majority avascular

Prognosis:

3 10 years postoperative survival; occasionally converting into more malignant form several years after presentation

Anaplastic Astrocytoma

Incidence:	11% of all primary intracranial neoplasms; 25% of gliomas
Path:	frequently vasogenic edema; NO necrosis / hemorrhage
Histo:	less well differentiated with greater degree of hypercellularity + pleomorphism, multipolar fibrillary / protoplasmic astrocytes; mitoses + vascular endothelial proliferation common
Location:	typically frontal + temporal lobes
Distribution:	proportional to amount of white matter

MR:

• moderate mass effect

• well-defined slightly heterogeneous hypointense lesion on T1WI with prevalent vasogenic edema

• hyperintense on T2WI

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• enhancement on Gd-DTPA

Prognosis:

2 years postoperative survival

Pilocytic Astrocytoma

• = JUVENILE PILOCYTIC ASTROCYTOMA

• = most benign histologic subtype of astrocytoma without progression to high-grade glioma

Incidence:	0.6 5.1% of all intracranial neoplasms Most common pediatric glioma; 85% of all cerebellar + 10% of all cerebral astrocytomas in children
Age:	predominantly in children + young adults; 75% in first 2 decades of life; peak age between birth and 9 years of age; M:F = 1:1
Histo:	biphasic pattern of compact bipolar pilocytic (hairlike) astrocytes arranged mostly around vessels + loosely aggregated protoplasmic astrocytes undergoing microcystic degeneration
Associated with:	neurofibromatosis type 1 (in 15 21% of NF1 patients as the most common tumor)

Location:

common:	cerebellum, hypothalamus (around 3rd ventricle), optic nerve / chiasm
less common:	cerebral hemispheres (adults), cerebral ventricles, velum interpositum, spinal cord
Site:	near ventricles (82%)

Imaging patterns:

• Cyst with intensely enhancing mural nodule (67%)

  • nonenhancing cyst wall (21%)

  • enhancing cyst wall (46%)

• Solid mass (33%)

  • central nonenhancing necrotic zone (16%)

  • minimal / no cystic component (17%)

CT:

• well-demarcated smoothly marginated round / oval mass with cystic features

• occasional calcifications

• intense enhancement (94%)

• multilobulated / dumbbell appearance along optic pathway

• mural tumor nodule located in wall of cerebellar cyst

MR:

• isointense to normal brain on T1WI + hyperintense on T2WI

  WHO Classification of Astrocytomas

  Grade I	Circumscribed astrocytoma	generally benign well-circumscribed tumor, specific unique histologic features for each tumor, pilocytic astrocytoma (most common), subependymal giant cell astrocytoma; no tendency to progress to higher grade; low rate of recurrence
  Grade II	Astrocytoma	diffusely infiltrating; well-differentiated; minimal pleomorphism or nuclear atypia; no vascular proliferation / necrosis
  Grade III	Anaplastic astrocytoma	pleomorphism and nuclear atypia; increased cellularity; mitotic activity; vascular proliferation + necrosis absent
  Grade IV	Glioblastoma multiforme	marked vascular proliferation and necrosis; increased cellularity; anaplasia + pleomorphism; variable mitotic activity; cell type may be poorly differentiated, fusiform, round or multinucleated

• small rim of vasogenic edema (low biologic activity)

• increased heterogeneous signal intensity on early Gd-DTPA-enhanced T1WI; homogeneous enhancement on delayed images

Prognosis:	relatively benign clinical course, almost never recurs after surgical excision; 94% + 79% postsurgical 10-year + 20-year survival; NO malignant transformation to anaplastic form
DDx:	metastasis, hemangioblastoma, atypical medulloblastoma

Cerebellar Pilocytic Astrocytoma

• headache, vomiting, gait disturbance

• blurred vision, diplopia, neck pain

• hydrocephalus, truncal ataxia, appendicular dysmetria

• papilledema, 6th nerve palsy, nystagmus

Location:

cerebellar hemisphere (29 53%), brainstem (34%), vermis (16 71%),

Brainstem Pilocytic Astrocytoma

• nausea, vomiting, ataxia, torticollis

• papilledema, nystagmus, 6th & 7th nerve palsy exophytic extension from dorsal surface obliteration of 4th ventricle

DDx:

fibrillary astrocytoma (dismal prognosis)

Hypothalamic Pilocytic Astrocytoma

• obesity, diabetes insipidus

• diencephalic syndrome (= emaciation despite normal / slightly decreased caloric intake, alert appearance, hyperkinesis, irritability, normal / accelerated growth)

• hemiparesis (compression of corticospinal tracts) hydrocephalus

Prognosis:

may regress spontaneously

Cerebral Pilocytic Astrocytoma

• headache, seizure activity, hemiparesis, ataxia, nausea, vomiting

Location:

temporal lobe

Optic Pathway Pilocytic Astrocytoma

Pleomorphic Xanthoastrocytoma

• = superficially located supratentorial tumor that involves leptomeninges

Prevalence:	1% of all brain neoplasms
Age:	average age of 26 years (range, 5 82 years)
Path:	circumscribed tumor attached to meninges with infiltration into surrounding brain
Histo:	pleomorphic spindled tumor cells (reactive to glial fibrillary acidic protein) with intracytoplasmic lipid (xanthomatous) deposits in a dense intercellular reticulin network; giant cells; eosinophilic granular bodies; WHO grade II tumor

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• long history of seizures (71%)

Location:	supratentorial (98%): temporal (49%) / parietal (17%) / frontal (10%) / occipital (7%) lobe; thalamus; cerebellum; spinal cord
	Its peripheral location is the single most consistent imaging feature

• cystic (48%) supratentorial mass with mural nodule

• intense enhancement of solid portions

• CHARACTERISTIC involvement of leptomeninges (71%)

• peritumoral vasogenic edema / calcification / skull erosion are uncommon

CT:

• hypo- / isoattenuating mass

MR:

• hypo- to isointense relative to gray matter on T1WI

• hyper- to isointense on T2WI

Rx:	surgical resection (unresponsive to chemotherapy + radiation therapy)
Prognosis:	81% 5-year survival rate; 70% 10-year survival rate; high rate of recurrence; malignant transformation in 20%
DDx:	meningioma, glioblastoma multiforme, oligodendroglioma, metastatic disease, infection

Ataxia-Telangiectasia

• = autosomal recessive disorder characterized by telangiectasias of skin + eye, cerebellar ataxia, sinus + pulmonary infections, immunodeficiencies, propensity to develop malignancies

Incidence:	1:40,000 livebirths
Path:	neuronal degradation + atrophy of cerebellar cortex (? from vascular anomalies)

• cerebellar ataxia at beginning of walking age

• progressive neurologic deterioration

• oculomotor abnormalities, dysarthric speech, choreoathetosis, myoclonic jerks

• mucocutaneous telangiectasias: bulbar conjunctiva, ears, face, neck, palate, dorsum of hands, antecubital + popliteal fossa

• recurrent bacterial + viral sinopulmonary infections

• cerebellar cortical atrophy: diminished cerebellar size, dilatation of 4th ventricle, increased cerebellar sulcal prominence

• cerebral hemorrhage (rupture of telangiectatic vessels)

• cerebral infarct (emboli shunted through vascular malformations in lung)

Cx:	(1) Bronchiectasis + pulmonary failure (most common cause of death)
	(2) Malignancies (10 15%): lymphoma, leukemia, epithelial malignancies

Benign Macrocephaly of Infancy

• = Benign enlargement of subarachnoid spaces = Benign extraaxial collections of infancy = external hydrocephalus

Cause:	defective reabsorption of CSF at arachnoid villi; commonly familial with autosomal dominant inheritance
Age:	presentation between 3 and 12 months

• infant with macrocephaly (= head circumference >90th percentile)

• delayed motor development, hypotonia (in up to 30%)

Location:

bilateral frontoparietal area + interhemispheric fissure + sylvian fissure + basal cisterns

• enlarged subarachnoid spaces

• floating cortical veins

• NO / mild ventricular enlargement

Cx:	subdural hematoma in response to minor impacts
Prognosis:	self-limiting transient development that usually resolves by 2 3 years
DDx:	(1) Cerebral atrophy (diffuse sulcal prominence not localized to frontoparietal area)
	(2)	Spontaneous subdural hematoma (12%)

Binswanger Disease

• = encephalopathia subcorticalis progressiva= leukoariaosis = SUBCORTICAL ARTERIOSCLEROTIC ENCEPHALOPATHY (SAE)

Cause:	arteriosclerosis affecting the poorly collateralized distal penetrating arteries (perforating medullary arteries, thalamoperforators, lenticulostriates, pontine perforators); positive correlation with hypertension + aging
Path:	ischemic demyelination / infarction
Age:	>60 years

• psychiatric changes, intellectual impairment, slowly progressive dementia, transient neurologic deficits, seizures, spasticity, syncope

Location:

periventricular white matter, centrum semiovale, basal ganglia; subcortical white matter U fibers + corpus callosum are spared

• multifocal hypodense lesions (periventricular, centrum semiovale) with sparing of U fibers

• lacunar infarcts in basal ganglia

• sulcal enlargement + dilated lateral ventricles (brain atrophy)

MR:

• focal areas of increased signal intensity on T2WI (= unidentified bright objects )

DDx:

leukodystrophy, progressive multifocal leukoencephalopathy, multiple sclerosis

Canavan Disease

• = SPONGIFORM LEUKODYSTROPHY

• = rare form of leukodystrophy as an autosomal recessive disorder, most common in Ashkenazi Jews

Incidence:	<100 reported cases
Cause:	deficiency of aspartoacyclase leading to accumulation of N-acetylaspartic acid in brain, plasma, urine, CSF
Histo:	spongy degeneration of white matter with astrocytic swelling + mitochondrial elongation
Age:	3 6 months

• marked hypotonia

• progressive megalencephaly

• seizures

• failure to attain motor milestones

• spasticity

• intellectual failure

• optic atrophy with blindness

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• swallowing impairment

• diffuse symmetric white matter abnormality

• may involve basal ganglia

• cortical atrophy

CT:

• low-density white matter

MR:

• white matter hypointense on T1WI + hyperintense on T2WI

Prognosis:	death in 2nd 5th year of life
Dx:	(1) elevation of N-acetylaspartic acid in urine
	(2) deficiency of aspartoacyclase in cultured skin fibroblasts

Capillary Telangiectasia

• = CAPILLARY ANGIOMA

• = nest of dilated capillaries separated by normal neural tissue; commonly cryptic

May be associated with:

• hereditary Rendu-Osler-Weber syndrome, ataxia-telangiectasia syndrome, irradiation (latency period of 5 months to 22 years)

Age:

typically in elderly

• usually asymptomatic (incidental finding at necropsy)

Location:

mostly in pons / midbrain > cerebral cortex > spinal cord; usually multiple / may be solitary

• poorly defined area of dilated vessels (resembling petechiae)

• best delineated with MR (due to hemorrhage) with focus of increased signal intensity on contrast-enhanced studies

Cx:	punctate hemorrhage (uncommon), gliosis + calcifications (rare)
Prognosis:	bleeding in pons usually fatal
DDx:	cavernous angioma (identical on images)

Cavernous angioma of brain

• = Cavernous Hemangioma = cavernoma

Path:	well-circumscribed nodule of honeycomblike dilated endothelial lined spaces separated by fibrous collagenous bands without intervening neural tissue
Age:	3rd 6th decade; M > F

• seizures (commonly presenting symptom)

Location:

cerebrum (mainly subcortical) > pons > cerebellum; solitary > multiple

• NO obvious mass effect / edema

• usually contain blood degradation products of different stages

• slow blood flow in vascular channels

NCCT:

• extensive calcifications = hemangioma calcificans (20%)

• small round hyperdense region (CLUE)

• minimal surrounding edema

CECT:

• minimal / intense enhancement

• low-attenuation areas due to thrombosed portions

MR:

• typically popcorn appearance with bright lobulated center on T1WI + T2WI

• well-defined area of mixed signal intensity centrally (= mulberry -shaped lesion) with a mixture of increased signal intensity (= extracellular methemoglobin / slow blood flow / thrombosis)

• decreased intensity (= deoxyhemoglobin / intracellular methemoglobin / hemosiderin / calcification)

• surrounded by hypointense rim (= hemosiderin) on T2WI

Angio:

• negative = cryptic / occult vascular malformation

Cx:	hemorrhage of varying ages
DDx:	(1) Hemorrhagic neoplasm (edema, mass effect)
	(2) Small AVM (thrombosed / small feeding vessels, associated hemorrhage)
	(3) Capillary angioma (no difference)

Central Pontine Myelinolysis

• = OSMOTIC MYELINOLYSIS = OSMOTIC DEMYELINATION SYNDROME

Etiology:

• unknown; osmotic insult + metabolic compromise: comatose patient receiving rapid correction / overcorrection of severe hyponatremia >12 mmol/L/day (following prolonged IV fluid administration; 60 70% in chronic alcoholics)

Pathophysiology:

• rapid correction of sodium releases myelinotoxic compounds by gray matter components resulting in destruction of myelin sheaths (osmotic myelinolysis) with preservation of neurons + axons

• spastic quadriparesis + pseudobulbar palsy

• acute mental status change

• progression to pseudocoma (locked-in syndrome) in 3 5 days

Location:	(a) isolated pons lesion (most commonly)
	(b)	combined type: central + extrapontine areas: basal ganglia, cerebellar white matter, thalamus, caudate nucleus, subcortical cerebral white matter, corona radiata, lateral geniculate body

CT:

• diminished attenuation in central region of pons

MR (positive 1 2 weeks post-onset of symptoms):

• single central symmetric midline pons lesion:

  • trident-shaped / round (coronal scan) + bat-wing configuration (sagittal scan)

  • hypointense on T1WI + hyperintense on T2WI

• bilateral symmetric well-demarcated lesions in basal ganglia other extrapontine sites

Prognosis:	5 10% survival rate beyond 6 months
DDx:	hypoxia, Leigh disease, Wilson disease

Cephalocele

• = mesodermal defect in skull + dura with extracranial extension of intracranial structures with persistent connection to subarachnoid space

CRANIAL MENINGOCELE	= herniation of meninges + CSF only
ENCEPHALOCELE	= herniation of meninges + CSF + neural tissue

Nomenclature:

• based on origin of their roof + floor, eg frontonasal: frontal bone = roof, nasal bone = floor

Prevalence:

• 1 4 per 10,000 livebirths; 5 6 20% of all craniospinal malformations; predominant neural axis anomaly in fetuses spontaneously aborted <20 weeks GA; 3% of fetal anomalies detected with MS-AFP screening; 6% of all detected neural tube defects in fetuses

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Cause:

• failure of surface ectoderm to separate from neuroectoderm early in embryonic development

• @ Skull base

  • faulty closure of neural tube (without mesenchyme membranous cranial bone cannot develop)

  • failure of basilar ossification centers to unite

• @ Calvarium

  • defective induction of bone

  • pressure erosion of bone by intracranial mass / cyst

In 60% associated with:

• Spina bifida (7 30%)

• Corpus callosum dys- / agenesis

• Chiari malformation

• Dandy-Walker malformation

• Cerebellar hypoplasia

• Amniotic band syndrome: multiple irregular asymmetric off-midline encephaloceles

• Migrational abnormalities

• Chromosomal anomalies in 44% (trisomy 18)

• MS-AFP elevated in 3% (skin-covered in 60%)

• CSF rhinorrhea

• meningitis

Prognosis:	dependent on associated malformations + size and content of lesion; 21% liveborn; 50% survival in liveborns, 74% retarded
	Outcome poorer the larger the brain volume
Risk of recurrence:	3% (25% with Meckel syndrome)
DDx:	teratoma, cystic hygroma, iniencephaly, scalp edema, hemangioma, branchial cleft cyst, cloverleaf skull

Occipital Encephalocele (75%)

• Most common encephalocele in Western Hemisphere

Associated with:

• Meckel-Gruber syndrome

  • = occipital encephalocele + microcephaly + cystic dysplastic kidneys + polydactyly

• Dandy-Walker malformation

• Chiari malformation

• external occipital mass

Location:

supra- and infratentorial structures involved with equal frequency

• skull defect (visualized in 80%)

• flattening of basiocciput

• ventriculomegaly

• lemon sign = inward depression of frontal bones (33%)

• cyst-within-a-cyst (ventriculocele = herniation of 4th ventricle into cephalocele)

• acute angle between mass + skin line of neck and occiput

DDx:

cystic hygroma

Sincipital Encephalocele (13 15%)

• Most common variety in Southeast Asia!

Location:	midface about dorsum of nose, orbits, and forehead
Cause:	failure of anterior neuropore located near optic recess to close normally at 4th week GA

Types:

• Frontonasal (40 60%)

  • = herniation of dura mater through foramen cecum + fonticulus frontalis

• Nasoethmoidal (30%)

  • = persistent herniation of dural diverticulum through foramen cecum into prenasal space

• Combination of both (10%)

Associated with:

midline craniofacial dysraphism (dysgenesis of corpus callosum, interhemispheric lipoma, anomalies of neural migration, facial cleft, schizencephaly)

• obvious mass, broad nasal root, hypertelorism

• nasal stuffiness, rhinorrhea

• change in size during crying / Valsalva maneuver

• positive F rstenberg test = change in size during jugular compression

• soft-tissue mass extending to glabella / nasal cavity

• pedunculated intranasal mass extending from superomedial nasal cavity downward

• enlarged foramen cecum

OB-US:

• widened interorbital distance

CT:

• bifid / absent crista galli

• absent cribriform plate / frontal bone

MR:

• isointense relative to gray matter

• may be hyperintense on T2WI (due to gliosis)

N.B.:	biopsy is CONTRAINDICATED (due to potential for CSF leaks, seizures, meningitis)
Risk of recurrence:	6% of congenital CNS abnormalities for younger siblings
Rx:	complete surgical resection with repair of dura mater (NO neurologic deficit due to abnormal function of herniated brain)
DDx:	(1) Dacryocystocele / nasolacrimal mucocele
	(2) Nasal glioma (no subarachnoid connection on cisternography)

Sphenoidal Encephalocele (10%)

• = BASAL ENCEPHALOCELE

Age:

present at end of first decade of life

• clinically occult

• mass in nasal cavity, nasopharynx, mouth, posterior portion of orbit

• mouth breathing due to nasopharyngeal obstruction

• nasopharyngeal mass increasing with Valsalva

• diminished visual acuity with hypoplasia of optic discs

• hypothalamic-pituitary dysfunction

Associated with:

agenesis of corpus callosum (80%)

Types:

• sphenopharyngeal = through sphenoid body

• spheno-orbital = through superior orbital fissure

• sphenoethmoidal = through sphenoid + ethmoid

• transethmoidal = through cribriform plate

• sphenomaxillary = through maxillary sinus

Parietal Encephalocele (10 12%)

Associated with:

dysgenesis of corpus callosum, large interhemispheric cyst

• hole in sphenoid bone (seen on submentovertex film)

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• cranium bifidum = cranioschisis = split cranium (= skull defect) = smooth opening with well-defined sclerotic rim of cortical bone

• hydrocephalus in 15 80% (from associated aqueductal stenosis, Arnold-Chiari malformation, Dandy-Walker cyst)

• nonenhancing expansile homogeneous paracranial mass

• mantle of cerebral tissue often difficult to image in encephalocele (except with MR)

• intracranial communication often not visualized

• metrizamide / radionuclide ventriculography diagnostic

• microcephaly (20%)

• polyhydramnios

DDx:	(1) sonographic refraction artifact at skull edge
	(2) clover leaf skull (temporal bone may be partially absent)

Cerebellar Astrocytoma

• 2nd most frequent tumor of posterior fossa in children

Incidence:	10 20% of pediatric brain tumors
Histo:	mostly grade I
Age:	children > adults; no specific age peak; M:F = 1:1

Path:

• cystic lesion with tumor nodule ( mural nodule ) in cyst wall (50%); (midline astrocytomas cystic in 50%, hemispheric astrocytomas cystic in 80%)

• solid mass with cystic (= necrotic) center (40 45%)

• solid tumor without necrosis (<10%)

• cerebellar signs: truncal ataxia, dysdiadochokinesia

Location:

originating in midline with extension into cerebellar hemisphere (30%) > vermis > tonsils > brainstem

• calcifications (20%): dense / faint / reticular / punctate / globular; mostly in solid variety

• may develop extreme hydrocephalus (quite large when finally symptomatic)

CT:

• round / oval cyst with density of cyst fluid > CSF

• round / oval / plaquelike mural nodule with intense homogeneous enhancement

• cyst wall slightly hyperdense + nonenhancing (= compressed cerebellar tissue)

• uni- / multilocular cyst (= necrosis) with irregular enhancement of solid tumor portions

• round / oval lobulated fairly well-defined iso- / hypodense solid tumor with hetero- / homogeneous enhancement

MR:

• hypointense on T1WI + hyperintense on T2WI

• enhancement of solid tumor portion

Angio:

• avascular

Prognosis:

• malignant transformation exceedingly rare

  • 40% 25-year survival rate for solid cerebellar astrocytoma

  • 90% 25-year survival rate for cystic juvenile pilocytic astrocytoma

DDx of solid astrocytoma:

• Medulloblastoma (hyperdense mass, noncalcified)

• Ependymoma (fourth ventricle, 50% calcify)

DDx of cystic astrocytoma:

• Hemangioblastoma (lesion <5 cm)

• Arachnoid cyst

• Trapped 4th ventricle

• Megacisterna magna

• Dandy-Walker cyst

Cerebritis

• = focal area of inflammation within brain substance

CT:

• area of decreased density mass effect

• no contrast enhancement (initially) / central or patchy enhancement (later)

MR:

• focal area of increased intensity on T2WI

Cx:

brain abscess

Chiari Malformation

Chiari I Malformationx (adulthood)

• = cerebellar tonsillar ectopia

• = herniation of cerebellar tonsils below a line connecting basion with opisthion (= foramen magnum)

• Frequently isolated hindbrain abnormality of little consequence without supratentorial anomalies!

Proposed causes:

• small posterior fossa

• disproportionate CSF absorption from subarachnoid spinal space

• cerebellar overgrowth

Associated with:

• syringohydromyelia (20 30%)

• hydrocephalus (25 44%)

• malformation of skull base + cervical spine:

  • basilar impression (25%)

  • craniovertebral fusion, eg, occipitalization of C1 (10%), incomplete ossification of C1-ring (5%)

  • Klippel-Feil anomaly (10%)

  • platybasia

• NOT associated with myelomeningocele!

• benign cerebellar ectopia <3 mm of no clinical consequence; 3 5 mm of uncertain significance; >5 mm clinical symptoms likely

• no symptoms in childhood (unless associated with hydrocephalus / syringomyelia)

• may have cranial nerve dysfunction / dissociated anesthesia of lower extremities in adulthood

• downward displacement of cerebellar tonsils + medial part of the inferior lobes of the cerebellum 5 mm below the level of the foramen magnum

• inferior pointing peglike / triangular tonsils

• obliteration of cisterna magna

• elongation of 4th ventricle, which remains in normal position

• slight anterior angulation of lower brainstem

Chiari II Malformation (childhood)

• = ARNOLD-CHIARI MALFORMATION

• = most common and serious complex of anomalies secondary to a too small posterior fossa involving hindbrain, spine, mesoderm

• HALLMARK is dysgenesis of hindbrain with

  • caudally displaced 4th ventricle

  P.276

  
  

  • caudally displaced brainstem

  • tonsillar + vermian herniation through foramen magnum

Associated with:

• spinal anomalies

  • lumbar myelomeningocele (>95%)

  • syringohydromyelia

• supratentorial anomalies

  • dysgenesis of corpus callosum (80 85%)

  • obstructive hydrocephalus (50 98%) following closure of myelomeningocele

  • absence of septum pellucidum (40%)

  • excessive cortical gyration (stenogyria

    • = histologically normal cortex; polymicrogyria

    • = histologically abnormal cortex)

  • NOT associated with basilar impression / C1-assimilation / Klippel-Feil deformity!

• newborn: respiratory distress, apneic spells, bradycardia, impaired swallowing, poor gag reflex, retrocollis, spasticity of upper extremities

• teenager: gradual loss of function + spasticity of lower extremities

Skull film:

• L ckensch del (most prominent near torcular herophili / vertex) in 85% = dysplasia of membranous skull disappearing by 6 months of age

• scalloping of clivus + posterior aspect of petrous pyramids (from pressure of cerebellum) in 70 90% leading to shortening of IAC

• small posterior fossa

• enlarged foramen magnum + enlarged upper spinal canal secondary to molding in 75%

• absent / hypoplastic posterior arch of C1 (70%)

• @ Supratentorial

  • hydrocephalus (duct of Sylvius dysfunctional but probe patent); may not become evident until after repair of myelomeningocele (90%)

  • colpocephaly (= enlargement of occipital horns + atria) due to maldeveloped occipital lobes

  • hypoplasia / absence of splenium + rostrum of corpus callosum (80 90%)

  • bat-wing configuration of frontal horns on coronal views = frontal horns pointing inferiorly with blunt superolateral angle secondary to prominent impressions by enlarged caudate nucleus

  • hourglass ventricle = small biconcave 3rd ventricle secondary to large massa intermedia

  • interdigitation of medial cortical gyri (hypoplasia + fenestration of falx in up to 100%)

  • wide prepontine + supracerebellar cisterns

  • nonvisualization of aqueduct (in up to 70%)

  • stenogyria = multiple small closely spaced gyri at medial aspect of occipital lobe secondary to dysplasia (in up to 50%)

• @ Cerebellum

  • cerebellar peg = protrusion of vermis + hemispheres through foramen magnum (90%) resulting in craniocaudal elongation of cerebellum

  • hypoplastic poorly differentiated cerebellum (poor visualization of folia on sagittal images) secondary to severe degeneration

  • elongated / obliterated vertically oriented thin-tubed 4th ventricle with narrowed AP diameter exiting below foramen magnum (40%)

  • obliteration of CPA cistern + cisterna magna by cerebellum growing around brainstem

  • dysplastic tentorium with wide U-shaped incisura inserting close to foramen magnum (95%)

  • tectal beaking = fusion of midbrain colliculi into a single beak pointing posteriorly and invaginating into cerebellum

  • V-shaped widened quadrigeminal plate cistern (due to hypoplasia of cingulate gyri)

  • towering cerebellum = pseudomass = cerebellar extension above incisura of tentorium

  • triple peak configuration = corners of cerebellum wrapped around brainstem pointing anteriorly + laterally (on axial images)

  • flattened superior portion of cerebellum secondary to temporoparietal herniation

  • vertical orientation of shortened straight sinus

• @ Spinal cord

  • medulla + pons displaced into cervical canal

  • cervicomedullary kink = herniation of medulla posterior to spinal cord (up to 70%) at level of dentate ligaments

  • widened anterior subarachnoid space at level of brainstem + upper cervical spine (40%)

  • AP diameter of pons narrowed

  • upper cervical nerve roots ascend toward their exit foramina

  • syringohydromyelia

  • low-lying often tethered conus medullaris below L2

OB-US:

• hydrocephalus

• banana sign = cerebellum wrapped around posterior brainstem + obliteration of cisterna magna secondary to small posterior fossa + downward traction of spinal cord in Chiari II malformation

Chiari III Malformation

• most severe rare abnormality; probably unrelated to type I and II Chiari malformation

• low occipital / high cervical meningomyelo-encephalocele

Prognosis:

survival usually not beyond infancy

Chiari IV Malformation

• extremely rare anomaly probably erroneously included as type of Chiari malformation

• agenesis of cerebellum

• hypoplasia of pons

• small + funnel-shaped posterior fossa

Choroid Plexus Cyst

• = cyst arising from folding of neuroepithelium with trapping of secretory products + desquamated cells

Incidence:	0.9 3.6% in sonographic population;
	50% of autopsied brains
Histo:	no epithelial lining, filled with clear fluid debris

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May be associated with:

• aneuploidy (76% with trisomy 18, 17% with trisomy 21, 7% with triploidy / Klinefelter syndrome)

• In absence of other anomalies 1% of fetuses with choroid plexus cysts will have trisomy 18!

• In presence of other anomalies 4% of fetuses with choroid plexus cysts will have trisomy 18!

• 40 71% of autopsied fetuses with trisomy 18 have choroid plexus cysts bilaterally >10 mm in diameter

• Risk of chromosomal abnormality not linked to size, bilaterality, gestational age at appearance / disappearance

• usually asymptomatic

Location:	frequently at level of atrium; uni- / bilateral single / multiple round anechoic cysts 3 mm in size (average 4.5 mm, up to 25 mm)
Cx:	hydrocephalus (if cyst large)
Prognosis:	90% disappear by 28th week; may persist; in 95% of no significance

OB-management:

• a choroid plexus cyst should stimulate a thorough sonographic examination at >19 weeks; if no other sonographic abnormalities are identified, the yield of abnormal karyotype is low so that the risk of trisomy 18 (1:450 500) is lower than risk of fetal loss due to amniocentesis (approximately 1:200 300)

Risk of karyotype abnormality:

• 10 times with 1 additional defect

• 600 times with 2 additional defects

DDx:

Choroid plexus pseudocyst in the inferolateral aspect of atrium (? corpus striatum) on oblique coronal plane, which elongates by turning transducer

Choroid Plexus Papilloma

Incidence:	0.5 0.6% of all primary intracranial tumors; 2 5% of brain tumors in childhood; 5% of all supratentorial tumors in children; 60 70% of tumors of the choroids
Age:	20 40% <1 year of age; 86% <5 years of age; in 75% <2 years of age; M >> F
Path:	large aggregation of choroidal fronds producing great quantities of CSF; occasionally found incidentally on postmortem examination
Pathophysiology:	abnormal rate of CSF production of 1.0 mL/min (normal rate = 0.2 mL/min)
May be associated with:	von Hippel-Lindau syndrome (papillomas in unusual locations)

• signs of increased intracranial pressure

Location:

• glomus of choroid plexus in trigone of lateral ventricles, L > R (in children)

• 4th ventricle + cerebellopontine angle (in adults)

• 3rd ventricle (unusual)

• multiple in 7%

• large mass with smooth lobulated border

• small foci of calcifications (common)

• engulfment of glomus of choroid plexus (distinctive feature)

• asymmetric diffuse ventricular dilatation = communicating hydrocephalus (CSF overproduction / decreased absorption secondary to obstruction of arachnoid granulations from repeated occult hemorrhage)

• dilatation of temporal horn in atrial location (obstruction)

• occasionally growth into surrounding white matter (more commonly a feature of choroid plexus carcinoma)

CT:

• iso- / mildly hyperdense homogeneous mass

CECT:

• intense homogeneous enhancement

MR:

• isointense / slightly hyperintense lesion on T1WI + slightly hypointense on T2WI relative to white matter

• surrounded by hypointense signal on T1WI + hyperintense signal on T2WI (CSF)

• intraventricular enhancing island of tumor on Gd-DTPA

US:

• echogenic mass adjacent to normal choroid plexus

Angio:

• supplied by anterior + posterior choroidal arteries

Cx:	(1) transformation into malignant choroid plexus papilloma = choroid plexus carcinoma (in 5%)
	(2) hydrocephalus (in children) secondary to increased intracranial pressure from CSF-overproduction
Rx:	surgical removal (24% operative mortality) cures hydrocephalus
DDx:	intraventricular meningioma, ependymoma, metastasis, cavernous angioma, xanthogranuloma, astrocytoma

Cockayne Syndrome

• = autosomal recessive diffuse demyelinating disease

Age:

beginning at age 1

• dwarfism

• progressive physical + mental deterioration

• retinal atrophy + deafness

• brain atrophy / microcephaly

• calcifications in basal ganglia + cerebellum

• skeletal changes superficially similar to progeria

DDx:

Progeria

Colloid Cyst

Incidence:	2% of glial tumors of ependymal origin; 0.5 1% of CNS tumors
Histo:	ciliated + columnar epithelium; mucin-secreting; squamous cells of ependymal origin; tough fibrous capsule
Age:	young adults; M > F

• positional headaches (transient obstruction secondary to ball-valve mechanism at foramen of Monro)

• gait apraxia

• change in mental status dementia (related to increased intracranial pressure)

• papilledema (may become medical emergency with acute herniation)

Location:

exclusively arising from inferior aspect of septum pellucidum protruding into anterior portion of 3rd ventricle between columns of fornix

• sellar erosion

• spherical iso- / hyperdense lesion on NCCT with smooth surface

• fluid contents:

  • in 20% similar to CSF (= isodense)

  P.278

  
  

  • in 80% mucinous fluid, proteinaceous debris, hemosiderin, desquamated cells (= hyperdense)

• may show enhancement of border (draped choroid plexus / capsule)

• 3rd ventricular enlargement (to accommodate cyst anteriorly)

• asymmetric lateral ventricular enlargement (invariably)

• occasionally widens septum pellucidum

• MR:

  • lesion hyperintense on T1WI + hyperintense on T2WI in 60% (related to large protein molecules / paramagnetic effect of magnesium, copper, iron in cyst)

DDx:

meningioma, ependymoma of 3rd ventricle (rare) with enhancement

Cortical Contusion

• = CEREBRAL CONTUSION = BRAIN CONTUSION

• = traumatic injury to cortical surface of brain

Incidence:	most common type of primary intraaxial lesion; in 21% of head trauma patients; children:adults = 2:1
Pathogenesis:	capillary disruption leads to extravasation of whole blood, plasma (edema) and RBCs
Path:	petechial hemorrhage (= admixture of blood with native tissue) followed by liquefaction + edema after 4 7 days, tissue necrosis
Mechanism:	linear acceleration-deceleration forces / penetrating trauma

• Coup (same side as impact)

  • = small area of direct impact on stationary brain

    Associated with:

    skull fracture

• Contrecoup (180 opposite to side of impact)

  • = broad area of impact as a result of moving brain against stationary calvarium

Associated with:	fall
Location:	multiple bilateral lesions;

• common: along anterior + lateral + inferior surfaces of frontal lobe (in orbitofrontal, inferior frontal, and rectal gyri above cribriform plate, planum sphenoidale, lesser sphenoid wing) and temporal lobe (just above petrous bone / posterior to greater sphenoid wing)

• less frequent: in parietal + occipital lobes, cerebellar hemispheres, vermis, cerebellar tonsils

• often bilateral / beneath an acute subdural hematoma

• confusion (mild initial impairment)

• focal cerebral dysfunction

• seizures, personality changes

• focal neurologic deficits (late changes)

• CT (sensitive only to hemorrhage in acute phase):

  • Look for scalp swelling to focus your attention on the location of the coup!

  • salt and pepper lesion = mottled / speckled densities as focal / multiple (29%) poorly defined areas of low attenuation with irregular contour (edema) intermixed with a few tiny areas of increased density (petechial hemorrhage)

  • diffuse cerebral hypodensity + swelling without hemorrhage in immediate posttraumatic period (common in children) due to hyperemia / ischemic edema

  • some degree of contrast enhancement (leaking new capillaries)

  • hemorrhage isodense after 2 3 weeks

  • true extent of lesions becomes more evident with progression of edema + cell necrosis + mass effect over ensuing weeks

• MR (best modality for initial detection of contusional edema + accurate portrayal of extent of lesions):

  • hemorrhagic lesions (detected in 50% of all contusions):

    • initially decreased intensity (deoxyhemoglobin of acute hemorrhage) surrounded by hyperintense edema on T2WI

    • hyperintense on T1WI + T2WI in subacute phase (secondary to Met-Hb)

    • hyperintense gliosis + hypointense hemosiderin on T2WI in chronic phase

  • nonhemorrhagic lesions hypointense on T1WI

  • + hyperintense on T2WI

Cx:	(1)	Progression to cerebral hematoma
	(2) Encephalomalacia (= scarred brain)
	(3) Porencephaly (= formation of cystic cavity lined with gliotic brain and communicating with ventricles / subarachnoid space)
	(4) Hydrocephalus as a result of adhesions caused by subarachnoid blood

Craniopharyngioma

Incidence:	3 4% of all intracranial neoplasms; 15% of supratentorial + 50% of suprasellar tumors in children; most common suprasellar mass
Origin:	from epithelial rests along vestigial craniopharyngeal duct (Rathke cleft / pouch within intermediate lobe of pituitary gland)
Path:	benign tumor originating from neuroepithelium in craniopharyngeal duct + primitive buccal epithelium
Histo:	cystic (rich in liquid cholesterol) / complex / solid
Age:	from birth 7th decade; bimodal age distribution: age peaks in 1st 2nd decade (75%) + in 5th decade (25%); M > F

• diabetes insipidus (compression of pituitary gland)

• growth retardation (compression of hypothalamus)

• bitemporal hemianopia (compression of optic nerve chiasm)

• headaches from hydrocephalus (compression of foramen of Monro / aqueduct of Sylvius)

Location:

• pituitary stalk / tuber cinereum

• suprasellar (20%)

• intrasellar (10%)

• intra- and suprasellar (70%)

• Ectopic craniopharyngioma:

  • (e) floor of anterior 3rd ventricle (more common in adults)

  • (f) sphenoid bone

• Skull films:

  • normal sella (25%)

  • enlarged J-shaped sella with truncated dorsum

  • thickening + increased density of lamina dura in floor of sella (10%)

  • extensive sellar destruction (75%)

  • curvilinear / flocculent / stippled calcifications / lamellar ossification; calcifications seen in youth in 70 90%, in adults in 30 40%

• CT:

  • multilobulated inhomogeneous suprasellar mass

  P.279

  
  

  • solid (15%) / mixed (30%) / cystic lesion (54 75%) [cystic appearance secondary to cholesterol, keratin, necrotic debris with higher density than CSF]

  • enhancement of solid lesion, peripheral enhancement of cystic lesion

  • marginal hyperdense lesion (calcification / ossification) in 70 90% in childhood tumors + 30 50% of adult tumors

  • obstructive hydrocephalus

  • extension into middle > anterior > posterior cranial fossa (25%)

• MR (relatively ineffective in demonstrating calcifications):

  • mostly hyperintense, but also iso- / hypointense on T1WI (variable secondary to hemorrhage / cholesterol-containing proteinaceous fluid)

  • markedly hyperintense on T2WI

  • marginal enhancement of solid components with gadopentetate dimeglumine

• Angio:

  • usually avascular

  • lateral displacement, elevation, narrowing of supraclinoid segment of ICA

  • posterior displacement of basilar artery

DDx:	(1) Epidermoid (no contrast enhancement)
	(2) Rathke cleft cyst (small intrasellar lesion)

Cysticercosis of Brain

Larva of pork tapeworm (Taenia solium) frequently involving CNS, eyes, muscle, heart, fat tissue, skin

• Route of infection:

  • Ingestion of ova by fecal-oral route via contaminated food / water or autoinfection; embryophore is dissolved by gastric acid and enzymes + oncosphere is liberated

  • Ingestion of undercooked contaminated pork containing cysticerci; tapeworm develops in intestinal lumen + releases eggs

• Organism:

  • embryos invade intestinal wall + enter circulation + disseminate in varies parts of body; embryo develops into a cysticercus (= complex wall surrounding a cavity containing vesicular fluid + scolex); following ingestion of cysticercus by definitive host a tapeworm develops within the intestinal tract

Incidence:	most common parasitic infection involving CNS in developing countries; CNS involvement in up to 90%
Endemic to:	Mexico, South America, Africa, eastern Europe, Asia, Indonesia
Location:	meninges (39%) esp. in basal cisterns, parenchyma (20%), intraventricular (17%), mixed (23%), intraspinal (1%)
	Seeding:	through subarachnoid space
		+ intraventricular system

• STAGE OF LARVAL TISSUE INVASION

  • asymptomatic

  • localized focus of edema on T2WI

  • nodular tissue enhancement

• VESICULAR STAGE

  • = antigenetically inert, therefore without inflammatory reaction / circumferential edema

  • asymptomatic

  • single / multiple thin-walled nonenhancing 4 20 mm spherical cysts:

    • center with clear fluid of CSF intensity

    • 2 3 mm mural nodule (= scolex) isointense with brain parenchyma

• COLLOIDAL STAGE

  • = scolex dies and its metabolic breakdown (colloidal suspension) results in focal meningoencephalitis with breakdown of blood-brain barrier

  • focal seizures (in endemic countries most common cause of adult-onset epilepsy)

  • headache, signs of increased intracranial pressure

  • avid ring-enhancing capsule on T1WI

  • center hypointense to white matter and hyperintense to CSF on T1WI + markedly hyperintense on T2WI (due to proteinaceous nature of cyst fluid)

  • hypointense mural nodule on T2WI with strong homogeneous enhancement

  • with extensive white matter edema (DDx: metastasis without edema)

• NODULAR-GRANULAR STAGE

  • = degeneration of cysticercus with mineralization

  • gradually subsiding perilesional edema

  • shrinkage of cyst becoming isointense with brain on T1WI + hypointense on T2WI

  • isoattenuating lesion with enhancement of thick nodular ring on CT

• CALCIFIED STAGE

  • = complete involution of lesion with continued mineralization

  • asymptomatic / posttreatment seizures

  • small focal calcifications; may appear within 8 months to 10 years after acute infection

  • ricelike muscle calcifications rarely visible

• RADIOGRAPHIC TYPES

  • Parenchymal type

    • multiple / solitary cystic lesions up to 6 cm in size: large cysts are usually multiloculated

    • many terminate as calcified granulomata (larvae not dead unless completely calcified)

    • encephalitic form may occur in children

  • Subarachnoid / racemose neurocysticercosis

    • = infiltration of basal cisterns + sylvian fissures associated with local meningeal inflammation / fibrosis

    • lucent cystic lesions up to several cm in basal cisterns (= racemose cysts) with variable enhancement, usually located in cerebellopontine angle / suprasellar cistern

      Cx:

      hydrocephalus; scattered infarctions (due to vasculitis of basal perforating vessels)

  • Intraventricular neurocysticercosis

    • obstructive hydrocephalus caused by blockage within various portions of ventricular system from solitary / multiple cysts (OCCULT on CT!)

  • Mixed type (frequent)

Cytomegalovirus Infection

• = double-stranded DNA virus with replication inside cell nucleus causing a lytic productive / latent infection; member of Herpes viridae family (with varicella-zoster virus, Epstein-Barr virus, herpes simplex virus types 1 and 2)

P.280




• Most common intrauterine infection!

  Incidence:

  0.4 2.4% of liveborn infants; 40,000 babies born each year with CMV infection

  • Transmission:

    • horizontally by contact with saliva / urine or sexually

    • vertically from mother to fetus transplacentally; spreads hematogenously throughout fetus

      • Severe fetal morbidity if infected during first half of pregnancy!

    Histo:	necrotizing inflammatory process
    Predilection:	CMV has special affinity for metabolically active neuroblasts of germinal matrix

  • Prenatal screening:

    • antibodies in 30 60% of pregnant women;

    • primary CMV infection in 2.5% of pregnant women

  • Postnatal screening:

    • 10% of neonates excrete virus;

    • 1.6% of newborns shed CMV in urine / saliva

  • asymptomatic + subclinical (90%)

  • symptomatic at birth (5 10%):

    • sensorineural deafness, mental retardation, neurologic deficits, seizures

    • ocular abnormalities (15 50%): chorioretinitis, optic neuritis, optic atrophy, hypoplasia + coloboma of optic nerve, anterior uveitis, anophthalmia, microphthalmia, cataracts, cyclopia

    • jaundice, hemolytic anemia, thrombocytopenic purpura

    • Leading cause of brain disease + hearing loss in children!

  • symptomatic in adults (in up to 15%):

    • fever, pharyngitis, lymphadenopathy, polyarthritis

    • intrauterine growth retardation

    • hepatosplenomegaly (nontender)

    • ascites

    • hydrops

    • pneumonitis

  • @ CNS

    • periventricular subependymal cysts (= focal areas of necrosis + glial reaction)

    • intracranial calcifications:

      • periventricular postinflammatory calcifications

      • scattered calcifications in basal ganglia + thalami

      • highly echogenic thickened walls of lenticulostriate vessels (= mineralized vasculopathy with deposition of amorphous basophilic material in arterial walls)

      • calcifications throughout brain parenchyma

    • ventricular dilatation (due to ventriculitis / obstruction by inflammatory exudate / brain atrophy)

    • intraventricular septa

    • microcephaly (due to encephaloclastic effect of virus / disturbance of cell proliferation resulting in brain atrophy)

    • lissencephaly, cortical dysplasia / atrophy, heterotopia, polymicrogyria, schizencephaly (due to disturbed neuronal migration)

    • severe diffuse hypoplasia / dysplasia of cerebellum

Dx:	positive viral culture within first 2 weeks of life
Rx:	no effective treatment for maternal infection
DDx:	toxoplasmosis, teratoma, tuberous sclerosis, Sturge-Weber syndrome, venous sinus thrombosis

Dandy-Walker Malformation

= characterized by (1) enlarged posterior fossa with high position of tentorium (2) dys- / agenesis of cerebellar vermis (3) cystic dilatation of 4th ventricle filling nearly entire posterior fossa

Incidence:	12% of all congenital hydrocephaly
Path:	defect in vermis connecting an ependyma-lined retrocerebellar cyst with 4th ventricle (PATHOGNOMONIC)
Cause:	dysmorphogenesis of roof of 4th ventricle with failure to incorporate the area membranacea into developing choroid plexus; proposed originally as congenital atresia of foramina of Luschka (lateral) + Magendie (median) not likely since foramina are not patent until 4th month

• Associated anomalies:

  • midline CNS anomalies (in >60%)

    • Dysgenesis of corpus callosum (20 25%), lipoma of corpus callosum

    • Holoprosencephaly (25%)

    • Malformation of cerebral gyri (dysplasia of cingulate gyrus) (25%)

    • Cerebellar heterotopia + malformation of cerebellar folia (25%)

    • Malformation of inferior olivary nucleus

    • Hamartoma of tuber cinereum

    • Syringomyelia

    • Cleft palate

    • Occipital encephalocele (<5%)

  • other CNS anomalies:

    • Polymicrogyria / gray matter heterotopia (5 10%)

    • Schizencephaly

    • Lumbosacral meningocele

  • non-CNS anomalies (25%)

    • Polydactyly, syndactyly

    • Klippel-Feil syndrome

    • Cornelia de Lange syndrome

    • Cleft palate

    • Facial angioma

    • Cardiac anomalies

  • Skull film:

    • large skull secondary to hydrocephalus + dolichocephaly

    • diastatic lambdoid suture

    • disproportionately large expanded posterior fossa

    • torcular herophili and lateral sinuses high above lambdoid angle = torcular-lambdoid inversion

  • CT / US / MR:

    • absence / hypoplasia of cerebellar vermis; total (25%), partial (75%)

    • superiorly displaced superior vermis cerebelli

    • small + widely separated cerebellar hemispheres

    • anterior + lateral displacement of hypoplastic cerebellar hemispheres

    • large posterior fossa cyst with extension through foramen magnum = diverticulum of roofless 4th ventricle

    • elevated insertion of tentorium cerebelli

    • cerebellar hemispheres in apposition without intervening vermis following shunt procedure

    • absence of falx cerebelli

    • scalloping of petrous pyramids

    P.281

    
    

    • ventriculomegaly (in 72% open communication with 3rd ventricle; in 39% patent 4th ventricle; in 28% aqueductal stenosis; in 11% incisural obstruction); present prenatally in 30%, by 3 months of age in 75%

    • anterior displacement of pons

  • Angio:

    • high position of transverse sinus

    • elevated great vein of Galen

    • elevated posterior cerebral vessels

    • anterosuperiorly displaced superior cerebellar arteries above the posterior cerebral arteries

    • small / absent PICA with high tonsillar loop

    Cx:	trapping of cyst above tentorium = keyhole configuration
    Prognosis:	fetal demise in 66%; 22 50% mortality during 1st year of life
    DDx:	(1) Posterior fossa extra-axial cyst
    	(2) Arachnoid cyst (normal 4th ventricle, patent foramina, intact vermis)
    	(3) Isolated 4th ventricle
    	(4) Megacisterna magna = giant cisterna magna (enlarged posterior fossa, enlarged cisterna magna, intact vermis, normal 4th ventricle)
    	(5) Porencephaly

Dandy-Walker Variant

• characterized by

  • variable hypoplasia of posteroinferior portion of vermis leading to communication between 4th ventricle and cisterna magna

  • cerebellar dysgenesis

  • cystic dilatation of 4th ventricle

  • NO enlargement of posterior fossa

• More common than Dandy-Walker malformation; accounts for 1/3 of all posterior fossa malformations

  Cause:

  focal insult to developing cerebellum

• Associated CNS anomalies:

  • agenesis of corpus callosum (21%), cerebral gyral malformation (21%), heterotopia, holoprosencephaly (10%), diencephalic cyst (10%), posterior fossa meningoencephalocele (10%)

• Other associated anomalies:

  • polydactyly; cardiac, renal, facial anomalies; abnormal karyotype (29%)

  • 4th ventricle smaller + better formed

  • retrocerebellar cyst smaller

  • communication between retrocerebellar cyst and subarachnoid space through a patent foramen of Magendie may be present

  • posterior fossa smaller than in usual Dandy-Walker syndrome

• OB-US:

  • incomplete closure of vermis is normal until 18 weeks GA!

Dandy-Walker Complex

• = continuum of anomalies, including Dandy-Walker malformation + Dandy-Walker variant + megacisterna magna, characterized by partial / complete dysgenesis of vermis cerebelli

  Cause:

  broad insult to alar plate from a variety of abnormalities

• Associated with:

  • Inherited genetic syndromes

    • autosomal recessive:

      • Meckel-Gruber syndrome

      • Ellis-van Creveld syndrome

      • Walker-Warburg syndrome

    • autosomal dominant:

      • X-linked cerebellar hypoplasia

      • Aicardi syndrome

  • Abnormal karyotype (33%)

    • Duplications of chromosomes 5p, 8p, 8q

    • Trisomies 9, 13, 18

  • Infection

    • Virus: CMV, rubella

    • Protozoan: toxoplasmosis

  • Teratogen: alcohol, sodium warfarin

  • Multifactorial

Pseudo-Dandy-Walker Malformation

• = developing normal rhombencephalon during 1st trimester

• fluid-filled space in posterior aspect of fetal head

Dermoid of CNS

• = pilosebaceous mass lined with skin appendages originating from inclusion of epithelial cells + skin appendages during closure of neural tube

  Incidence:	1% of all intracranial tumors
  Path:	ectodermal + mesodermal lesion = squamous epithelium, mesodermal cells (hair follicles, sweat + sebaceous glands)
  Age:	<30 years (appears in adulthood secondary to slow growth); M < F

• Location:

  • spinal canal (most common): extra- / intramedullary in lumbosacral region

  • posterior fossa within vermis / 4th ventricle (predilection for midline)

  • posterior to superior orbital fissure, may be associated with bone defect

• bouts of chemical / bacterial meningitis possible

  thick-walled inhomogeneous mass with focal areas of fat

  mural / central calcifications / bone (possible)

  may have sinus tract to skin surface (dermal sinus) if located in midline at occipital / nasofrontal region

  fat-fluid level if cyst ruptures into ventricles, fat droplets in subarachnoid space

  NO contrast enhancement

• MR:

  • variointense on T1WI (hyperintense with contents of liquefied cholesterol products)

  • shortened T1 + T2 relaxation times (= fat)

Diffuse Axonal Injury

• = WHITE MATTER SHEARING INJURY

  Incidence:

  most common type of primary traumatic injury in patients with severe head trauma (48%)

  P.282

  
  

  Cause:

  high-velocity trauma (MVA) resulting in indirect injury due to rotational / angular (especially coronal) acceleration / deceleration forces (direct impact to head or fracture not required)

• Pathogenesis:

  • cortex and deep structures move at different speed causing shearing stress of

    • axons resulting in axonal tears followed by wallerian degeneration

    • small white-matter vessels resulting in small petechial hemorrhages

  Path:	much of the injury is only microscopic
  Histo:	multiple axonal retraction balls (HALLMARK), numerous perivascular hemorrhages

• immediate severe impairment of consciousness at time of impact

• persistent vegetative state

• Location (according to severity of trauma):

  • lobar white matter at corticomedullary junction (67%): parasagittal region of frontal lobe + periventricular region of temporal lobe; occasionally in parietal + occipital lobes

  • internal + external capsule / basal ganglia, corona radiata, cerebellar peduncles

  • corpus callosum (21%): 3/4 of lesions at undersurface of posterior body + splenium

    • often associated with intraventricular hemorrhage

  • brainstem: posterolateral quadrants of midbrain + upper pons; superior cerebellar peduncles especially vulnerable

• sparing of cortex

• 20% of lesions with small central areas of petechial hemorrhage

• CT (negative in 30% of positive MR cases):

  • foci of decreased density (usually seen when >1.5 cm in size)

• MR (most sensitive modality):

  • multiple small oval / round foci of decreased signal intensity on T1WI + increased signal on T2WI

• Prognosis:

  • poor due to sequelae (may go on to die without signs of high intracranial pressure)

  • brain atrophy with enlargement of sulci + ventricles

Diffuse Sclerosis

sporadic, young adults, fulminant course

• dementia, deafness

  low-attenuation regions in both hemispheres without symmetry

Dural Sinus Thrombosis

• = Venous / Superior Sagittal Sinus Thrombosis

• The radiologist may be the first to suggest the diagnosis!

• Cause:

  • Idiopathic = spontaneous (10 30%)

  • Septic causes (esp. in childhood):

    • sinusitis, otitis, mastoiditis, sub- / epidural empyema, meningitis, encephalitis, brain abscess, face + scalp cellulitis, septicemia

  • Aseptic causes:

    • Tumor compressing sinus: meningioma, blastic crisis of chronic myelogenous leukemia

    • Trauma: fracture through sinus wall, cranial surgery, jugular vein catheterization

    • Low-flow state: CHF, CHD, dehydration, shock

    • Hypercoagulability: antithrombin III deficiency, antiphospholipid syndrome, protein S deficiency, protein C resistance, pregnancy, peripartum state, oral contraceptives, polycythemia vera, idiopathic thrombocytosis, thrombocytopenia, sickle cell disease, cryofibrinogenemia, disseminated intravascular coagulopathy

    • Chemotherapy: eg, ARA-C, L-asparaginase

  • Unusual causes:

    • Beh et disease. AIDS, ulcerative colitis, systemic lupus erythematosus, nephrotic syndrome, sarcoidosis

  • Pathophysiology:

    • dural sinus thrombosis leads to venous congestion, cerebral venous infarction, brain edema, sulcal effacement, hemorrhage, occasionally hydrocephalus (due to decreased CSF absorption)

    • symptoms of increased intracranial pressure: headaches, nausea, vomiting, visual blurring, papilledema

      often confused with:

      tension headaches, migraine

    • drowsiness, confusion, decreased mentation, lethargy, obtundation

    • stroke symptomatology (dysphasia, cranial nerve palsy, cerebellar incoordination), seizures

    • fever

      Location:

      superior sagittal > transverse > sigmoid > straight sinus

    • NCCT (usually subtle findings):

      • hyperattenuating material (clotted blood) in sagittal sinus / straight sinus / cerebral cortical veins = dense triangle sign / cord sign (20%)

      • compression of lateral ventricles in 32% (infarction / edema)

      • unilateral (2/3) / bilateral (1/3) parenchymal hemorrhage involving gray + white matter (20%)

      • subdural collection

      • stroke (often hemorrhagic)

    • CECT venography (30 40 sec delay):

      • empty delta sign / empty triangle = filling defect in straight sinus / superior sagittal sinus surrounded by a triangular area of enhancement (in 25 35 70%)

        False positive:	subdural hematoma / empyema, arachnoid granulations
        False negative:	partial volume averaging, small thrombus, recanalized thrombus

      • enlargement of thrombosed vein near obstruction

      • shaggy irregular contour of veins (= small collateral veins enhance near the obstructed vein)

      • gyral enhancement in periphery of infarction (30 40%)

      • intense tentorial enhancement secondary to collaterals (rare)

      • dense transcortical medullary vein

      Advantages over MRI:

      shorter exam time

    • MR:

      • replacement of flow void by abnormal signal intensity

        • acute thrombosis (first few days)

          • clot isointense to gray matter on T1WI (and therefore easily missed) + hypointense on T2WI

          P.283

          
          

          • low signal intensity rather than normal flow void on T1WI

        • chronic thrombosis (when most cases are diagnosed)

          • hyperintense thrombus within sinus on T1WI (due to intra- and extracellular methemoglobin)

          • iso- / hyperintense thrombus on T2WI (due to extracellular methemoglobin)

            N.B.:

            hypointense thrombus on T2WI (due to intracellular methemoglobin) may mimic flow void of a patent dural sinus

        • subcortical hemorrhagic infarcts (due to retrograde extension of thrombus)

        • wall-enhancement of thrombosed dural sinus

      • MR venography:

        • absence of flow-related enhancement

          Pitfall:

          hyperintense thrombus on T1WI time-of-flight venography can simulate flow-related enhancement

      • Angio:

        • nonfilling of thrombosed sinus

        • filling of cortical veins, deep venous system, cavernous sinus

        • parasagittal hemorrhages (highly specific for superior sagittal sinus thrombosis) secondary to cortical venous infarction

        Prognosis:	high mortality
        Rx:	heparin (full recovery in 70%)

Dyke-Davidoff-Mason syndrome

• = CEREBRAL hemiatrophy = INFANTILE / CONGENITAL HEMIPLEGIA = SYNDROME OF hemiconvulsions, HEMIPLEGIA, AND EPILEPSY

• = unilateral cerebral atrophy with ipsilateral small skull

  Cause:	insult to immature brain resulting in neuronal loss + impaired brain growth: prenatal: congenital malformation, infection, vascular insult perinatal: birth trauma, anoxia, hypoxia, intracranial hemorrhage postnatal: trauma, tumor, infection, prolonged febrile seizures
  Age:	presents in adolescence

• seizures

• hemiparesis (typically spastic hemiplegia)

• mental retardation

• unilateral thickening of skull

• unilateral decrease in size of cranial fossa

• unilateral overdevelopment of sinuses

• contraction of a hemisphere / lobe

• compensatory enlargement of adjacent ventricle + sulci with midline shift

Dysembryoplastic Neuroepithelial Tumor

• = benign tumor of neuroepithelial origin arising from cortical / deep gray matter

  Origin:	derived from secondary germinal layers; originally diagnosed as low-grade astrocytomas
  Histo:	specific glioneuronal element in a columnar pattern oriented perpendicular to cortical surface; admixture of astrocytes + oligodendroglial elements in association with floating neurons and mucinous degeneration; multinodular architecture
  Age:	usually <20 years; M > F

• medically refractory partial seizures

• neurologic deficits rare

  Location:

  temporal (62%) / frontal (31%) lobe; caudate nucleus; cerebellum; pons

• CT:

  • hypoattenuating mass calcifications

  • remodeling of inner table of skull

• MR:

  • cortical mass without surrounding vasogenic edema:

    • hypointense on T1WI + hyperintense on T2WI

    • soap bubble / megagyrus appearance at cortical margin

      • = enlargement of cortical surface

    • contrast enhancement (in 33%)

      Prognosis:	partial resection stops seizure activity; rarely recur
      DDx:	diffuse astrocytoma, ganglioglioma, oligodendroglioma

Empty Sella Syndrome

• = extension of subarachnoid space into sella turcica, which becomes exposed to CSF pulsations secondary to defect in diaphragma sellae; characterized by normal / molded pituitary gland + normal or enlarged sella (empty sella = misnomer)

• Incidence:

  24% in autopsy study

  • slowly progressive symmetrical / asymmetrical (double floor) enlargement of sella

  • remodeled lamina dura remains mineralized

  • small rim of pituitary tissue displaced posteriorly + inferiorly

  • infundibulum sign = infundibulum extends to floor of sella

• DDx:

  cystic tumor, large herniated 3rd ventricle (displaced infundibulum)

Primary Empty Sella (anatomic spectrum)

Incidence:

10% of adult population; M:F = 1:4

• Probable causes:

  • pituitary enlargement followed by regression during pregnancy

  • involution of a pituitary tumor

  • congenital weakness of diaphragma sellae

• Occurs more frequently in patients with increased intracranial pressure

• usually asymptomatic

• increased risk for CSF rhinorrhea

• NO endocrine abnormalities

Secondary Empty Sella

• = postsurgical when diaphragma sellae has been disrupted

• visual disturbance

• headaches

Empyema of Brain

Cause:

paranasal sinusitis, otitis media, calvarial osteomyelitis, infection after craniotomy or ventricular shunt placement, penetrating wound, contamination of meningitis-induced subdural effusion

P.284

Subdural Empyema

• 20% of all intracranial bacterial infections

  Location:

  frontal + inferior cranial space in close proximity to paranasal sinuses; 80% over convexity extending into interhemispheric fissure or posterior fossa

• hypo- / isodense crescentic / lentiform zone adjacent to inner table

• may show mass effect (sulcal effacement, ventricular compression, shift)

• thin curvilinear rim of enhancement (7 10 days later) adjacent to brain

• severe sinusitis / mastoiditis (may be most significant indicator)

  Mortality:	30% (neurosurgical emergency)
  Cx:	venous thrombosis, infarction, seizures, hemiparesis, hemianopia, aphasia, brain abscess
  DDx:	subacute / chronic subdural hematoma

Epidural Empyema

• no neurologic deficits (dura minimizes pressure exerted on brain)

  thick enhancing rim

Encephalitis

• = term generally reserved for diffuse inflammatory process of viral etiology, most commonly arthropod-borne arboviruses (Eastern + Western equine encephalitis, California virus encephalitis, St. Louis encephalitis)

• diffuse mild cerebral edema

• small infarctions / hemorrhage (less frequent)

• hyperintensity on T2WI in areas of cortical involvement

Herpes Simplex Encephalitis (HSE)

• = most common cause of nonepidemic necrotizing meningoencephalitis in immunocompetent individuals in USA

• Neurologic emergency due to high morbidity + mortality

  Organism:

  HSV type I (in adults); HSV type II (in neonates from transplacental infection)

• preceding viral syndrome

• mental status changes: confusion, disorientation, hallucination, personality change, aphasia

• low-grade fever, headache, seizures

  Location:

  inferomedial temporal > frontal > parietal lobes; propensity for limbic system (olfactory tract, temporal lobes, cingulate gyrus, insular cortex); initially predominantly unilateral

• mild patchy peripheral / gyral / cisternal enhancement (50%), may persist for several months

• CT:

  • may be negative in first 3 days

  • poorly defined bilateral areas of mildly decreased attenuation in one / both temporal lobes + insulae

  • spared putamen forms sharply defined concave / straight border (DDx: infarction, glioma)

  • mild mass effect with compression of lateral ventricles + loss of sylvian fissure (brain edema)

  • tendency for hemorrhage + rapid dissemination in brain

• MR (study of choice, positive within 2 days):

  • increased signal intensity on T2WI + mild to moderate hypointensity on T1WI

  • increased signal on diffusion-weighted images (cytotoxic edema)

  • small foci of hemorrhage (common)

• NUC:

  • Agents:

    standard brain imaging (eg, Tc-99m DTPA), newer brain agents (eg, I-123 iodoamphetamine / Tc-99m HMPAO)

  • SPECT imaging improves sensitivity

  • characteristic focal increase in activity in temporal lobes on brain scintigraphy (blood-brain barrier breakdown)

• Dx:	(1) identification of virus within CSF (using polymerase chain reaction technique)
  	(2) fluorescein antibody staining / viral culture from brain biopsy

• Mortality:

  30 70%

• Rx:

  adenine arabinoside

• DDx:	(1) Infarction (involves either medial or lateral temporal lobe, almost exclusively unilateral)
  	(2) Low-grade glioma
  	(3) Abscess

Human Immunodeficiency Virus Encephalitis

• often in combination with CMV encephalitis

• Histo:

  microglial nodules + perivascular multinucleated giant cells accompanying gliosis of deep white + gray matter

• predominantly central CNS atrophy

• symmetric periventricular / diffuse white matter disease without mass effect (hypodense on CT, high intensity on T2WI)

Postinfectious Encephalitis

• following exanthematous viral illness (measles, mumps, rubella, smallpox, chickenpox, Epstein-Barr virus, varicella, pertussis) / vaccination

Acute Disseminated Encephalomyelitis (ADEM)

• = postviral leukoencephalopathy

• = autoimmune reaction against patient's white matter

• 7 14 days / several weeks following an exanthematous viral infection / vaccination

• confusion, headaches, fever

• seizures, focal neurologic deficits

• Histo:	diffuse perivenous inflammatory process resulting in areas of demyelination
  Location:	subcortical white matter of both hemispheres asymmetrically; may involve brainstem / posterior fossa

• lesions may demonstrate contrast enhancement

• CT:

  • multifocal hypodense white matter abnormalities

  • sparing of cortical gray matter, occasionally deep gray matter involvement

  • no additional lesions on follow-up exam

• MR:

  • multifocal punctate / large confluent areas of hyperintensity on FLAIR / T2WI

  • Rx:

    corticosteroids result in dramatic improvement

  P.285

  
  

  Prognosis:	complete resolution of neurologic deficits within 1 month (80 90%) / some permanent neurologic damage (10 20%)
  DDx:	multiple sclerosis (rarely recurrent episodes as in multiple sclerosis); autoimmune vasculitis; aging brain

Acute Hemorrhagic Leukoencephalitis

• = fulminant myelinoclastic disease of CNS

• = hyperacute form of acute disseminated encephalomyelitis

• Cause:	immunoreactive disease following prodromal illness (minor upper respiratory viral infection, ulcerative colitis)
  Path:	marked edema, brain softening
  Histo:	necrotizing angitis of venules + capillaries within white matter with extravasation of PMNs + lymphocytes; fibrinoid necrosis of affected capillaries + surrounding tissues; confluent hemorrhages with ball-and-ring configuration due to diapedesis of RBCs

• progressive coma, motor disturbance, speech difficulty, seizures

• pyrexia, leukocytosis

• pleocytosis, elevated protein in spinal fluid

• Location:

  unilateral disease; parietal + posterior frontal white matter at level of centrum semiovale (sparing subcortical U-fibers + cortex) > basal ganglia, cerebellum, brainstem, spinal cord

• rapid development of profound mass effect resembling infarction

• multiple punctate white matter hemorrhages

• extensive hypoattenuation virtually confined to hemispheric white matter

• Prognosis:	usually results in death
  DDx:	(1) Herpes simplex encephalitis (cortical lesions in temporal + inferior frontal lobes + insular region, no imaging findings until 3 5 days after onset of significant symptoms)
  	(2) Tumefactive multiple sclerosis
  	(3) Osmotic demyelination
  	(4) Toxic encephalopathy: lipophilic solvent, methanol
  	(5) Hypertensive encephalopathy: eclampsia, thrombotic thrombocytopenic purpura

Ependymoma

• = in majority benign slow-growing neoplasm of mature well-differentiated ependymal cells lining the ventricles

• Incidence:	most commonly in children; 5 9% of all primary CNS neoplasms; 15% of posterior fossa tumors in children; 63% of spinal intramedullary gliomas
  Histo:	benign aggregates of ependymocytes in form of perivascular pseudorosettes; may have papillary pattern (difficult DDx from choroid plexus papilloma)
  Age:	(a) supratentorial: at any age (atrium / foramen of Monro)
  	(b) posterior fossa: <10 years; age peaks at 5 and 34 years; M:F = 0.8:1
  Associated with:	neurofibromatosis

• increased intracranial pressure (90%)

• Location:

  • (a) infratentorial: floor of 4th ventricle (70% of all intracranial ependymomas)

  • (b) supratentorial: frontal > parietal > temporoparietal juxtaventricular region (uncommonly intraventricular), lateral ventricle, 3rd ventricle

  • (c) conus (40 65% of all spinal intramedullary gliomas)

  • in children: infratentorial in 70%, supratentorial in 30%

• small cystic areas in 15 50% (central necrosis)

• fine punctate multifocal calcifications (25 50%)

• intratumoral hemorrhage (10%)

• frequently grows into brain parenchyma extending to cortical surface (particularly in frontal + parietal lobes)

• may invaginate into ventricles

• expansion frequently through foramen of Luschka into cerebellopontine angle (15%) or through foramen of Magendie caudad into cisterna magna (up to 60%) (CHARACTERISTIC)

• direct invasion of brainstem / cerebellum (30 40%)

• insinuation around blood vessels + cranial nerves

• communicating hydrocephalus (100%) secondary to protein exudate elaborated by tumor clogging resorption pathways

• CT:

  • sharply marginated multilobulated iso- / slightly hyperdense 4th ventricular mass

  • thin well-defined low-attenuation halo (distended effaced 4th ventricle)

  • heterogeneous / moderately uniform enhancement of solid portions (80%)

• MR:

  • low to intermediate heterogeneous signal intensity on T1WI

  • hypointense tumor margins on T1WI + T2WI in 64% (hemosiderin deposits)

  • foci of high-signal intensity on T2WI (= necrotic areas / cysts) + low signal intensity (= calcification / hemorrhage)

  • fluid-fluid level within cysts

  • homogeneous Gd-DTPA enhancement of tumor

• Cx:	subarachnoid dissemination via CSF (rare) (DDx: malignant ependymoma, ependymoblastoma)
  Rx:	surgery (difficult to resect due to adherence to surrounding brain) + radiation (partially radiosensitive) + chemotherapy

• DDx of cerebellar ependymoma:

  • Astrocytoma (hypodense, displaces 4th ventricle from midline, cystic lucency, intramedullary)

  • Medulloblastoma (hyperdense, calcifications in only 10%)

  • Trapped 4th ventricle (no contrast enhancement)

Epidermoid of CNS

• = EPIDERMOID [INCLUSION] CYST

• = benign tumor with extremely slow linear growth resulting from desquamation of epithelial cells from tumor wall

• Incidence:	0.2 1.8% of all primary intracranial neoplasms; most common congenital intracranial tumor
  Etiology:	inclusion of ectodermal epithelial tissue from pharyngeal pouch of Rathke / pluripotential cells during closure of neural tube in 5th week of fetal life (early inclusion results in midline lesion, later inclusion results in more lateral location)

P.286

• Path:	pearly tumor = well-defined solid lesion with glistening irregular nodular surface; soft flaky desquamated keratinaceous debris rich in cholesterol + triglycerides = PRIMARY / CONGENITAL CHOLESTEATOMA
  Histo:	tumor lined by simple stratified cuboidal squamous epithelium; surrounded by thin band of collagenous connective tissue; tumor center of lamellar appearance due to desquamation
  Age:	10 60 years, peak age in 4th 5th decade; tumor slowly expands over decades by continued desquamation of the lining thus becoming symptomatic in adulthood; M:F = 1:1

• facial pain

• cranial nerve palsies from CP angle epidermoids (50%)

• hydrocephalus in suprasellar epidermoids

• chemical meningitis (secondary to leakage of tumor contents into subarachnoid space) in middle cranial fossa epidermoids

• Site:

  midline / paramidline; intradural (90%) / extradural; transspatial growth (= extension from one into another intracranial space)

• Location:

  • cerebellopontine angle (40%, account for 5% of CP angle tumors)

  • suprasellar region, perimesencephalic cisterns (14%)

  • in ventricles, brainstem, brain parenchyma

  • skull vault

• soft lesion conforming to + molding itself around brain surfaces

• may intimately surround vessels + cranial nerves rather than displacing them (limited resectability)

• little mass effect, no edema / hydrocephalus

• NO contrast enhancement

• may be associated with dermal sinus tract at occipital / nasofrontal region if midline in location

• CT:

  • typically lobulated round homogeneous mass with density similar to CSF (between water and 20 HU)

  • occasionally hyperdense due to high protein content, saponification of keratinaceous debris, prior hemorrhage into cyst, ferrocalcium / iron-containing pigment, abundance of PMNs

  • bony erosion with sharply defined well-corticated margins

  • calcification (25%)

  • peripheral enhancement (perilesional inflammation)

• MR:

  • lamellated onionskin appearance with septations (layer-on-layer accretion of desquamated material)

  • black epidermoid = signal intensity similar to CSF: heterogeneously hypointense lesion on T1WI + hyperintense on T2WI (due to cholesterol in solid crystalline state + keratin within tumor + CSF within tumor interstices)

  • white epidermoid (rare) = hyperintense on T1WI + isointense on T2WI due to presence of triglycerides + polyunsaturated fatty acids

  • hypointense on T2WI (very rare) due to calcification, low hydration, viscous secretion, paramagnetic iron-containing pigment

• Angio:

  • avascular

• Cisternography:

  • papillary / frondlike surface with contrast material extending into tumor interstices

• Rx:	surgical resection (complicated by adherence to surrounding brain + cranial nerves, spillage of cyst contents with chemical meningitis, CSF seeding + implantation)
  DDx:	arachnoid cyst (smooth surface, earlier diffusion), cystic schwannoma, adenomatoid tumor, atypical meningioma, chondroma, chondrosarcoma, chordoma, calcified neurogenic tumor, teratoma, calcified astrocytoma, ganglioglioma

Epidural Hematoma of Brain

• = EXTRADURAL HEMATOMA

• = hematoma within potential space between naked inner table of skull + calvarial periosteum (inner dura layer), which is bound down firmly to cranium at sutural margins (= subperiosteal hematoma of inner table)

• Incidence: 2% of all serious head injuries; in <1% of all children with cranial trauma; uncommon in infants
  Cause:	impact on skull causes laceration of periosteal layer of outer table + linear fracture; temporary inward displacement of fragments lacerates meningeal vessels and strips both dural layers from inner table while the inner layer (meningeal dura) remains intact; blood accumulates between naked inner table and dura
  Age:	more common in younger patients 20 40 years (dura more easily stripped away from skull)

• Associated with:

  • skull fracture in 75 85 95% (best demonstrated on skull radiographs)

    • Skull fractures frequently not visible in children ( ping-pong fracture )!

  • subdural hemorrhage

  • contusion

• Source of bleeding:

  • laceration of (middle) meningeal artery (high pressure) / meningeal vein (low pressure) adjacent to inner table from calvarial fracture (91%)

  • disruption of dural venous sinuses (transverse / superior sagittal sinus) with low pressure + high flow due to diastatic fracture of lambdoid / coronal suture [major cause in younger children]

  • avulsion of diploic veins / marrow sinusoids at points of calvarial perforations

• Time of presentation:

  within first few days of injury (80%), 4 21 days (20%)

• transient loss of consciousness (= brief period of unconsciousness from concussion of brainstem)

• lucid interval (in <33%)

• delayed somnolence (24 96 hours after accident) due to accumulation of epidural hematoma:

  • DANGEROUS because of focal mass effect + rapid onset (neurosurgical emergency unless small)!

• progressive deterioration of consciousness to coma

• focal neurologic signs: 3rd nerve palsy (sign of cerebral herniation), hemiparesis

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• Only a minority of skull fractures across the middle meningeal artery groove result in epidural hematoma!

• Types:

  • I	acute epidural hematoma	(58%) from arterial bleeding
    II	subacute hematoma	(31%)
    III	chronic hematoma	(11%) from venous bleeding

  • Factors determining the rate of epidural expansion:

    • injury to artery or vein, spasm of artery, containment of bleed through pseudoaneurysm or tamponade, decompression of hematoma into meningeal + diploic veins or through fracture into scalp

• Location:

  • Most commonly clinically significant if located in temporoparietal region!

  • (a) in 66% temporoparietal (most often from laceration of middle meningeal artery)

  • (b) in 29% at frontal pole, parieto-occpital region, between occipital lobes, posterior fossa (most often from laceration of dural sinuses by fracture)

  • NO crossing of sutures unless diastatic fracture of suture present!

• CT:

  • fracture line in area of epidural hematoma

  • expanding biconvex (lenticular = elliptical) extra-axial fluid collection (most frequent) = under high pressure:

    • usually does not cross suture lines

    • separation of venous sinuses / falx from inner table

      • The ONLY hemorrhage displacing falx / venous sinuses away from inner table!

  • hematoma usually homogeneous:

    • fresh extravasated blood (30 50 HU) / coagulated blood (50 80 HU) in acute stage

    • rarely with hypoattenuated swirl (due to admixture of fresh blood into clotted blood in active bleeding)

  • mass effect ( compression cone effect ) with effacement of gyri + sulci from:

    • epidural hematoma (57%)

    • hemorrhagic contusion (29%)

    • cerebral edematous swelling (14%)

  • marked stretching of vessels

  • signs of arterial injury (rare): contrast extravasation, arteriovenous fistula, middle meningeal artery occlusion, formation of pseudoaneurysm

• MR:

  • low intensity of fibrous dura mater allows differentiation of epidural from subdural blood in the late subacute phase (extracellular methemoglobin) with hyperintensity on T1WI + T2WI

• Angio:

  • meningeal arteries displaced away from inner table of skull

  • pseudoaneurysm = extravasation of contrast material

  • arteriovenous fistula at fracture line

• Cx:	herniation, coma, death (15 30%)
  Rx:	after surgical evacuation return of ventricular system to midline

  • Epidural hematoma at another site may be unmasked following surgical decompression!

• DDx:

  Chronic subdural hematoma (may have similar biconvex shape, crosses suture lines, stops at falx, no associated skull fracture, no displaced dura on MRI)

Ganglion Cell Tumor

Gangliocytoma

• = rare benign tumor composed of mature ganglion cells

• Prevalence:	0.1 0.5% of all brain tumors
  Age:	children + young adults
  Associated with:	dysplastic + malformed brain
  Cause:	? dysplastic brain
  Histo:	purely neuronal tumor composed of abnormal mature ganglion cells without neoplastic glial cells (= no immunoreactivity for glial fibrillary acidic protein)
  Location:	floor of 3rd ventricle > temporal lobe > cerebellum > parieto-occiptal region > frontal lobe > spinal cord

• CT:

  • hyperattenuating mass with little mass effect

• MR:

  • iso- to hypointense on T1WI + T2WI

  • bright on proton density images

Dysplastic Cerebellar Gangliocytoma

• = Lhermitte-Duclos disease

• Age:	young adults; average age of 34 years
  Associated with:	polydactyly, partial gigantism, leontiasis ossea, vascular malformation
  Strong association with:	Cowden disease (= autosomal dominant hamartoma syndrome characterized by mucocutaneous lesions, macrocephaly, hamartomas and neoplasia of breast, thyroid, colon, genitourinary organs, CNS)

• Path:	disruption of normal cerebellar laminar structure
  Histo:	hypertrophic ganglion cells expanding granular and molecular layers of cerebellar cortex + abnormally increased myelination in molecular layers; marked reduction in myelination of central white matter of cerebellar folia

• symptoms of increased intracranial pressure

• slowly progressive cerebellar syndrome (40%)

• megalencephaly (50%); mental retardation

• CT:

  • hypo- / isoattenuating lesion

  • calcification uncommon

  • thinning of skull

• MR:

  • striated cerebellum sign = laminated / lamellar mass of alternating bands of high + normal signal intensity on T2WI

• Rx:

  decompression of ventricles + resection of mass

Ganglioglioma

• = uncommon slow-growing essentially benign tumor composed of glial + neuronal elements

• Prevalence:	0.4 09.% of all intracranial neoplasms; 1 4% of all pediatric CNS neoplasms
  Peak age:	10 20 years; in 80% <30 years of age; M > F

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• Histo:

  contain ganglion + glial elements: ganglion cells (neurons) arise from primitive neuroblasts + mature during growth; usually astrocytic glial cells predominate in various stages of neoplastic differentiation

• headaches

• medically refractory seizures:

  • Most common cause of chronic temporal lobe epilepsy

• Location:

  frequently above tentorium: in periphery of cerebral hemisphere [temporal (38%) / parietal (30%) / frontal (18%) lobes]; brainstem; cerebellum; pineal region; spinal cord; optic nerve; optic chiasm; ventricles; local involvement of subarachnoid space

• circumscribed slow-growing mass:

  • solid (43%) / cystic (5%) / solid-cystic combination (52%)

• calcifications (30%)

• little associated mass effect / vasogenic edema

• CT:

  • hypoattenuating (38%) / mixed attenuation (32%) / isoattenuating (15%) / hyperattenuating (15%) mass

  • remodeling of skull

  • contrast enhancement (16 80%)

  • Occasionally completely undetectable by CT

• MR:

  • variable (hypo- / isointense) nonspecific MR appearance on T1WI

  • commonly at least one hyperintense region on T2WI

  • nonenhancing / ringlike / homogeneously intense enhancement

• Prognosis:	favorable; malignant degeneration (6%)
  Rx:	gross total resection (with resolution of seizure activity in majority of patients)

Desmoplastic Infantile Ganglioglioma

• = DESMOPLASTIC INFANTILE ASTROCYTOMA = SUPERFICIAL CEREBRAL ASTROCYTOMA ATTACHED TO DURA

• = uncommon variety of ganglioglioma exclusively in infants

• Age:	<18 months (vast majority); M:F = 2:1
  Histo:	spindle cell neoplasm with oval / elongated moderately pleomorphic nuclei + clusters of larger cells with large prominent eccentric nuclei and cytoplasm containing Nissl bodies

• rapidly increasing head circumference

• seizure activity (uncommon)

• Location:

  frontal + parietal > temporal > occipital lobes

• exceptionally large heterogeneously mass:

  • slightly hyperattenuating solid portion typically located along cortical margin

  • cystic components

• intense enhancement of solid component

• CHARACTERISTIC extension of enhancement to leptomeningeal margin (due to firm dural attachment)

• rare vasogenic edema

• NO calcification

• Prognosis:	good
  Rx:	surgical resection

Ganglioneuroma

• = ganglion cells predominate over glial cells

Glioblastoma Multiforme

• Most malignant form of all gliomas / astrocytomas; end stage of progressive severe anaplasia of preexisting Grade I / II astrocytoma (not from embryologic glioblasts)

• Incidence:	most common primary brain tumor; 50% of all intracranial tumors; 1 2% of all malignancies; 20,000 cases per year
  Age:	all ages; peak incidence at 65 75 years;
  	M:F = 3:2; more frequently in whites

• Genetics:	Turcot syndrome, neurofibromatosis type 1, Li-Fraumeni syndrome (familial neoplasms in various organs based on abnormal p53 tumor-suppressor gene)
  Path:	multilobulated appearance; quite extensive vasogenic edema (transudation through structurally abnormal tumor vascular channels); deeply infiltrating neoplasm; hemorrhage; necrosis is essential for pathologic diagnosis (HALLMARK)
  Histo:	highly cellular, often bizarrely pleomorphic / undifferentiated multipolar astrocytes; common mitoses + prominent vascular endothelial proliferation; no capsule; pseudopalisading (= viable neoplastic cells forming an irregular border around necrotic debris as the tumor outgrows its blood supply)
  	Subtypes:
  	(a) giant cell GBM = monstrocellular sarcoma
  	(b) small cell GBM = gliosarcoma = Feigin tumor

• Location:

  • hemispheric: white matter of centrum semiovale: frontal > temporal lobes; common in pons, thalamus, quadrigeminal region; relative sparing of basal ganglia + gray matter

    DDx:

    solitary metastasis, tumefactive demyelinating lesion ( singular sclerosis ), atypical abscess

  • callosal: butterfly glioma may grow exophytically into ventricle

  • posterior fossa: pilocytic astrocytoma, brainstem astrocytoma

  • extraaxial: primary leptomeningeal glioblastomatosis

  • multifocal: in 2 5%

• Spread:

  • direct extension along white matter tracts:

    • corpus callosum (36%), corona radiata, cerebral peduncles, anterior commissure, arcuate fibers

    • readily crosses midline = butterfly glioma (clue: invasion of septum pellucidum)

    • frontal + temporal gliomas tend to invade basal ganglia

    • may invade pia, arachnoid and dura (mimicking meningioma)

  • subependymal carpet after reaching the surface of the ventricles

  • via CSF (<2%)

  • hematogenous (extremely rare)

    • osteoblastic bone lesion

• NECT:

  • inhomogeneous low-density mass with irregular shape + poorly defined margins (hypodense solid tumor / cavitary necrosis / tumor cyst / peritumoral fingers of edema )

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  • considerable mass effect: compression + displacement of ventricles, cisterns, brain parenchyma

  • iso- / hyperdense portions (hemorrhage) in 5%

  • rarely calcifies (if coexistent with lower-grade glioma / after radio- or chemotherapy)

• CECT:

  • Enhancement pattern: contrast enhancement due to breakdown of blood-brain barrier / neovascularity / areas of necrosis

    • diffuse homogeneous enhancement

    • heterogeneous enhancement

    • ring pattern (occasionally enhancing mass within the ring)

    • low-density lesion with contrast-fluid level (leakage of contrast)

  • almost always ring blush of variable thickness: multiscalloped ( garland ), round / ovoid; may be seen surrounding ventricles (subependymal spread); tumor usually extends beyond margins of enhancement

  • sedimentation level secondary to cellular debris / hemorrhage / accumulated contrast material in tumoral cyst

• MR:

  • poorly defined lesion with some mass effect / vasogenic edema / heterogeneity

  • hemosiderin deposits (gradient echo images)

  • hemorrhage (hypointensity on T2WI and T2*WI)

  • T1WI + gadolinium-DTPA enhancement separate tumor nodules from surrounding edema, central necrosis and cyst formation

• Angio:

  • wildly irregular neovascularity + early draining veins

  • avascular lesion

• PET:

  • increase in glucose utilization rate

• Rx:	surgery + radiation therapy + chemotherapy
  Prognosis:	16 18 months postoperative survival (frequent tumor recurrence due to uncertainty during surgery about tumor margins)

Multifocal GBM

• Spread of primary GBM

• Multiple areas of malignant degeneration in diffuse low-grade astrocytoma ( gliomatosis cerebri )

• Inherited / acquired genetic abnormality

Glioma

• = malignant tumors of glial cells growing along white matter tracts, tendency to increase in grade with time; may be multifocal

• Incidence:

  30 40% of all primary intracranial tumors; 50% of solitary supratentorial masses

• contrast enhancement:

  • Increases in proportion to degree of anaplasia

  • Diminished intensity of enhancement with steroid therapy

• CELL OF ORIGIN

  1. Astrocyte	Astrocytoma
  2. Oligodendrocyte	Oligodendroglioma
  3. Ependyma	Ependymoma
  4. Medulloblast	Medulloblastoma;(PNET = primitive neuroectodermal tumor)
  5. Choroid plexus	Choroid plexus papilloma

• FREQUENCY OF INTRACRANIAL GLIOMAS

  Glioblastoma multiforme	51%
  Astrocytoma	25%
  Ependymoma	6%
  Oligodendroglioma	6%
  Spongioblastoma polare	3%
  Mixed gliomas	3%
  Astroblastoma	2%

• Age peak:	middle adult life
  Location:	cerebral hemispheres; spinal cord; brainstem + cerebellum (in children)

Brainstem Glioma

• Incidence:	1%; 12 15% of all pediatric brain tumors; 20 30% of infratentorial brain tumors in children
  Histo:	usually anaplastic astrocytoma / glioblastoma multiforme with infiltration along fiber tracts
  Age:	in children + young adults; peak age 3 13 years; M:F = 1:1

• become clinically apparent early before ventricular obstruction occurs

• ipsilateral progressive multiple cranial nerve palsies

• contralateral hemiparesis

• cerebellar dysfunction: ataxia, nystagmus

• eventually respiratory insufficiency

• Location:	pons > midbrain > medulla; often unilateral at medullopontine junction
  	Medullary + mesencephalic gliomas are more benign than pontine gliomas!

• Growth pattern:

  • diffuse infiltration of brainstem with symmetric expansion + rostrocaudal spread into medulla / thalamus + spread to cerebellum

  • focally exophytic growth into adjacent cisterns (cerebellopontine, prepontine, cisterna magna)

• asymmetrically expanded brainstem

• flattening + posterior displacement of 4th ventricle + aqueduct of Sylvius

• compression of prepontine + interpeduncular cistern (in upward transtentorial herniation)

• paradoxical widening of CP angle cistern with tumor extension into CP angle

• paradoxical anterior displacement of 4th ventricle with tumor extension into cisterna magna

• CT:

  • isodense / hypodense mass with indistinct margins

  • hyperdense foci (= hemorrhage) uncommon

  • absent / minimal / patchy contrast enhancement (50%)

  • ring enhancement in necrotic / cystic tumors (most aggressive)

  • prominent enhancement in exophytic lesion

  • hydrocephalus uncommon (because of early symptomatology)

• MR:

  (better evaluation in subtle cases)

  • hypointense on T1WI + hyperintense on T2WI

  • often only subtle enhancement

  P.290

  
  

  • engulfment of basilar artery

• Angio:

  • anterior displacement of basilar artery + anterior pontomesencephalic vein

  • posterior displacement of precentral cerebellar vein

  • posterior displacement of posterior medullary + supratonsillar segments of PICA

  • lateral displacement of lateral medullary segment of PICA

• Prognosis:	10 30% 5-year survival rate
  Rx:	radiation therapy
  DDx:	focal encephalitis, resolving hematoma, vascular malformation, tuberculoma, infarct, multiple sclerosis, metastasis, lymphoma

Hypothalamic / Chiasmatic Glioma

• Point of origin often undeterminable: hypothalamic gliomas invade chiasm, chiasmatic gliomas invade hypothalamus

• Incidence:	10 15% of supratentorial tumors in children
  Age:	2 4 years; M:F = 1:1
  Associated with:	von Recklinghausen disease (20 50%)

• diminished visual acuity (50%) with optic atrophy

• diencephalic syndrome (in up to 20%): marked emaciation, pallor, unusual alertness, hyperactivity, euphoria

• obese child

• sexual precocity

• diabetes insipidus

• obstructive hydrocephalus

• suprasellar hypodense lobulated mass with dense inhomogeneous enhancement

• hypointense on T1WI + hyperintense on T2WI

• cyst formation, necrosis, calcifications render lesion inhomogeneous

• DDx:

  hypothalamic hamartoma

Globoid Cell Leukodystrophy

• = KRABBE DISEASE

• Cause:	deficiency of galactosylceramide beta-galactosidase resulting in cerebroside accumulation + destruction of oligodendrocytes
  Dx:	biochemical assay from white blood cells / skin fibroblasts
  Age:	3 6 months

• restlessness + irritability

• marked spasticity

• optic atrophy

• hyperacusis

• symmetric hyperdense lesions in thalami, caudate nuclei, corona radiata

• decreased attenuation of white matter

• brain atrophy with enlargement of ventricles

• Prognosis:

  death within first few years of life

Hallervorden-Spatz disease

• = rare familial neurodegenerative metabolic disorder with abnormal iron retention in basal ganglia

• Age:	2nd decade of life
  Histo:	hyperpigmentation + symmetrical destruction of globus pallidus + substantia nigra

• progressive gait impairment + rigidity of limbs

• slowing of voluntary movements, dysarthria

• choreoathetotic movement disorder

• progressive dementia

• CT:

  • low- (= tissue destruction) / high-density (= dystrophic calcification) foci in globus pallidus

• MR:

  • eye-of-the-tiger sign:

    • initially hypointense globus pallidus on T2WI (= iron deposition)

    • later central hyperintense foci on T2WI (= tissue destruction + gliosis)

Hamartoma of CNS

• rare tumor

  • sporadic

  • associated with tuberous sclerosis; may degenerate into giant cell astrocytoma

• Age:	0 30 years
  Location:	temporal lobe, hamartoma of tuber cinereum, subependymal in tuberous sclerosis

• cyst with little mass effect, possibly with focal calcifications

• usually no enhancement

Head Trauma

• = CNS TRAUMA

• Incidence:	0.2 0.3% annually in United States are significant; peak at 550/100,000 people aged 15 24 years; second peak >50 years of age
  Cause:	motor vehicle accidents (51%), fall (21%), assault and violence (12%), sports and recreation (10%)

• Classification:

  • Primary traumatic lesion

    • primary neuronal injury

      • Cortical contusion

      • Diffuse axonal injury

      • Subcortical gray matter injury

        • = injury to thalamus basal ganglia

      • Primary brainstem injury

    • primary hemorrhages (from injury to a cerebral artery / vein / capillary)

      • Subdural hematoma

      • Epidural hematoma

      • Intracerebral hematoma

      • Diffuse hemorrhage (intraventricular, subarachnoid)

    • primary vascular injuries

      • Carotid-cavernous fistula

      • Arterial pseudoaneurysm

        Location:

        branches of ACA + MCA, intra- cavernous portion of ICA, pCom

      • Arterial dissection / laceration / occlusion

      • Dural sinus laceration / occlusion

    • traumatic pia-arachnoid injury

      • Posttraumatic arachnoid cyst

      • Subdural hygroma

    • cranial nerve injury

  • Secondary traumatic lesion

    • deterioration of consciousness / new neurologic signs some time after initial injury

      P.291

      
      

      • 1. Major territorial arterial infarction

        Cause:	prolonged transtentorial / subfalcine herniation pinching the artery against a rigid dural margin
        Location:	PCA, ACA territory

      • 2. Boundary + terminal zone infarction

      • 3. Diffuse hypoxic injury

      • 4. Diffuse brain swelling / edema

      • 5. Pressure necrosis from brain herniation

        Cause:	increased intracranial pressure
        Location:	cingulate, uncal, parahippocampal gyri, cerebellar tonsils

      • 6. Secondary delayed hemorrhage

      • 7. Secondary brainstem injury (mechanical compression, secondary (Duret) hemorrhage in tegmentum of rostral pons + midbrain, infarction of median / paramedian perforating arteries, necrosis)

      • 8. Other (eg, fatty embolism, infection)

      • Duret hemorrhage = hemorrhage in lateral brainstem due to massive temporal lobe herniation

      • Kernahorn notch = contusion of contralateral brainstem caused by pressure of free edge of tentorium

    • Pathomechanism:

      • Direct impact on brain due to fracture / skull distortion

        • scalp / skull abnormal

        • superficial neural damage localized to immediate vicinity of calvarial injury

        • 1. Cortical laceration due to depressed fracture fragment

        • 2. Epidural hematoma

      • Indirect injury irrespective of skull deformation

        • scalp / skull normal

        • (a) compression-rarefaction strain = change in cell volume without change in shape (rare)

        • (b) shear strain = change in shape without change in volume by

          • rotational acceleration forces (more common)

            • bilateral multiple superficial / deep lesions possibly remote from the site of impact

            • 1. Cortical contusion (brain surface)

            • 2. Diffuse axonal injury (white matter)

            • 3. Brainstem + deep gray matter nuclei

          • linear acceleration forces (less common)

            • Subdural hematoma

            • Small superficial contusion

    • Prognosis:

      10% fatal, 5 10% with residual deficits

    • Centripetal approach in search of injury:

      • Scalp

        • Scalp abrasion: not visible

        • Scalp laceration: air inclusion

        • Scalp contusion: salt-and-pepper densities

      • Subgaleal hematoma

        Location:

        between periosteum of outer table and galea (= underneath scalp fat)

    • Skull fracture:

      • linear ~, stellate ~, depressed ~, basilar ~, eggshell ~

    • Epidural hematoma

    • Subdural hematoma

    • Subarachnoid hemorrhage

    • Brain injury

      • Contusion/ edema

      • Brain hematoma

    • Ventricular hemorrhage

• Indications for radiographic skull series:

  • Only in conjunction with positive CT scan findings!

  • 1. Evaluation of depressed skull fracture / fracture of base of the skull

• Indications for CT:

  • Loss of consciousness (more than transient)

  • Altered mental status during observation

  • Focal neurologic signs

  • Clinically suspected basilar fracture

  • Depressed skull fracture (= outer table of fragment below level of inner table of calvarium)

  • Penetrating wound (eg, bullet)

  • Suspected acute subarachnoid hemorrhage, epidural / subdural / parenchymal hematoma

  • CT report must address:

    • midline shift

    • localized mass effect

    • distortion / effacement of basal, perimesencephalic, suprasellar, quadrigeminal cisterns

    • pressure on brainstem, brainstem abnormality

    • hemorrhage / contusion: extraaxial, intraaxial, subarachnoid, intraventricular

    • edema: generalized / localized

    • hydrocephalus

    • presence of foreign bodies, bullet, bone fragments, air

    • base of skull, face, orbit

    • scalp swelling

• Indications for MR:

  • Postconcussive symptomatology

  • Diagnosis of small sub- / epidural hematoma

  • Suspected diffuse axonal (shearing) injury, cortical contusion, primary brainstem injury

  • Vascular damage (eg, pseudoaneurysm formation due to basilar skull fracture)

• Sequelae of head injury:

  • Posttraumatic hydrocephalus (1/3)

    • = obstruction of CSF pathways secondary to intracranial hemorrhage; develops within 3 months

  • Generalized cerebral atrophy (1/3)

    • = result of ischemia + hypoxia

      Glasgow Coma Scale

      Response	Score	Response	Score
      Eye opening		Verbal response
      spontaneous	4	oriented	5
      to voice	3	confused	4
      to pain	2	inappropriate words	3
      none	1	incomprehensible	2
      		none	1
      Motor response
      obeys commands	6	localizes pain	5
      withdraws (pain)	4	flexion (pain)	3
      extension (pain)	2	none	1

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  • Encephalomalacia

    • focal areas of decreased density, but usually higher density than CSF

  • Pseudoporencephaly

    • = CSF-filled space communicating with ventricle / subarachnoid space from cystic degeneration

  • Subdural hygroma

  • Leptomeningeal cyst

    • = progressive protrusion of leptomeninges through traumatic calvarial defect

  • Cerebrospinal fluid leak

    • rhinorrhea, otorrhea (indicating basilar fracture with meningeal tear)

  • Posttraumatic abscess

    • secondary to (a) penetrating injury (b) basilar skull fracture (c) infection of traumatic hematoma

  • Parenchymal injury

    • brain atrophy, residual hemoglobin degradation products, wallerian-type axonal degeneration, demyelination, cavitation, microglial scarring

  • Prognosis:	up to 10% fatal; 5 10% with some degree of neurologic deficit
    Mortality:	25/100,000 per year (traffic-related in 20 50%, gunshot 20 40%; falls)

Extracerebral Hemorrhage

• Subdural hematoma

  in adults:

  dura inseparable from skull

• Epidural hematoma

  in children:

  dura easily stripped away from skull

• Subarachnoid hemorrhage

  • common accompaniment to severe cerebral trauma

Intracerebral Hemorrhage

• Hematoma

  • = blood separating relatively normal neurons

    • shear-strain injury (most common)

    • blunt / penetrating trauma (bullet, ice pick, skull fracture fragment)

  • Incidence:	2 16% of trauma victims
    Location:	low frontal + anterior temporal white matter / basal ganglia (80 90%)

  • frequently no loss of consciousness

  • development may be delayed in 8% of head injuries

  • well-defined homogeneously increased density

• Cortical contusion

  • = blood mixed with edematous brain

  • poorly defined area of mixed high and low densities, may increase with time

• Intraventricular hemorrhage

  • = potential complication of any intracranial hemorrhage

  • For earliest detection focus on occipital horns!

Other Posttraumatic Lesions

• Pneumocephalus

• Penetrating foreign body

Hemangioblastoma of CNS

• = benign autosomal dominant tumor of vascular origin

• Incidence:	1 2.5% of all intracranial neoplasms; most common primary infratentorial neoplasm in adults (10% of posterior fossa tumors)
  Age:	(a) adulthood (>80%): 20 50 years, average age of 33 years; M > F
  	(b) childhood (<20%): in von Hippel-Lindau disease (10 20%); girls

• Associated with:

  • von Hippel-Lindau disease (in 20%), may have multiple hemangioblastomas (only 20% of patients show other stigmata)

  • pheochromocytoma (often familial)

  • syringomyelia

  • spinal cord hemangioblastomas

• ; headaches, ataxia, nausea, vomiting

• erythrocythemia in 20% (tumor elaborates stimulant)

• Location: paravermian cerebellar hemisphere (85%) > spinal cord > cerebral hemisphere / brainstem; multiple lesions in 10%

• solid (1/3) / cystic / cystic + mural nodule

• solid portion often intensely hemorrhagic

• almost never calcifies

• CT:

  • cystic sharply marginated mass of CSF-density (2/3)

  • peripheral mural nodule with homogeneous enhancement (50%)

  • occasionally solid with intense homogeneous enhancement

• MR:

  • well-demarcated tumor mass moderately hypointense on T1WI + T2WI

  • hyperintense areas on T1WI (= hemorrhage)

  • hypointense areas on T1WI + hyperintense areas on T2WI (= cyst formation)

  • intralesional vermiform areas of signal dropout

  • (= high-velocity blood flow)

  • heterogeneous enhancement on Gd-DTPA with nonenhancing foci of cyst formation + calcification + rapidly flowing blood

  • perilesional Gd-DTPA enhancing areas of slow-flowing blood vessels feeding + draining the tumor

  • peripheral hyperintense rim on T2WI (= edema)

• Angio:

  • densely stained tumor nidus within cyst ( contrast loading )

  • staining of entire rim of cyst

  • draining vein

• Prognosis:	>85% postsurgical 5-year survival rate
  DDx:	(1) Cystic astrocytoma (>5 cm, calcifications, larger nodule, thick-walled lesion, no angiographic contrast blush of mural nodule, no erythrocythemia)
  	(2) Arachnoid cyst (if mural nodule not visualized)
  	(3) Metastasis (more surrounding edema)

Hematoma of Brain

• = INTRACEREBRAL HEMATOMA

• Etiology:

  • Very common

    • Chronic hypertension (50%)

    • Age: >60 years

  • Location:

    external capsule and basal ganglia (putamen in 65%) / thalamus (25%), pons (5%) + brainstem (10%), cerebellum (5%), cerebral hemisphere (5%)

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  • Trauma

  • Aneurysm

  • Vascular malformation: AVM, cavernous hemangioma, venous angioma, capillary telangiectasia

• Common

  • Hemorrhagic infarction = hemorrhagic transformation of stroke

  • Amyloid angiopathy (20%): elderly patients

  • Coagulopathy (5%): DIC, hemophilia, idiopathic thrombocytopenic purpura; aspirin, heparin, coumadin

  • Drug abuse (5%): amphetamines, cocaine, heroine

  • Bleeding into tumor

    • primary: GBM, ependymoma, oligodendroglioma, pituitary adenoma

    • metastatic: melanoma, choriocarcinoma, renal cancer, thyroid cancer, adenocarcinoma

• Uncommon

  • Venous infarction

  • Eclampsia

  • Septic emboli

  • Vasculitis (especially fungal)

  • Encephalitis

Stages of Cerebral Hematomas

• Progression:	hematoma gradually snowballs in size, dissects along white matter tracts; may decompress into ventricular system / subarachnoid space
  Resolution:	resorption from outside toward the center; rate depends on size of hematoma (usually 1 6 weeks)

• FALSE-NEGATIVE CT:

  • impaired clotting

  • anemia

  • iso- / hypodense stage

Hyperacute Cerebral Hemorrhage

• Time period:	4 6 hours
  Substrate:	fresh oxygenated arterial blood contains 95% diamagnetic (= no unpaired electrons) intracellular oxyhemoglobin (Fe2+) with higher water contents than white matter; oxyhemoglobin persists for 6 12 hours)

• NCCT:

  • homogeneous consolidated high-density lesion (50 70 HU) with irregular well-defined margins increasing in density during day 1 3 (hematoma attenuation dependent on hemoglobin concentration + rate of clot retraction)

  • usually surrounded by low attenuation (edema, contusion) appearing within 24 48 hours

    • irregular shape in trauma

    • spherical + solitary in spontaneous hemorrhage

  • less mass effect compared with neoplasms

• MR (less sensitive than CT during first hours):

  • little difference to normal brain parenchyma = center of hematoma iso- to hypointense on T1WI + minimally hyperintense on T2WI

  • peripheral rim of hypointensity (= degraded blood products as clue for presence of hemorrhage)

Acute Cerebral Hematoma

• Time period:	12 48 hours
  Substrate:	paramagnetic (= 4 unpaired electrons) intracellular deoxyhemoglobin (Fe2+); deoxyhemoglobin persists for 3 days

• MR:

  • slightly hypo- / isointense on T1WI (= paramagnetic deoxyhemoglobin within clotted intact hypoxic RBCs does not cause T1 shortening)

  • very hypointense on T2WI (progressive concentration of RBCs, blood clot retraction, and fibrin production shorten T2)

  • surrounding tissue isointense on T1WI / hyperintense on T2WI (edema)

Early Subacute Cerebral Hematoma

• Time period:	3 7 days
  Substrate:	intracellular strongly paramagnetic (= 5 unpaired electrons) methemoglobin (Fe3+) inhomogeneously distributed within cells

• NCCT:

  • increase in size of hemorrhagic area over days / weeks

  • high-density lesion within 1st week; often with layering

• MR:

  • very hyperintense on T1WI (= oxidation of deoxyhemoglobin to methemoglobin results in marked shortening of T1)

    • beginning peripherally in parenchymal hematomas

    • beginning centrally in partially thrombosed aneurysm (oxygen tension higher in lumen)

  • DDx:

    melanin, high-protein concentration, flow-related enhancement, gadolinium-based contrast agent

  • very hypointense on T2WI (= intracellular methemoglobin causes T2 shortening)

Late Subacute Cerebral Hematoma

• Time period:	>1 week
  Substrate:	extracellular strongly paramagnetic met-hemoglobin (homogeneously distributed)

• NCCT:

  • gradual decrease in density from periphery inward (1 2 HU per day) during 2nd + 3rd week

• CECT:

  • peripheral rim enhancement at inner border of perilesional lucency (1 6 weeks after injury) in 80% (secondary to blood-brain barrier breakdown / luxury perfusion / formation of hypervascular granulation tissue)

  • ring blush may be diminished by administration of corticosteroids

• MR:

  • hyperintense on T1WI (= RBC lysis allows free passage of water molecules across cell membrane)

  P.294

  
  

  • hyperintense on T2WI (= compartmentalization of methemoglobin is lost due to RBC lysis)

  • surrounding edema isointense on T1WI + hyperintense on T2WI

Chronic Cerebral Hematoma

• Time period:	>1 months
  Substrate:	superparamagnetic ferritin (= soluble + stored in intracellular compartment) and hemosiderin (= insoluble + stored in lysosomes) cause marked field inhomogeneities

• NCCT:

  • isodense hematoma from 3rd 10th week with perilesional ring of lucency

    

    T1 and T2 Signal Changes in Evolution of Intracerebral Hematoma

• CT:

  • hypodense phase (4 6 weeks) secondary to fluid uptake by osmosis

  • decreased density (3 6 months) / invisible

  • after 10 weeks lucent hematoma (encephalomalacia due to proteolysis and phagocytosis + surrounding atrophy) with ring blush (DDx: tumor)

• MR:

  • rim slightly hypointense on T1WI + very hypointense on T2WI (= superparamagnetic hemosiderin + ferritin within macrophages); rim gradually increases over weeks in thickness, eventually fills in entire hematoma = HALLMARK

  P.295

  
  

  • center hyperintense on T1WI + T2WI (= extracellular methemoglobin of lysed RBCs just inside the darker hemosiderin ring); present for months to 1 year

  • surrounding hyperintensity on T2WI (= edema + serum extruded from clot) with associated mass effect should resorb within 4 6 weeks (DDx: malignant hemorrhage)

• Prognosis:

  • herniation (if 3 4 cm in size)

  • death (if >5 cm in size)

Basal Ganglia Hematoma

• = rupture of small distal microaneurysms in the lenticulostriate arteries in patients with poorly controlled systemic arterial hypertension

• Cx:	(1) Dissection into adjacent ventricles (2/3)
  	(2)Porencephaly
  	(3) Atrophy with ipsilateral ventricular dilatation

Heterotopic Gray Matter

• = collection of cortical neurons in an abnormal location secondary to arrest of migrating neuroblasts from ventricular walls to brain surface between 7 24 weeks of GA

• Frequency:	3% of healthy population
  May be associated with:	agenesis of corpus callosum, aqueductal stenosis, microcephaly, schizencephaly

• seizures

• Location:

  • nodular form: usually symmetric bilaterally in subependymal region / periventricular white matter with predilection for posterior + anterior horns

  • laminar form: deep / subcortical regions within white matter (less common)

• single / multiple bilateral subependymal nodules along lateral ventricles

• NO surrounding edema, isointense with gray matter on all sequences, no contrast enhancement

• DDx:

  subependymal spread of neoplasm, subependymal hemorrhage, vascular malformation, tuberous sclerosis, intraventricular meningioma, neurofibromatosis

Holoprosencephaly

• = lack of cleavage / diverticulation of the forebrain (= prosencephalon) laterally (cerebral hemispheres), transversely (telencephalon, diencephalon), horizontally (optic + olfactory structures) as a consequence of arrested lateral ventricular growth in 6-week embryo; cortical brain tissue develops to cover the monoventricle and fuses in the midline; posterior part of the monoventricle becomes enlarged and saclike

• Septum pellucidum always absent!

• Incidence:

  1:16,000; M:F = 1:1

• A. ALOBAR	= no hemispheric development
  B. SEMILOBAR	= some hemispheric development
  C. LOBAR	= frontal and temporal lobation + small monoventricle

• Associated with:	polyhydramnios (60%), renal + cardiac anomalies; chromosomal anomalies (predominantly trisomy 13 + 18)
  	Associated borderline syndromes secondary to diencephalic malformation: Anophthalmia Microphthalmia Aplasia of pituitary gland olfactogenital dysplasia Septo-optic dysplasia

• DDx:

  • Severe hydrocephalus (roughly symmetrically thinned cortex)

  • Dandy-Walker cyst (normal supratentorial ventricular system)

  • Hydranencephaly (frontal + parietal cortex most severely affected)

  • Agenesis of corpus callosum with midline cyst (lateral ventricles widely separated with pointed superolateral margin)

Alobar Holoprosencephaly

• = extreme form in which the prosencephalon does not divide

• minimal motor activity, little sensory response (ineffective brain function); seizures

• severe facial anomalies ( the face predicts the brain ):

  • Normal face in 17%

  • Cyclopia (= midline single orbit); may have proboscis (= fleshy supraorbital prominence) + absent nose

  • Ethmocephaly = 2 hypoteloric orbits + proboscis between eyes and absence of nasal structures

  • Cebocephaly = 2 hypoteloric orbits + single nostril with small flattened nose + absent nasal septum

  • Median cleft lip + cleft palate + hypotelorism

  • Others: micrognathia, trigonocephaly (early closure of metopic suture), microphthalmia, microcephaly

• thalami fused

• protrusion of anteriorly placed fused thalami + basal ganglia into monoventricle

• absence of: septum pellucidum, 3rd ventricle, falx cerebri, interhemispheric fissure, corpus callosum, fornix, optic tracts, olfactory bulb (= arrhinencephaly), internal cerebral veins, superior + inferior straight sagittal sinus, vein of Galen, tentorium, sylvian fissure, opercular cortex

• crescent-shaped holoventricle = single large ventricle without occipital or temporal horns

• large dorsal cyst occupying most of calvarium + widely communicating with single ventricle

• horseshoe / boomerang configuration of brain = peripheral rim of cerebral cortex displaced rostrally (coronal plane)

  • pancake configuration = cortex covers monoventricle to edge of dorsal cyst

  • cup configuration = more cortex visible posteriorly

    

    Ventricular Configuration in Alobar Holoprosencephaly

  P.296

  
  

  • ball configuration = complete covering of monoventricle without dorsal cyst

• midbrain, brainstem, cerebellum structurally normal

• pancakelike cerebrum in posterior cranium

• cerebral mantle pachygyric

• midline clefts in maxilla + palate

• Prognosis:	death within 1st year of life / stillborn
  DDx:	massive hydrocephalus, hydranencephaly

Semilobar Holoprosencephaly

• = intermediate form with incomplete cleavage of prosencephalon (more midline differentiation + beginning of sagittal separation)

• mild facial anomalies: midline cleft lip + palate

• hypotelorism

• mental retardation

• single ventricular chamber with partially formed occipital horns + rudimentary temporal horns

• peripheral rim of brain tissue is several cm thick

• partially fused thalami anteriorly situated + abnormally rotated resulting in small 3rd ventricle

• absence of septum pellucidum + corpus callosum + olfactory bulb

• rudimentary falx cerebri + interhemispheric fissure form caudally with partial separation of occipital lobes

• incomplete hippocampal formation

• Prognosis:

  infants survive frequently into adulthood

Lobar Holoprosencephaly

• = mildest form with two cerebral hemispheres + two distinct lateral ventricles

• May be part of septo-optic dysplasia!

• usually not associated with facial anomalies except for hypotelorism

• mild to severe mental retardation, spasticity, athetoid movements

• closely apposed bodies of lateral ventricles with distinct occipital + frontal horns

• mild dilatation of lateral ventricles

• colpocephaly

• unseparated frontal horns of angular squared shape + flat roof (on coronal images) due to dysplastic frontal lobes

• dysplastic anterior falx + interhemispheric fissure

• absence of septum pellucidum + sylvian fissures

• corpus callosum usually present

• hippocampal formation nearly normal

• basal ganglia + thalami may be fused / separated

• pachygyria (= abnormally wide + plump gyri), lissencephaly (= smooth gyri)

• Prognosis:

  survival into adulthood

Hydatid Disease of Brain

• = canine tapeworm (Echinococcus granulosus) in sheep-and cattle-grazing areas

• Location:

  liver (60%), lung (25%), CNS (2%) subcortical

• usually single, large round, sharply marginated smooth-walled hypodense cyst

• no significant surrounding edema; no rim enhancement

• development of daughter cysts (after rupture / following diagnostic puncture)

Hydranencephaly

• = liquefaction necrosis of cerebral hemispheres replaced by a thin membranous sac of leptomeninges in outer layer + remnants of cortex and white matter in inner layer, filled with CSF + necrotic debris

• Incidence:	0.2% of infant autopsies
  Etiology:	absence of supraclinoid ICA system (? vascular occlusion / infection with toxoplasmosis or CMV) = ultimate form of porencephaly

• seizures; respiratory failure; generalized flaccidity

• decerebrate state with vegetative existence

• normal skull size / macrocrania / microcrania

• complete filling of hemicranium with membranous sac

• absence of cortical mantle (inferomedial aspect of temporal lobe, inferior aspect of frontal lobe, occipital lobe may be identified in some patients)

• brainstem usually atrophic

• cerebellum almost always intact

• thalamic, hypothalamic, mesencephalic structures usually preserved + project into cystic cavity

• central brain tissue can be asymmetric

• choroid plexus present

• falx cerebri + tentorium cerebelli usually intact, may be deviated in asymmetric involvement, may be incomplete / absent

• Prognosis:	not compatible with prolonged extrauterine life (no intellectual improvement from shunting)
  DDx:	(1) Severe hydrocephalus (some identifiable cortex present)
  	(2) Alobar holoprosencephaly (facial midline anomalies)
  	(3) Schizencephaly (some spared cortical mantle)

Hydrocephalus

• = excess of CSF due to imbalance of CSF formation + absorption resulting in increased intraventricular pressure

• Pathophysiology:

  • Overproduction (rare)

  • Impaired absorption

    • Blockage of CSF flow within ventricular system, cisterna magna, basilar cisterns, cerebral convexities

    • Blockage of arachnoid villi / lymphatic channels of cranial nerves, spinal nerves, adventitia of cerebral vessels

• Skull film: signs of raised intracranial pressure

  • YOUNG INFANT / NEWBORN

    • increase in craniofacial ratio

    • bulging of anterior fontanel

    • sutural diastasis

    • macrocephaly + frontal bossing

    • beaten brass = hammered silver appearance = prominent digital impressions (wide range of normals in 4 10 years of age)

  • ADOLESCENT / ADULT (changes in sella turcica)

    • atrophy of anterior wall of dorsum sellae

    • shortening of the dorsum sellae producing pointed appearance

    • erosion / thinning / discontinuity of floor of sella

    • depression of floor of sella with bulging into sphenoid sinus

    • enlargement of sella turcica

    P.297

    
    

    • DDx:

      osteoporotic sella (aging, excessive steroid hormone)

  • Signs favoring hydrocephalus over white matter atrophy:

    • commensurate dilatation of temporal horn with lateral ventricles (most reliable sign)

    • narrowing of ventricular angle (= angle between anterior / superior margins of frontal horns at level of foramen of Monro) due to concentric enlargement:

    • Mickey Mouse ears on axial scans

    • enlargement of frontal horn radius (= widest diameter of frontal horns taken at 90 angle to long axis of frontal horn):

    • rounding of frontal horn shape

    • enlargement of ventricular system disproportionate to enlargement of cortical sulci (due to compression of brain tissue against skull + consequent sulcal narrowing)

    • interstitial edema from transependymal flow of CSF:

      • periventricular hypodensity

      • rim of prolonged T1 + T2 relaxation times surrounding lateral ventricles

    • hydrocephalic distortion of ventricles + brain:

      • atrial diverticulum = herniation of ventricular wall through choroidal fissure of ventricular trigone into supracerebellar + quadrigeminal cisterns

      • dilatation of suprapineal recess expanding into posterior incisural space resulting in inferior displacement of pineal gland / shortening of tectum in rostral-caudal direction / elevation of vein of Galen

      • enlargement of anterior recess of 3rd ventricle extending into suprasellar cistern

Compensated hydrocephalus

• = new equilibrium established at higher intracranial pressure due to opening of alternate pathways (arachnoid membrane / stroma of choroid plexus / extracellular space of cortical mantle = transependymal flow of CSF)

Obstructive Hydrocephalus

• = obstruction to normal CSF flow + absorption

Communicating Hydrocephalus

• = EXTRAVENTRICULAR HYDROCEPHALUS

• = elevated intraventricular pressure secondary to blockade beyond the outlet of 4th ventricle within the subarachnoid pathways

• Incidence:

  38% of congenital hydrocephaly

• Pathophysiology:

  • unimpeded CSF flow through ventricles; impeded CSF flow over convexities by adhesions / impeded reabsorption by arachnoid villi

• Cause:

  • repetitive subarachnoid microhemorrhage (most common cause), immaturity of arachnoid villi, meningeal carcinomatosis (medulloblastoma, germinoma, leukemia, lymphoma, adenocarcinoma), purulent / tuberculous meningitis, subdural hematoma, craniosynostosis, achondroplasia, Hurler syndrome, venous obstruction (obliteration of superior sagittal sinus), absence of Pacchioni granulations

  • symmetric enlargement of lateral, 3rd, and often 4th ventricles

  • dilatation of subarachnoid cisterns

  • normal / effaced cerebral sulci

  • symmetric low attenuation of periventricular white matter (transependymal CSF flow)

  • delayed ascent of radionuclide tracer over convexities

  • persistence of radionuclide tracer in lateral ventricles for up to 48 hours

• Changes after successful shunting:

  • diminished size of ventricles + increased prominence of sulci

  • cranial vault may thicken

  • Cx:

    subdural hematoma (result from precipitous decompression)

Noncommunicating Hydrocephalus

• = INTRAVENTRICULAR HYDROCEPHALUS

• = blockade of CNS flow within the ventricular system with dilatation of ventricles proximal to obstruction

• Pathogenesis:

  • increased CSF pressure causes ependymal flattening with breakdown of CSF-brain barrier leading to myelin destruction + compression of cerebral mantle (brain damage)

• Location:

  • Lateral ventricular obstruction

    Cause:

    ependymoma, intraventricular glioma, meningioma

  • Foramen of Monro obstruction

    Cause:

    3rd ventricular colloid cyst, tuber, papilloma, meningioma, septum pellucidum cyst / glioma, fibrous membrane (post infection), giant cell astrocytoma

  • Third ventricular obstruction

    Cause:

    large pituitary adenoma, teratoma, craniopharyngioma, glioma of 3rd ventricle, hypothalamic glioma

  • Aqueductal obstruction

    Cause:

    Congenital web / atresia (often associated with Chiari malformation), fenestrated aqueduct, tumor of mesencephalon / pineal gland, tentorial meningioma, S/P intra-ventricular hemorrhage or infection

  • Fourth ventricular obstruction

    Cause:

    Congenital obstruction, Chiari malformation, Dandy-Walker syndrome, inflammation (TB), tumor within 4th ventricle (ependymoma), extrinsic compression of 4th ventricle (astrocytoma, medulloblastoma, large CPA tumors, posterior fossa mass), isolated / trapped 4th ventricle

• enlarged lateral ventricles (enlargement of occipital horns precedes enlargement of frontal horns)

• effaced cerebral sulci

• periventricular edema with indistinct margins (especially frontal horns)

• radioisotope cisternography: no obstruction if tracer reaches ventricle

• change in RI indicates increased intracranial pressure ( RI 47 132% versus 3 29% in normals)

P.298

Nonobstructive Hydrocephalus

• = secondary to rapid CSF production

  Cause:

  Choroid plexus papilloma

  • ventricle near papilloma enlarges

  • intense radionuclide uptake in papilloma

  • enlarged anterior / posterior choroidal artery and blush

Congenital Hydrocephalus

• = multifactorial CNS malformation during the 3rd / 4th week after conception

• Etiology:

  • aqueductal stenosis (43%)

  • communicating hydrocephalus (38%)

  • Dandy-Walker syndrome (13%)

  • other anatomic lesions (6%)

    • Genetic factors: spina bifida, aqueductal stenosis (X-linked recessive trait with a 50% recurrence rate for male fetuses), congenital atresia of foramina of Luschka and Magendie (Dandy-Walker syndrome; autosomal recessive trait with 25% recurrence rate), cerebellar agenesis, cloverleaf skull, trisomy 13 18

    • Nongenetic etiology: tumor compressing 3rd / 4th ventricle, obliteration of subarachnoid pathway due to infection (syphilis, CMV, rubella, toxoplasmosis), proliferation of fibrous tissue (Hurler syndrome), Chiari malformations, vein of Galen aneurysm, choroid plexus papilloma, vitamin A intoxication

  Incidence:

  0.3 1.8:1,000 pregnancies

• Associated with:

  • Intracranial anomalies (37%): hypoplasia of corpus callosum, encephalocele, arachnoid cyst, arteriovenous malformation

  • extracranial anomalies (63%): spina bifida in 25 30% (with spina bifida hydrocephalus is present in 80%), renal agenesis, multicystic dysplastic kidney, VSD, tetralogy of Fallot, anal agenesis, malrotation of bowel, cleft lip / palate, Meckel syndrome, gonadal dysgenesis, arthrogryposis, sirenomelia

  • chromosomal anomalies (11%): trisomy 18 + 21, mosaicism, balanced translocation

• elevated amniotic alpha-fetoprotein level

• OB-US (assessment difficult prior to 20 weeks GA as ventricles ordinarily constitute a large portion of cranial vault):

  • dangling choroid plexus sign :

    • choroid plexus not touching medial + lateral walls of lateral ventricles

    • downside choroid plexus falling away from medial wall + hanging from tela choroidea

    • upside choroid falling away from lateral wall

  • lateral width of ventricular atrium 10 mm (size usually constant between 16 weeks MA and term)

    • 88% of fetuses with sonographically detected neural axis anomalies have atrial width >10 mm

  • BPD >95th percentile (usually not before 3rd trimester)

  • polyhydramnios (in 30%)

• Recurrence rate:	<4%
  Mortality:	(1) fetal death in 24%
  	(2) neonatal death in 17%
  Prognosis:	poor with
  	(1) associated anomalies
  	(2) shift of midline (porencephaly)
  	(3) head circumference >50 cm
  	(4) absence of cortex (hydranencephaly)
  	(5) cortical thickness <10 mm

Infantile Hydrocephalus

• ocular disturbances: paralysis of upward gaze, abducens nerve paresis, nystagmus, ptosis, diminished pupillary light response

• spasticity of lower extremities (from disproportionate stretching of paracentral corticospinal fibers)

• Etiology:

  • mnemonic: A VP-Shunt Can Decompress The Hydrocephalic Child

    • Aqueductal stenosis

    • Vein of Galen aneurysm

    • Postinfectious

    • Superior vena cava obstruction

    • Chiari II malformation

    • Dandy-Walker syndrome

    • Tumor

    • Hemorrhage

    • Choroid plexus papilloma

• Doppler:

  • RI >0.8 (sign of increased ICP) in neonate:

  • RI of 0.84 13% decreasing to 0.72 11% after shunting

  • RI >0.65 (sign of increased ICP) in older children

Normal Pressure Hydrocephalus

• = NPH = ADAM SYNDROME

• = pressure gradient between ventricle + brain parenchyma in spite of normal CSF pressure

• Potentially treatable cause of dementia in elderly!

• Cause:	communicating hydrocephalus with incomplete arachnoidal obstruction from neonatal intraventricular hemorrhage, spontaneous subarachnoid hemorrhage, intracranial trauma, infection, surgery, carcinomatosis
  	mnemonic:	PAM the HAM
  	Paget disease
  	Aneurysm
  	Meningitis
  	Hemorrhage (from trauma)
  	Achondroplasia
  	Mucopolysaccharidosis

• Pathophysiology of CSF:

  • (?) brain pushed toward cranium from ventricular enlargement; brain unable to expand during systole thus compressing lateral + 3rd ventricles + expressing large CSF volume through aqueduct; reverse dynamic during diastole; water-hammer force of recurrent ventricular expansion damages periventricular tissues

• Age:

  50 70 years

• normal opening pressure at lumbar puncture

• dementia, gait apraxia, urinary incontinence

• mnemonic:

  wacky, wobbly and wet

• communicating hydrocephalus with prominent temporal horns

P.299




• ventricles dilated out of proportion to any sulcal enlargement

• upward bowing of corpus callosum

• flattening of cortical gyri against inner table of calvarium (DDx: rounded gyri in generalized atrophy)

• MR:

  • pronounced aqueductal flow void (due to diminished compliance of normal pressure hydrocephalus)

  • periventricular hyperintensity (due to transependymal CSF flow)

• Rx:

  CSF shunting (only 50% improved)

Hypothalamic Hamartoma

• = HAMARTOMA OF TUBER CINEREUM

• = rare congenital malformation composed of normal neuronal tissue arising from posterior hypothalamus in region of tuber cinereum

• Age:	<2 years of age; M > F
  Histo:	heterotopic collection of neurons, astrocytes, oligodendroglial cells (closely resembling histologic pattern of tuber cinereum)

• isosexual precocious puberty (due to LRH secretion)

• gelastic seizures, hyperactivity

• neurodevelopmental delay

• Location:

  mamillary bodies / tuber cinereum of thalamus, rarely within hypothalamus itself

• well-defined round / oval mass projecting from base of brain into suprasellar / interpeduncular cistern

• attached to tuber cinereum / mamillary bodies by thin stalk (pedunculated)

• remain stable in size over time; up to 4 cm in diameter

• CT:

  • round homogeneous mass isodense with brain tissue

  • NO enhancement

• MR:

  • well-defined round pedunculated mass suspended from tuber cinereum / mamillary bodies

  • isointense on T1WI + iso- / slightly hyperintense on T2WI (imaging characteristics of gray matter)

  • no gadolinium enhancement

Idiopathic Intracranial Hypertension

• = PSEUDOTUMOR CEREBRI = BENIGN INTRACRANIAL HYPERTENSION (BIH)

• secondary to

  • elevation in blood volume (85%)

  • decrease in regional cerebral blood flow with delayed CSF absorption (10%)

• Etiology:

  • Sinovenous occlusive disease, SVC occlusion, obstruction of dural sinus, obstruction of both internal jugular veins

  • Dural AVM

  • S/P brain biopsy with edema

  • Endocrinopathies

  • Hypervitaminosis A

  • Hypocalcemia

  • Menstrual dysfunction, pregnancy, menarche, birth control pills

  • Drug therapy

• Predilection for:

  obese young to middle-aged women

• headache

• papilledema

• elevated opening pressures on lumbar puncture (normal range of 80-180 mm H₂O in horizontal lateral decubitus position)

• normal ventricular size / pinched ventricles

• increased volume of subarachnoid space

Infarction of Brain

• = brain cell death leading to coagulation necrosis

• Cause:	large vessel occlusion of ICA / MCA / PCA (50%) due to emboli from atherosclerotic stenosis, small-vessel lacunes (25%), cardiac cause (15%), blood disorder (5%), non-arteriosclerotic (5%)
  	33% of TIAs will lead to infarction!

• Pathophysiology:

  • distal microstasis occurs within 2 minutes after occlusion of cerebral artery; regional cerebral blood flow is acutely decreased in area of infarction + remains depressed for several days at center of infarct; arterial circulation time may be prolonged in entire hemisphere; rapid development of vasodilatation due to hypoxia, hypercapnia, tissue acidosis; delayed filling + emptying of arterial channels in area of infarction (= arteriolar-capillary block) well into venous phase; by end of 1st week regional blood flow commonly increases to rates even above those required for metabolic needs (= hyperemic phase = luxury perfusion)

• stroke

  • DDx:

    intracerebral hemorrhage, subdural hematoma, cerebritis, hemiplegic / hemisensory migraine, tumor, arteriovenous malformation

• Detection rate by CT:

  • 80% for cortex + mantle, 55% for basal ganglia, 54% for posterior fossa

  • Positive correlation between degree of clinical deficit and CT sensitivity

  • CT sensitivity:

    on day of ictus:	48%
    1 2 days later:	59%
    7 10 days later:	66%
    10 11 days later:	74%

• Location:

  cerebrum:cerebellum = 19:1

  • supratentorial

    • cerebral mantle (70%) in territory of MCA (50%), PCA (10%), watershed between MCA + ACA (7%), ACA (4%)

    • basal ganglia + internal capsule (20%)

  • infratentorial (10%)

    • upper cerebellum (5%), lower cerebellum (3%), pons + medulla (2%)

Hyperacute Ischemic Infarction

• Time period:

  <12 hours

• CT (relatively insensitive + nonspecific):

  • normal (in 10 60%)

  • subtle decrease in attenuation within affected brain area:

    • hypoattenuating appearance of gray matter:

      • insular ribbon sign = obscuration of lentiform nucleus due to decreased attenuation within insula (in 50 80% of MCA occlusions)

      P.300

      
      

      • hypoattenuation of basal ganglia becoming isodense to internal + external capsule

    • loss of gray-white matter differentiation

  • mass effect from brain swelling:

    • hemispheric sulcal effacement / compression

    • narrowing of sylvian fissure (in MCA infarct)

  • hyperdense middle cerebral artery sign = acute intraluminal thrombus of 80 HU (due to extrusion of serum from thrombus) vs. 40 HU of flowing blood; transient phenomenon

    Incidence:	35 50% of acute MCA occlusions
    DDx:	high hematocrit level in normal arteries, calcification of vessel wall

  • calcified intraluminal embolus (rare)

• MR (routinely positive by 4 6 hours post ictus):

  • hyperintense signal on proton-density images + T2WI involving cortical gray matter

  • loss of normal intravascular flow voids (similar to hyperdense MCA sign)

  • stasis of contrast material within affected arteries due to stasis of flow distal to thrombus

  • loss of gray-white matter distinction on T2WI

  • subtle parenchymal swelling with sulcal effacement due to cytotoxic edema (= increased intracellular water) can be seen by 2 hours post ictus (best on T1WI)

  • hyperintense signal from less signal loss (due to restricted water diffusibility) on diffusion-weighted images (MOST SENSITIVE, hyperintensity maintained for 7 10 days, which allows discrimination of acute from older infarcts)

  • ischemic penumbra = combination of perfusion + diffusion-weighted images allows identification of areas at risk for infarction

• NUC:

  • Newer imaging agents (eg, Tc-99m HM-PAO) may be positive within minutes of the event, while CT and MR are normal

  • hemispheric hypoperfusion throughout all phases

  • defect corresponding to nonperfused vascular territory

  • flip-flop sign in radionuclide angiogram (15%) = decreased uptake during arterial + capillary phase followed by increased uptake during venous phase

  • luxury perfusion syndrome (14%) = increased perfusion

• Rx:

  recombinant tissue plasminogen activator (tPA) if symptom onset <3 hours ago

Acute Ischemic Infarction

• Histo:

  cortical cytotoxic edema (= accumulation of intracellular water due to cell membrane damage) followed by white matter vasogenic edema

• bright lesion on DWI very conspicuous within 0 6 hours after onset of symptoms + up to 14 days after ictus (diffusion coefficient is a measure of proton mobility in tissue

• * a low coefficient (acute infarct) gives a hyperintense signal

• * a high coefficient (CSF) gives a hypointense signal)

• false positive DWI:

  • diffusion coefficient of infarcts is influenced by T2 properties + b-value of gradient strength (T2 shine-through)

• 5% false negative DWI

• hypointense signal on ADC map (negating T2 shine-through effect) within 24 hours

• (ADC map shows pure diffusion characteristics without T2 effect, but has low lesion conspicuity)

  • a low coefficient (acute infarct) gives a hypointense signal

  • a high coefficient (CSF) gives a hyperintense signal)

Early Acute Ischemic Infarction

• Time period:

  12 24 hours

• NCCT:

  • low-density lesion (30 60% invisible)

  • loss of differentiation between cortical gray matter and subjacent white matter:

    • blurring of the clarity of internal capsule

    • insular ribbon sign = hypodense extreme capsule no longer distinguishable from insular cortex

  • subtle sulcal effacement (8%)

• CECT:

  • no iodine accumulation in affected cortical region

  • meningeal gyriform enhancement

• MR:

  • subtle narrowing of sulci

  • blurring of gray-white matter junction on T2- and proton-density images

  • increase in thickness of cortex (= gyral swelling)

  • subtle low-signal intensity on T1WI, high-signal intensity on T2WI (masking of gyral infarcts on heavily T2WI due to sulcal CSF intensity)

  • 20 30% false negative T2WI during first 24 hours

• MRA:

  • absence of flow for infarcts >2 cm in diameter

Late Acute Ischemic Infarction

• Time period:

  1 3 7 days

• NCCT:

  • hypodense wedge-shaped lesion with base at cortex in a vascular distribution (in 70%) due to vasogenic + cytotoxic edema

  • mass effect (23 75%): sulcal effacement, transtentorial herniation, displaced subarachnoid cisterns + ventricles

  • bland infarct may be transformed into hemorrhagic infarct after 2 4 days (due to leakage of blood from ischemically damaged capillary endothelium following lysis of intraluminal clot + arterial reperfusion)

• CECT:

  • decreased meningeal + intravascular contrast enhancement

  • increased parenchymal enhancement

• MR:

  • intravascular enhancement sign (77%)

    • = Gd-pentetate enhancement of cortical arterial vessels in area of brain injury after 1 3 days (due to slow arterial blood flow provided by collateral circulation via leptomeningeal anastomoses)

  P.301

  
  

  • meningeal enhancement sign (33%) = Gd-pentetate enhancement of meninges adjacent to infarct after 2 6 days (due to meningeal inflammation)

• Angio:

  • narrowed / occluded vessels supplying the area of infarction

  • delayed filling + emptying of involved vessels

  • early draining vein

  • luxury perfusion of infarcted area (rare) = loss of small vessel autoregulation due to local increase in pH

Subacute Ischemic Infarction

• Time period:

  7 30 days = paradoxical phase with resolution of edema + onset of coagulation necrosis

• NCCT:

  • fogging phenomenon = low-density area less apparent

  • decrease of mass effect + ex vacuo dilatation of ventricles (in 57%)

  • transient calcification (especially in children)

• CECT:

  • gyral blush + ring enhancement (breakdown of blood-brain barrier + luxury perfusion) for 2 8 weeks (in 65 80% within first 4 weeks)

  • no enhancement in 1/5 of patients

• MR:

  • Histo:

    vasogenic edema (= increased extracellular water) due to disruption of blood-brain barrier

  • hypointense on T1WI, hyperintense on T2WI

  • intravascular + meningeal enhancement signs resolve toward end of 1st week

  • gyriform parenchymal Gd-pentetate enhancement

    • Gyriform parenchymal enhancement permits differentiation of subacute from chronic infarction!

  • infarction flip-flops from hyperintense lesion to iso / hypointense lesion on ADC maps 5 10 days after ictus

Chronic Ischemic Infarction

• Time period:	months to years (>30 days)
  Histo:	demyelination + gliosis complete (focal brain atrophy after 8 weeks)

• cerebral atrophy + encephalomalacia + gliosis (HALLMARKS)

• possible calcification (especially in children)

• NCCT:

  • cystic foci of CSF density (= encephalomalacia) in vascular distribution

• MR:

  • patchy region with increased intensity on T2WI

  • gliosis (hyperintense on T2WI) often surrounding encephalomalacic region

  • wallerian degeneration (= antegrade degeneration of axons secondary to neuronal injury) of corticospinal tracts in the wake of old large infarcts that involve the motor cortex

Hemorrhagic Infarction

• Etiology:	lysis of embolus / opening of collaterals / restoration of normal blood pressure following hypotension / hypertension / anticoagulation causes extravasation in reperfused ischemic brain
  Incidence:	6% of clinically diagnosed brain infarcts, 20% of autopsied brain infarcts
  Path:	petechial hemorrhages in various degrees of coalescence
  Location:	corticomedullary junction

• CT:

  • hyperdensity (56 76 HU) appearing within a previously imaged hypodense acute ischemic infarct = hemorrhagic transformation (in 50 72%)

    • False negative:

      hematoma isoattenuating if hematocrit <20%

• MR:

  • hypointense area on T2WI within edema marking gyri = deoxyhemoglobin of acute hemorrhage

  • hyperintense area on T1WI = methemoglobin of subacute hematoma

Basal Ganglia Infarct

• = occlusion of small penetrating arteries at base of brain (lenticulostriate / thalamoperforating arteries) = lacunar infarct (infarcts <1 cm in size)

• Cause:

  • Embolism

  • Hypoperfusion

  • Carbon monoxide poisoning

  • Drowning

  • Vasculopathy (hypertension, microvasculopathy, aging)

• dense homogeneous enhancement outlining caudate nucleus, putamen, globus pallidus, thalamus

• dense round nodular enhancement / peripheral ring enhancement

Laminar Necrosis

• = ischemic changes affecting deep layers of the cortex (layers 3, 5, 6 are very sensitive to oxygen deprivation)

• MR:

  • acute stage

    • linear cortical hyperintensity on T1WI

    • contrast enhancement

    • white matter edema on T2WI

  • chronic stage

    • thin hypointense cortex

    • hyperintense white matter

    • enlargement of CSF spaces

Lacunar Infarction

• [lacuna, Latin = hole]

• = small deep infarcts in the distal distribution of penetrating vessels (lenticulostriate, thalamoperforating, pontine perforating arteries, recurrent artery of Heubner)

• Cause:	occlusion of small penetrating end arteries at base of brain due to fibrinoid degeneration
  Age:	usually >55 years; M:F = 1:1
  Predisposed:	hypertension / diabetes
  Incidence:	15 20% of all strokes
  Path:	lacune = small hole of encephalomalacia traversed by cobweblike fibrous strands; if multiple = tat lacunaire (lacunar state)
  Histo:	microatheroma = hyalinization + arteriolar sclerosis resulting in thickening of vessel wall + luminal narrowing

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• pure motor / pure sensory stroke

• ataxic hemiparesis

• vascular dementia

• Location:

  upper two-thirds of putamen > caudate > thalamus > pons > internal capsule

• small discrete foci of hypodensity between 3 mm and 15 mm in size (most <1 cm in diameter)

• may enhance in late acute / early subacute stage

• unilateral pontine infarcts are sharply marginated at midline

• higher in signal intensity than CSF (due to marginal gliosis)

• DDx:

  enlarged Virchow-Robin spaces, neurocysticercosis

TIA and RIND

• hypodense small lesions located peripherally near / within cortex without enhancement

• lesions detected in only 14%, contralateral lesion present in 14% (CT of marginal value)

Infection in immunocompromised patients

• Cause:	underlying malignancy, collagen disease, cancer therapy, AIDS, immunosuppressive therapy in organ transplants
  Organism:	Toxoplasma, Nocardia, Aspergillus, Candida, Cryptococcus

• poorly defined hypodense zones with rapid enlargement in size + number, particularly affecting basal ganglia + centrum semiovale (poorly localized + encapsulated infection with poor prognosis)

• ring / nodular enhancement (sufficient immune defenses): Toxoplasma, Nocardia

• enhancement may be blunted by steroid Rx

• AIDS may be associated with:

  • thrombocytopenia, lymphoma, plasmacytoma, Kaposi sarcoma, progressive multifocal leukoencephalopathy

Iniencephaly

• = complex developmental anomaly characterized by

  • exaggerated lordosis

  • rachischisis

  • imperfect formation of skull base at foramen magnum

• M:F = 1:4

• Associated with other anomalies in 84%:

  • anencephaly, encephalocele, hydrocephalus, cyclopia, absence of mandible, cleft lip / palate, diaphragmatic hernia, omphalocele, gastroschisis, single umbilical artery, CHD, polycystic kidney disease, arthrogryposis, clubfoot

• dorsal flexion of head

• abnormally short + deformed spine

• Prognosis:	almost uniformly fatal
  DDx:	(1) Anencephaly
  	(2) Klippel-Feil syndrome
  	(3) Cervical myelomeningocele

Intracranial Hypotension

• = rare cause of orthostatic headache worsening in the upright position

• Cause:

  • persistent CSF leak:

    • diagnostic lumbar puncture, spinal anesthesia, myelography, craniotomy, spinal surgery, trauma

  • spontaneously:

    • rupture of Tarlov cyst, dehydration, hyperpnea, uremia, diabetic coma

  • low CSF opening pressure of <80 mm H₂O

  • sagging of posterior fossa:

    • low-lying cerebellar tonsils

    • elongation of 4th ventricle

    • effacement of prepontine cistern

  • diffuse smooth linear pachymeningeal enhancement (due to increased intracranial venous blood flow compensating for the CSF loss)

  • bilateral subdural effusions

  • enlarged pituitary gland

  • Rx:

    conservative therapy with bed rest; autologous epidural blood patch

Intraventricular Neurocytoma

• = INTRAVENTRICULAR NEUROBLASTOMA

• = benign primary neoplasm of lateral + 3rd ventricles

• Incidence:	unknown; tumor frequently mistaken for intraventricular oligodendroglioma
  Age:	20 40 years
  Histo:	uniform round cells with central round nucleus + fine chromatin stippling perivascular pseudorosettes, focal microcalcifications (closely resembling oligodendroglioma but with neuronal differentiation into synapselike junctions)
  Location:	body frontal horn of lateral ventricle, may extend into 3rd ventricle

• entirely intraventricular well-circumscribed tumor, coarsely calcified (69%), containing cystic spaces (85%)

• mild to moderate contrast enhancement

• attachment to septum pellucidum CHARACTERISTIC

• hemorrhage into tumor / ventricle

• hydrocephalus

• peritumoral edema extremely uncommon

• MR:

  • isointense relative to cortical gray matter on T1WI + T2WI with heterogeneous areas due to calcifications, cystic spaces, vascular flow voids (62%)

  • Rx:

    complete surgical resection

  • DDx:

    • Intraventricular oligodendroglioma (no hemorrhage)

    • Astrocytoma (peritumoral edema in 20%)

    • Meningioma (almost exclusively in trigone, >30 years of age)

    • Ependymoma (in + around 4th ventricle / trigone, in childhood)

    • Subependymoma (in + around 4th ventricle, young adults)

    • Choroid plexus papilloma (body + posterior horn of lateral ventricle, intense enhancement, younger patient)

    • Colloid cyst (anterior 3rd ventricle / foramen of Monro, calcifications uncommon)

    • Craniopharyngioma (extraventricular origin)

    • Teratoma + dermoid cyst (fat attenuation)

Jakob-Creutzfeldt Disease

• = rare transmissible disease developing over weeks

• Cause:

  prion = protein devoid of functional nucleic acid; ? slow-virus infection

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• Age:	older adults
  Histo:	classified as spongiform encephalopathy

• rapidly progressive dementia, ataxia, myoclonus

• hyperintense lesions in head of caudate nucleus + putamen, bilaterally on T2WI

• NO gadolinium enhancement of lesions

• NO white matter involvement

• Prognosis:

  usually fatal within 1 year of onset

Joubert Syndrome

• = autosomal recessive disorder characterized by clinical presentation of

  • hypotonia

  • ataxia

  • global developmental delay

• episodic hyperpnea

• abnormal eye movement

• mental retardation

• Path:	(1) nearly total aplasia of cerebellar vermis
  	(2) dysplasia + heterotopia of cerebellar nuclei
  	(3) near total absence of pyramidal decussation
  	(4) anomalies in structure of inferior olivary nuclei, descending trigeminal tract, solitary fascicle, dorsal column nuclei

• 4th ventricle triangle-shaped at mid-level + bat-wing shaped superiorly

• cerebellar hemispheres appose one another in midline

• superior cerebellar peduncles surrounded by CSF

• small isthmus + midbrain in AP diameter (due to absence of decussation of superior cerebellar peduncles)

• molar tooth sign = small brainstem + elongated thickened superior cerebellar peduncles (virtually PATHOGNOMONIC)

• supratentorial anomalies distinctly uncommon (except for cortical dysplasia + gray matter heterotopia)

• DDx:

  Dandy-Walker malformation

Lipoma

• = congenital tumor developing within subarachnoid space as a result of abnormal differentiation of the meninx primitiva (which differentiates into pia mater, arachnoid, inner meningeal layer of dura mater)

• Incidence:	<1% of brain tumors
  Age:	presentation in childhood / adulthood

• Associated with congenital anomalies:

  • in anterior location: various degrees of agenesis of corpus callosum (in 50 80%)

  • in posterior location (in <33%)

• asymptomatic in 50%

• Location:

  • (usually in subarachnoid space) callosal cistern (25 50%), sylvian fissure, quadrigeminal cistern, chiasmatic cistern, interpeduncular cistern, CP angle cistern, cerebellomedullary cistern, tuber cinereum, choroid plexus of lateral ventricle

• CT:

  • well-circumscribed mass with CT density of 100 HU

  • occasionally calcified rim (esp. in corpus callosum)

  • no enhancement

• MR:

  • hyperintense mass on T1WI + less hyperintense on T2WI (CHARACTERISTIC)

Lipoma of Corpus Callosum

• = congenital pericallosal tumor not actually involving the corpus callosum as a result of faulty disjunction of neuroectoderm from cutaneous ectoderm during process of neurulation

• Incidence:

  approx. 30% of intracranial lipomas

• Associated with:

  • anomalies of corpus callosum (30% with small posterior lipoma, 90% with large anterior lipoma)

  • frontal bone defect (frequent) = encephalocele

  • cutaneous frontal lipoma

• in 50% symptomatic:

• seizure disorders, mental retardation, dementia

• emotional lability, headaches

• hemiplegia

• Plain film:

  • midline calcification with associated lucency of fat density

• CT:

  • area of marked hypodensity immediately superior to lateral ventricles with possible extension inferiorly between ventricles / anteriorly into interhemispheric fissure

  • curvilinear peripheral / nodular central calcification within fibrous capsule (more common in anterior compared with posterior lipomas)

• MR:

  • hyperintense midline mass superior + posterior to corpus callosum on T1WI

  • no callosal fibers dorsal to lipoma

  • branches of pericallosal artery frequently course through lipoma

• DDx:

  dermoid (denser, extraaxial), teratoma

Lissencephaly

• = AGYRIA-PACHYGYRIA COMPLEX

• = smooth brain = most severe of neuronal migration anomalies; autosomal recessive disease with abnormal cortical stratification

• agyria = absence of gyri on brain surface

• pachygyria = focal / diffuse area of few broad flat gyri

• A. COMPLETE LISSENCEPHALY = AGYRIA

  • most frequently parieto-occipital in location

• B. INCOMPLETE LISSENCEPHALY

  • = areas of both agyria + pachygyria, pachygyric areas most frequently in frontal + temporal regions

• Histo:

  thick gray + thin white matter with only four cortical layers I, III, V, VI (instead of six layers)

• Often associated with:

  • CNS anomalies: microcephaly, hydrocephalus, agenesis of corpus callosum, hypoplastic thalami

  • micromelia, clubfoot, polydactyly, camptodactyly, syndactyly, duodenal atresia, micrognathia, omphalocele, hepatosplenomegaly, cardiac + renal anomalies

• micrencephaly

• severe mental retardation

• hypotonia + occasional myoclonic spasm

• early seizures refractory to medication

• smooth thickened cortex with diminished white matter

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• figure-eight appearance of cerebrum on axial images due to shallow widened vertically oriented sylvian fissures

• absent / shallow sulci and gyri (brain looks similar to that in fetuses <23 weeks GA)

• middle cerebral arteries close to inner table of calvarium (absence of sulci)

• small splenium + absent rostrum of corpus callosum

• hypoplastic brainstem (lack of formation of corticospinal + corticobulbar tracts)

• ventriculomegaly (atrium + occipital horns)

• midline round calcification in area of septum pellucidum (CHARACTERISTIC)

• polyhydramnios (50%)

• Prognosis:	death by age 2
  DDx:	polymicrogyria (= formation of multiple small gyri mimicking pachygyria on CT + MR, most common around sylvian fissures, broad thickened gyri with frequent gliosis subjacent to polymicrogyric cortex as the most important differentiating feature)

Lymphoid Hypophysitis

• = rare inflammatory autoimmune disorder with lymphocytic infiltration of pituitary gland

• Associated with:

  thyrotoxicosis + hypopituitarism

• Age:

  almost exclusively in early postpartum women

• headaches, vision loss, inability to lactate / to resume normal menses

• enlarged homogeneously enhancing pituitary gland

• Prognosis:	spontaneous regression
  Rx:	steroids (reduction in pituitary size on follow-up)

Lymphoma

• A. PRIMARY CNS LYMPHOMA (PCNSL) in 93%

  • = RETICULUM CELL SARCOMA = HISTIOCYTIC LYMPHOMA = microglioma

  • = high-grade B-cell NHL with strong association with Epstein-Barr virus infection

  • Risk:

    increased (350-fold) in immunocompromised patients: AIDS (2 10%), renal transplant, Wiskott-Aldrich syndrome, immunoglobulin deficiency A, rheumatoid arthritis, progressive multifocal leukoencephalopathy

  • Associated with:

    intraocular lymphoma

  • B. SECONDARY (7%) = SYSTEMIC LYMPHOMA

    • Type:	NHL > Hodgkin disease
      Location:	tendency for dura mater + leptomeninges

    • palsies of cranial nerves III, VI, VII

    • hydrocephalus

  • Primary lymphoma is indistinguishable from secondary!

  • Clues:	(1) multicentric involvement of deep hemispheres
    	(2) association with immunosuppression
    	(3) rapid regression with corticosteroids / radiation therapy = ghost tumor

  • Prevalence:	0.3 2% of all intracranial tumors; 7 15% of all primary brain tumors (equivalent to meningioma + low-grade astrocytoma); M > F
    Peak age:	30 50 years; M:F = 2:1
    Histo:	atypical pleomorphic B-cells mixed with reactive T-cells infiltrate blood vessel walls + cluster within perivascular (Virchow-Robin) spaces simulating vasculitis

  • symptoms of rapidly enlarging mass (60%)

  • symptoms of encephalitis (<25%)

  • stroke (7%)

  • cranial nerve palsy, demyelinating disease

  • personality changes, headaches, seizures

  • cerebellar signs, motor dysfunction

  • CSF cytology positive in 4 25 43%: elevated protein, mononuclear / blast / other lymphoma cells

  • Location:	supratentorial:posterior fossa = 3 9:1; paramedian structures preferentially affected; white matter + corpus callosum (55%), deep central gray matter of basal ganglia + thalamus + hypothalamus (17%), posterior fossa + cerebellum (11%), spinal cord (1%); multicentricity in 11 47%
    Site:	abut ventricular ependyma + meninges (12 30%); butterfly pattern of frontal lobe lymphoma; dural involvement may mimic meningioma (rare)
    Spread:	typically infiltrating; may cross anatomic boundaries + midline (crosses corpus callosum), diffuse leptomeningeal spread; subependymal spread with ventricular encasement (= rim-lymphoma)

  • commonly large discrete solitary lesion (57%)

    • Large lesion suggests lymphoma!

  • small + symmetric multiple nodular lesions (43 81%)

  • diffusely infiltrating lesion with blurred margins

  • spontaneous regression (unique feature)

  • Steroids may inhibit contrast enhancement

  • CT:

    • usually mildly hyperdense (33%) because of high nuclear-to-cytoplasmic ratio

    • occasionally isodense / low-density area (least common)

    • little mass effect with paucity of peritumoral edema

    • homogeneously dense + well-defined / irregular + patchy periventricular contrast enhancement

    • commonly thick-walled ring enhancement in immunocompetent patient

  • MR (superior to CT):

    • well-demarcated round / oval / gyral-shaped (rare) mass

    • relatively little mass effect for size

    • isointense / slightly hypointense (due to high cell density) relative to gray matter on T1WI

    • hypo- to isointense / hyperintense (less common) relative to gray matter on T2 / FLAIR:

      • ring pattern (= central necrosis with densely cellular rim in hyperintense sea of edema ) typical in immunocompromised patients

      • intense ring-shaped contrast enhancement on T1WI

    • irregular sinuous / gyral-like contrast enhancement or homogeneous enhancement:

      • solid homogeneous enhancement in immunocompetent patient

      • irregular heterogeneous ringlike mass in immunocompromised patient

      • periventricular enhancement is highly SPECIFIC (DDx: CMV ependymitis)

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  • Angio:

    • avascular mass / tumor neovascularity

    • focal blush in late arterial-to-capillary phase persisting well into venous phase

    • arterial encasement

    • dilated deep medullary veins

  • NUC:

    • increased uptake of thallium-201 on SPECT (100% sensitive, 93% specific)

    • increased uptake of C-11 methionine on PET

  • Prognosis:	median survival of 45 days for AIDS patients; median survival of 3.3 months for immuno-competent patients; improved with radiation therapy (4.5 20 months) + chemotherapy
    Rx:	sensitive to radiation therapy

  • DDx:

    • Neoplastic disorders

      • Glioma (may be bilateral with involvement of basal ganglia + corpus callosum, may show dense homogeneous enhancement with vascularity)

      • Metastases (known primary, at gray-white matter junction)

      • Primitive neuroectodermal tumor

      • Meningioma

    • Infectious disease (multicentricity)

      • Abscess, especially toxoplasmosis (large edema)

      • Sarcoidosis

      • Tuberculosis

    • Demyelinating disease

      • Multiple sclerosis

      • Progressive multifocal leukoencephalopathy

Spinal Epidural Lymphoma

• invasion of epidural space through intervertebral foramen from paravertebral lymph nodes

• destruction of bone with vertebral collapse (less common)

• direct involvement of CNS (rare)

Leukemia

• CNS affected in 10% of patients with acute leukemia

• enlargement of ventricles + sulci due to atrophy (31%)

• sulcal / fissural / cisternal enhancement (meningeal infiltration) in 5%

• Prognosis:

  3 5 months survival if untreated

Medulloblastoma

• Most malignant infratentorial neoplasm; most common neoplasm of posterior fossa in childhood (followed by cerebellar pilocytic astrocytoma)

• Incidence:	15 20% of all pediatric intracranial tumors; 30 40% of all posterior fossa neoplasms in children; 2 10% of all intracranial gliomas
  Origin:	from external granular layer of inferior medullary velum (= roof of 4th ventricle)
  Histo:	completely undifferentiated cells (50%), desmoplastic variety (25%), glial / neuronal differentiation (25%)
  Age:	40% within first 5 years of life; 75% in first decade; between ages 5 and 14 (2/3); between ages 15 and 35 (1/3); M:F = 2 4:1

• duration of symptoms <1 month prior to diagnosis: nausea, vomiting, headache, increasing head size, ataxia

• Site:	(a) vermis cerebelli + roof of 4th ventricle (younger age group) in 91%
  	(b) cerebellar hemisphere (older age group)
  Size:	usually >2 cm in diameter

• well-defined vermian mass with widening of space between cerebellar tonsils

• encroachment on 4th ventricle / aqueduct with hydrocephalus (85 95%)

• shift / invagination of 4th ventricle

• rapid growth with extension into cerebellar hemisphere / brainstem (more often in adults)

• extension into cisterna magna + upper cervical cord, occasionally through foramina of Luschka into cerebellopontine angle cistern

• mild / moderate surrounding edema (90%)

• CT:

  • Classic features in 53%:

    • slightly hyperdense (70%) / isodense (20%) / mixed (10%) lesion

    • rapid intense homogeneous enhancement (97%) due to usually solid tumor

  • Atypical features:

    • cystic / necrotic areas (10 16%) with lack of enhancement

    • calcifications in 13%

    • hemorrhage in 3%

    • supratentorial extension

• MR:

  • mixed / hypointense on T1WI

  • hypo- / iso- / hyperintense on T2WI

  • usually homogeneous Gd-DTPA enhancement with hypointense rim

  • cerebellar folia blurred

• Cx:	(1) Subarachnoid metastatic spread (30 100%) via CSF pathway to spinal cord + cauda equina ( drop metastases in 40%), cerebral convexities, sylvian fissure, suprasellar cistern, retrograde into lateral + 3rd ventricle
  	continuous frosting of tumor on pia
  	(2) Metastases outside CNS (axial skeleton, lymph nodes, lung) after surgery

• Rx:

  surgery + radiation therapy (extremely radiosensitive)

• DDx of midline medulloblastoma:

  • ependymoma, astrocytoma (hypodense)

• DDx of eccentric medulloblastoma:

  • astrocytoma, meningioma, acoustic neuroma

Meningeal Carcinomatosis

• Source:

  • Primary CNS tumor: medulloblastoma, glioblastoma, pineal tumors

  • Secondary tumor: breast, lung, melanoma

• Histo:	adenocarcinoma (75%)
  Spread:	hematogenous, lymphatic, perineural, shedding from parenchymal metastases

• simultaneous occurrence of symptoms localized to more than one area!

• headaches (50%)

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• cranial nerve deficits (40%): visual disturbances, diplopia, hearing loss, facial numbness

• mental status changes: lethargy + confusion (20%)

• seizures (15%)

• progressive asymmetric weakness of extremities

• cauda equina syndrome

• Dx:	lumbar puncture positive in 45 55% (1st puncture), 80% (after several taps)
  Location:	basal cisterns, lumbar spine (areas of CSF stasis)

• communicating hydrocephalus (tumor interferes with CSF reabsorption in pacchionian granulations near vertex)

• ischemic changes secondary to vasculitis (rare)

• Patterns:

  • Dural Meningeal Carcinomatosis

    • rarely associated with positive cytology

    • short discontinuous thin sections of enhancement localized / diffuse curvilinear underneath inner table in expected position of dura

  • Leptomeningeal Carcinomatosis

    • frequently associated with positive cytology

    • thin rim of subarachnoid enhancement following convolutions of gyri coating the surface of brain

    • discrete leptomeningeal nodules

    • invasion of underlying brain with mass effect + edema

  • DDx:

    • bacterial / fungal meningitis, postoperative changes (fibrosis), previous subarachnoid hemorrhage, idiopathic cranial pachymeningitis, vasculitis, extramedullary hematopoiesis, primary leptomeningeal gliomatosis, amyloidosis, glioneural heterotopia, Castleman disease, Gaucher disease

Meningioma

• Incidence:	most common extraaxial tumor; 15 18% of intracranial tumors in adults; 1 2% of primary brain tumors in children; 33% of all incidental intracranial neoplasms
  Origin:	derived from meningothelial cells concentrated in arachnoid villi (= arachnoid cap cells ), which penetrate the dura (villi are numerous in large dural sinuses, in smaller veins, along root sleeves of exiting cranial + spinal nerves, choroid plexus)

• Histologic classification:

  • benign behavior pattern

    • (a) fibroblastic type = fibrous type

      interwoven bands of spindle cells + collagen + reticulin fibers

  • (b) transitional type = mixed type

    features of meningothelial + fibroblastic forms

• aggressive imaging appearance

  • (c) meningothelial = syncytial typeforming a syncytium of closely packed cells with indistinct borders

  • (d) angioblastic / malignant type

    probably hemangiopericytoma / hemangioblastoma arising from vascular pericytes

• Age:	peak incidence 45 years (range 35 70 years); rare <20 years (in children >50% malignant, M > F);M:F = 1:2 to 1:4
  Associated with:	neurofibromatosis type 2 (multiple meningiomas, occurrence in childhood), basal cell nevus syndrome

  • 10% of patients with multiple meningiomas have type 2 neurofibromatosis!

  • Most common radiation-induced CNS tumor with latency period of 19 35 years varying with dosage!

• Types:

  • Globular meningioma (most common):

    • compact rounded mass with invagination of brain; flat at base; contact to falx / tentorium / basal dura / convexity dura

  • Meningioma en plaque:

    • pronounced hyperostosis of adjacent bone particularly along base of skull; difficult to distinguish hyperostosis from tumor cloaking the inner table (DDx: Paget disease, chronic osteomyelitis, fibrous dysplasia, metastasis)

  • Multicentric meningioma (2 9%):

    • 16% in autopsy series; tendency to localize to a single hemicranium; present clinically at earlier age; global / mixed; CSF seeding is exceptional; in 50% associated with neurofibromatosis type 2

  • Location:

    • Supratentorial (90%)

      • convexity = lateral hemisphere (20 34%)

      • parasagittal = medial hemisphere (18 22%):

        • falcine meningioma (5%) below superior sagittal sinus, usually extending to both sides

      • sphenoid ridge + middle cranial fossa (17 25%)

      • frontobasal at olfactory groove (10%)

    • Infratentorial (9 15%)

      • cerebellar convexity (5%)

      • tentorium cerebelli (2 4%)

      • cerebellopontine angle (2 4%)

      • clivus (<1%)

    • Spine (12%)

  • Atypical location:

    • cerebellopontine angle (<5%)

    • optic nerve sheath (<2%)

    • intraventricular (2 5%): 80% in lateral (L > R), 15% in 3rd, 5% in 4th ventricle; from infolding of meningeal tissue during formation of choroid plexus

      • Most common trigonal intraventricular mass in adulthood!

    • ectopic = extradural (<1%): intradiploic space, outer table of skull, scalp, paranasal sinus, parotid gland, parapharyngeal space, mediastinum, lung, adrenal gland

  • Plain film:

    • hyperostosis at site close to / within bone (exostosis, enostosis, sclerosis)

    • Hyperostosis does NOT indicate tumor infiltration!

    • blistering at paranasal sinuses (ethmoid, sphenoid) sclerosis (= pneumosinus dilatans)

    • enlarged meningeal grooves (if location in vault), enlarged foramen spinosum

    • calcification (= psammoma bodies)

  • CT:

    • sharply demarcated well-circumscribed slowly growing mass

    • wide attachment to adjacent dura mater

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    • cortical buckling of underlying brain

    • hyperdense (70 75% due to psammomatous calcifications) / isodense lesion on NECT

    • calcifications in circular / radial pattern in 20 25% (DDx: osteoma)

    • intraosseous meningioma = permeation of bone with intra- and extracerebral soft-tissue component (DDx: fibrous dysplasia)

    • hyperostosis of adjacent bone (18%)

    • intense uniform enhancement on CECT (absence of blood-brain barrier)

    • minimal peritumoral edema (in up to 75%): NO correlation between tumor size + amount of edema (DDx: intraaxial lesion)

    • cystic component: major in 2%, minor in 15%

  • MR (100% detection rate with gadolinium DTPA):

    • hypo- to isointense on T1WI + iso- to hyperintense on T2WI (intensity depends on amount of cellularity versus collagen elements):

    • tends to follow cortical signal intensity

    • homogeneous / heterogeneous texture (tumor vascularity, cystic changes, calcifications)

    • arcuate bowing of white matter + cortical effacement

    • tumor-brain interface of low-intensity vessels + high-intensity cerebrospinal cleft on T2WI

    • contrast enhancement for 3 60 minutes on T1WI as high as 148% over brain parenchyma

    • dural tail sign (in 60 72% of meningiomas)

    • encasement + narrowing of vessels

  • Angio:

    • mother-in-law phenomenon (contrast material shows up early and stays late into venous phase)

    • sunburst / spoke-wheel pattern of tumor vascularity with hypervascular cloudlike stain

    • early draining vein (rare: perhaps in angioblastic meningioma)

    • en plaque meningioma is poorly vascularized

  • Vascular supply:

    • External carotid artery (almost always):

      • vault: middle meningeal artery

      • sphenoid plane + tuberculum: recurrent meningeal branch of ophthalmic a.

      • tentorium: meningeal branch of meningohypophyseal trunk of ICA

      • clivus + posterior fossa: vertebral artery / ascending pharyngeal artery

      • falx: partly middle meningeal artery + others

    • Internal carotid artery (rare):

      • intraventricular: choroidal vessels

    • Cx:

      local invasion of venous sinuses

Atypical Meningioma (15%)

• Low attenuation area of necrosis, old hemorrhage, cyst formation, fat (DDx: malignant glioma, metastasis)

  • Cystic meningioma (2 4%)

    Frequency:	55 65% in 1st year of life; 10% in children
    Type I =	intratumoral central / eccentric cyst (ischemic necrosis, microcystic degeneration, breakdown of hemorrhagic products); often associated with meningothelial / microcystic / atypical / malignant histologic subtypes
    Type II =	extratumoral intraparenchymal cyst (arachnoid cyst / reactive gliosis / liquefactive necrosis of adjacent brain)
    Type III =	trapped CSF (DDx: cystic / necrotic glioma)

  • Lipoblastic / xanthomatous meningioma (5%)metaplastic change of meningothelial cells into adipocytes

• Heterogeneous / ring enhancement (secondary to bland tumor infarction / necrosis in aggressive histologic variants / true cyst formation from benign fluid accumulation)

• En plaque morphology

• Comma shape = combination of semilunar component bounded by dural interface + spherical component growing beyond dural margin

• Sarcomatous transformation with spread over hemisphere + invasion of cerebral parenchyma (leptomeningeal supply)

• Meningeal hemangiopericytoma

  • multilobulated contour

  • narrow dural base / mushroom shape

  • large intratumoral vascular signals

  • bone erosion

  • prominent peritumoral edema

  • multiple irregular feeding vessels on angiogram

Sphenoid Wing Meningioma

• Hyperostotic meningioma en plaque

  • slowly progressive unilateral painless exophthalmos

  • numbness in distribution of cranial nerve V₁ + V₂

  • headaches, seizures

• Meningioma arising from middle third of sphenoid ridge

  • headaches, seizures

  • compression of regional frontal + temporal lobes

• Meningioma arising from clinoid process

  • encasement of carotid + middle cerebral arteries

  • compression of optic nerve + chiasm

• Meningioma of planum sphenoidale

  • subfrontal growth + posterior growth into sella turcica and clivus

  • hyperostotic blistering of planum sphenoidale

Suprasellar Meningioma

• Incidence:	10% of all intracranial meningiomas
  Origin:	from arachnoid + dura along tuberculum sellae / clinoids / diaphragma sellae / cavernous sinus with secondary extension into sella; NOT from within pituitary fossa

• hypothalamic / pituitary dysfunction (rare)

• irregular hyperostosis = blistering adjacent to sinus (HALLMARK of meningiomas at planum sphenoidale / tuberculum sellae)

• pneumatosis sphenoidale = increased pneumatization of sphenoid in area of anterior clinoids + dorsum sellae (DDx: normal variant)

• broad base of attachment

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• intense homogeneous enhancement (may be impossible to differentiate from supraclinoid carotid aneurysm on CT)

• blood supply: posterior ethmoidal branches of ophthalmic artery, branches of meningohypophyseal trunk

• MR:

  • large mass isointense to gray matter on T1WI + T2WI

  • hyperintense flattened pituitary gland within floor of sella

  • marked homogeneous enhancement on T1WI

• DDx:

  metastasis, glioma, lymphoma

Meningitis

• = infection of the pia mater + arachnoid + adjacent CSF

• 1. Pachymeningitis: infection of dura mater

• 2. Leptomeningitis: infection of pia matter / arachnoid (most common) + CSF

• headaches, stiff neck

• confusion, disorientation

• positive CSF lab analysis

• ROLE of CT and MR:

  • to exclude parenchymal abscess, ventriculitis, localized empyema

  • to evaluate paranasal sinuses / temporal bone as source of infection

  • to monitor complications: hydrocephalus, subdural effusion, infarction

Purulent / Bacterial Meningitis

• Cause:

  otitis media / sinusitis

• Organism:

  • (a) adults:	Meningococcus, Diplococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus
    (b) children:	Escherichia coli, Citrobacter, -hemolytic Streptococcus

  • fever, headache, seizures

  • altered consciousness, neck stiffness

  • NECT:

    • often normal

    • increased density in subarachnoid space (increased vascularity), esp. in children

    • small ventricles secondary to diffuse cerebral edema

  • CECT:

    • marked curvilinear meningeal enhancement over cerebrum (frontal + parietal lobes) and interhemispheric + sylvian fissures

    • obliteration of basal cisterns with enhancement (common)

  • MR (most sensitive modality):

    • no abnormality on nonenhanced MR in most cases

    • hyperintense obliterated basal cisterns on proton-density images + intermediate intensity on T1WI

    • hyperintense plaques on T2WI

    • leptomeningeal enhancement with Gd-DTPA (in chronic infection)

  • Cx:

    • Cerebritis

    • Ventriculitis = ependymitis (secondary to retrograde spread)

    • Brain atrophy

    • Brain infarction (arteritis, venous thrombosis)

    • Subdural effusion [sterile subdural effusion secondary to H. influenzae meningitis (in children) may turn into subdural empyema]

    • Hydrocephalus (cellular debris blocking foramen of Monro, aqueduct, 4th ventricular outlet / intraventricular septa / arachnoid adhesions)

    • Cranial nerve dysfunction

  • Prognosis:

    • Cerebral infarction + edema are predictive of poor outcome

    • Enlargement of ventricles + subarachnoid spaces + subdural effusions have no predictive value

  • Mortality:	10% for H. influenzae + meningococcus,
    	30% for Pneumococcus (5th common cause of death in children between 1 and 4 years of age)

  • DDx:

    meningeal carcinomatosis

Granulomatous Meningitis

• Histo:

  thick exudate, perivascular inflammation, granulation tissue + reactive fibrosis

  • (1) Tuberculous meningitis = basilar meningitis:

    • part of generalized miliary tuberculosis / primary tuberculous infection

  • (2) Sarcoidosis (in 5% of sarcoidosis cases)

    • Histo:

      granulomatous infiltration of leptomeninges

    • nodular pattern (DDx from bacterial causes)

    • thick meningeal plaques over convexities (mimicking meningioma)

    • marked enhancement

    • may be associated with single / multiple intracerebral masses

    • Cx:

      cranial nerve palsy, hypothalamic-pituitary dysfunction, chronic meningitis

  • (3) Fungal meningitis: cryptococcosis, candidiasis, coccidioidomycosis (endemic), blastomycosis, mucormycosis (diabetics), nocardiosis, actinomycosis, aspergillosis (under chronic corticosteroid therapy)

  • acute life-threatening process / chronic indolent disease

  • May be associated with:

    cerebritis, abscess formation

  • hydrocephalus

  • CT:

    • obliteration of basal cisterns, sylvian fissure, suprasellar cistern (isodense cisterns secondary to filling with debris)

    • intense contrast enhancement of gyri + involved subarachnoid spaces

    • calcification of meninges

    • decreased attenuation of white matter

  • MR:

    • high-signal intensity of basilar cisterns on T2WI

    • enhancement with gadopentetate dimeglumine

  • Cx:	(1)	Hydrocephalus (obliteration of basal cisterns; blocking of CSF flow + CSF absorption)
    	(2) Infarction (due to arteritis)

Mesial Temporal Sclerosis

• Cause:	long-standing temporal lobe epilepsy
  Histo:	marked neuronal loss throughout hippocampal subfields with relative sparing of the CA2 subfield

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• Mechanism for excitotoxicity-induced neuronal death:

  • seizures cause excessive neuronal depolarization, which causes overproduction of excitory amino acid neurotransmitters, which cause excessive activation of N-methyl-D-aspartate receptors, which cause unregulated entry of Ca²⁺, which causes neuronal swelling with cytotoxic edema

• increased signal intensity + decreased volume of hippocampus compared to contralateral side on T2WI

• Associated limbic system findings:

  • ipsilateral atrophy of fornix (55%)

  • ipsilateral atrophy of mamillary body (26%)

• Associated extrahippocampal abnormalities:

  • increased signal intensity of anterior temporal lobe cortex (38%)

  • cerebral hemiatrophy (1%)

Metachromatic Leukodystrophy

• = MLD = most common hereditary (autosomal recessive) leukodystrophy (dysmyelinating disorder)

• Cause:

  deficiency of arylsulfatase A resulting in severe deficiency of myelin lipid sulfatide within macrophages + Schwann cells

• Age of presentation:

  before age 3 (2/3), in adolescence (1/3)

• A. LATE INFANTILE FORM

  • Age:

    2nd year of life

  • gait disorder + strabismus

  • impairment of speech

  • spasticity + tremor

  • intellectual deterioration

  • Prognosis:

    death within 4 years of onset

• B. JUVENILE FORM

  • Age:

    5 7 years

• C. ADULT FORM

  • organic mental syndrome

  • progressive corticospinal, corticobulbar, cerebellar, extrapyramidal signs

• progressive loss of hemispheric brain tissue

• CT:

  • symmetric low density of white matter adjacent to ventricles (esp. centrum ovale and frontal horns)

  • progressive atrophy

  • no contrast enhancement

• MR:

  • progressive symmetrical areas of hypointensity on T1WI

  • hyperintensity on T2WI (increased water)

• early sparing of internal capsule + subcortical U-fibers

• Prognosis:

  death within several years

Metastases to Brain

• Incidence:	14 37% of all intracranial tumors
  	Most common intracranial neoplasm!
  	Most common infratentorial mass in the adult

• Metastatic primary:

  • Six tumors account for 95% of all brain metastases:

    • Bronchial carcinoma (47%): RARELY squamous cell carcinoma

    • Breast carcinoma (17%)

    • GI-tract tumors (15%): colon, rectum

    • Hypernephroma (10%)

    • Melanoma (8%)

    • Choriocarcinoma

  • In childhood:

    • Leukemia / lymphoma

    • Neuroblastoma

  • Brain metastases from sarcomas are exceptionally rare!

• Location:

  • (a) corticomedullary junction of brain (most characteristic)

  • (b) subarachnoid space = carcinomatous meningitis (15%)

  • (c) subependymal spread (frequent in breast carcinoma)

  • (d) skull (5%)

  • N.B.:	CORTICAL METASTASES
    	minimal / no edema
    	may not be identified on T2WI
    	contrast-enhancement essential for detection

  • Presentation:

    • multiple lesions (2/3), single lesion (1/3)

    • cerebral hemispheres (57%), cerebellum (29%), brainstem (32%)

    • nodular deposits to dura are common

  • usually well-defined round masses:

    • multiple lesions of different sizes + locations

  • surrounding edema usually exceeds tumor volume

  • Contrast enhancement to disclose additional lesions!

  • CT:

    • hypodense on NECT (unless hemorrhagic / hypercellular)

    • solid enhancement in small tumors / ringlike enhancement in large tumors

  • MR (combination of T2WI + contrast-enhanced T1WI offer greatest sensitivity):

    • hypointense on T1WI

    • hypointense mass relative to edema / variable intensity on T2WI (due to hemorrhage, necrosis, cyst formation):

      • hypointensity more pronounced in melanoma + mucinous adenocarcinoma (paramagnetic effect)

    • homogeneous / ring / nodular mixed enhancement after Gd-DTPA; often more than one metastatic focus identified in region of colliding edema

    • asymmetric enhancement of dura with dural spread

    • leptomeningeal enhancement (eg, in metastatic ependymoma)

  • DDx:

    glioma (indistinct border, less well defined, lesser amount of vasogenic edema), multifocal inflammatory lesions

Hemorrhagic Metastases to Brain (in 3 4%)

• Malignant melanoma

• Choriocarcinoma

• Oat cell carcinoma of lung

• Renal cell carcinoma

• Thyroid carcinoma

• hyperdense without contrast

• hypervascular with contrast

• mnemonic:

  MR CT BB

  • Melanoma

  • Renal cell carcinoma

  • Choriocarcinoma

  • Thyroid carcinoma

  • Bronchogenic carcinoma

  • Breast carcinoma

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Cystic Metastasis to Brain

• Squamous cell carcinoma of lung

• Adenocarcinoma of lung

• DDx:

  benign cyst, abscess

Calcified Metastasis to Brain

• Mucin-producing neoplasm: GI, breast

• Cartilage- / bone-forming sarcoma

• Effective radio- and chemotherapy

Malignant Melanoma Metastatic to Brain

• Prevalence:

  39% at autopsy

• No clear consensus on contribution of paramagnetic effect of blood products versus melanin

• 1. Melanotic pattern (in 24 54%)

  • hyperintense on T1WI

  • iso- / hypointense on T2WI

  • Cause:

    free radicals in melanin + blood products

• Amelanotic pattern (38%)

  • hypo- / isointense on T1WI

  • hyper- / isointense on T2WI

• Other patterns

  • isointense on T1WI

  • hyperintense on T2WI

Microcephaly

• = clinical syndrome characterized by a head circumference below the normal range

• Incidence:

  1.6:1,000 or 1:6,200 1:8,500 births

• Etiology:

  • Undiagnosed intrauterine infection (toxoplasmosis, rubella, CMV, herpes, syphilis), toxic agents, drugs, hypoxia, irradiation, maternal phenylketonuria

  • Premature craniosynostosis

  • Chromosomal abnormalities (trisomies 13, 18, 21)

  • Meckel-Gruber syndrome

• Often associated with:

  • micrencephaly, macrogyria, pachygyria, atrophy of basal ganglia, decrease in dendritic arborization, holoprosencephaly

• AC:HC discrepancy

• head circumference <3 S.D. below the mean

• apelike sloping of forehead

• dilatation of lateral ventricles

• poor growth of fetal cranium

• intracranial contents may not be visible (rare)

• Prognosis:

  normal to severe mental retardation (depending on degree of microcephaly)

Mineralizing microangiopathy

• = RADIATION-INDUCED LEUKOENCEPHALOPATHY

• = sequelae of radiotherapy combined with methotrexate therapy for leukemia

• Incidence:	in 25 30% after >9 months after treatment
  Age:	childhood
  Cause:	deposition of calcium within small vessels of previously irradiated brain parenchyma

• 85% without neurologic deficits

• CT:

  • thin reticular / serrated linear / punctate calcifications near corticomedullary junction, especially in basal ganglia + frontal and posterior parietal lobes

  • symmetric low-attenuation process in white matter near corticomedullary area

• MR:

  • confluent diffuse periventricular distribution spreading peripherally with an irregular scalloped edge

Moyamoya Disease

• = progressive obstructive / occlusive cerebral arteritis affecting distal ICA at bifurcation into its branches (anterior 2/3 of circle of Willis), usually involving both hemispheres

• Etiology:	unknown
  Age:	predominantly in children + young adults
  Path:	endothelial hyperplasia + fibrosis without associated inflammatory reaction

• headaches

• behavioral disturbances

• recurrent hemiparetic attacks

• bilateral stenosis / occlusion of supraclinoid portion of internal carotid extending to proximal portions of middle + anterior cerebral arteries

• large network of vessels in basal ganglia ( puff of smoke ) + upper brainstem fed by basilar artery, anterior + middle cerebral arteries (dilatation of lenticulostriate + thalamoperforating arteries)

• anastomoses between dural meningeal + leptomeningeal arteries

• Cx:

  subarachnoid hemorrhage (occasionally)

Moyamoya Syndrome

• Etiology:

  neurocutaneous syndromes (neurofibromatosis), bacterial meningitis, periarteritis nodosa, head trauma, tuberculosis, oral contraceptives, atherosclerosis, sickle cell anemia

Multiple Sclerosis

• = most frequent form of chronic inflammatory demyelinating disease of unknown etiology, which reduces the lipid content and brain volume; characterized by a relapsing + remitting course

• Prevalence:	6:10,000 (higher frequency in cooler climates; increased incidence with positive family history)
  Cause:	? viral / autoimmune mechanism
  Peak age:	25 30 (range of 20 50) years; M:F = 2:3

• Histo:

  • acute stage: perivenular inflammation (at junctions of pial veins) with

    • hypercellularity (= infiltration of lipid-laden macrophages + lymphocytes)

    • well-demarcated demyelination (destruction of oligodendroglia with loss of myelin sheath)

    • reactive astrocytosis (= gliosis), initially with preservation of axons (= denuded axons) resulting in scar (= white matter plaque)

  • chronic stage: plaques advance to fibrillary gliosis with reduction in inflammatory component

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• Clinical forms:	(a) relapsing remitting
  	(b) relapsing progressive
  	(c) chronic progressive

• waxing and waning course with

  • numbness, dysesthesia, burning sensations

  • signs of brain neoplasm: headaches, seizures, dizziness, nausea, weakness, altered mental status

  • ataxia, diplopia

  • optic neuritis = retrobulbar pain, central loss of vision, afferent pupillary defect (Marcus Gunn pupil)

  • trigeminal neuralgia (1 2%)

• Schumacher criteria:

  • CNS dysfunction

  • involvement of two / more parts of CNS

  • predominant white matter involvement

  • two / more episodes lasting >24 hours less than 1 month apart

  • slow stepwise progression of signs + symptoms

  • at onset 10 50 years of age

• Rudick red flags (suggests diagnosis other than MS):

  • no eye findings

  • no clinical remission

  • totally local disease

  • no sensory findings

  • no bladder involvement

  • no CSF abnormality

• @ Brain

  • Number + extent of plaques correlate with duration of disease + degree of cognitive impairment

  • Location:

    • subependymal periventricular location (along lateral aspects of atria + occipital horns), corpus callosum, internal capsule, centrum semiovale, corona radiata, optic nerves, chiasm, optic tract, brainstem (ventrolateral aspect of pons at 5th nerve root entry), cerebellar peduncles (CLASSIC), cerebellum; rather symmetric involvement of cerebral hemispheres; subcortical U fibers NOT spared

    • 10% of MS lesions occur in gray matter!

  • lesion size of 1 25 (majority between 5 and 10) mm:

    • large lesions may masquerade as brain tumors

    • mass effect / edema in active lesions (infrequent)

  • ovoid lesions (86%) oriented with their long axis perpendicular to ventricular walls (due to perivenous demyelination; pathologically described as Dawson fingers )

  • chronic plaques do not enhance (due to intact blood-brain barrier)

  • diffuse cerebral atrophy (21 45 78%) in chronic MS: enlarged ventricles, prominent sulci

  • lesion enhancement (due to breakdown of blood-brain barrier in demyelinating process) irrespective of clinical symptoms:

    • peripheral enhancement of lesion

    • occasional central enhancement

• CT:

  • normal CT scan (18%)

  • periventricular (near atria) multifocal nonconfluent lesions with distinct margins (location not always correlating well with symptoms)

    • (a) NECT:	isodense / lucent
      	(b) CECT:	transient enhancement during acute stage (active demyelination) for about 2 weeks; may require double dose of contrast; ultimately disappearance / permanent scar

• MR (modality of choice; 95 99% specific):

  • well-marginated discrete foci of varying size with high-signal intensity on T2WI + proton density images (= loss of hydrophobic myelin produces increase in water content); hypointense on T1WI

  • abnormally bright signal of the optic nerve + variable swelling (optic neuritis) with loss of doughnut sign of the normal optic nerve complex

  • Gd-DTPA enhancement of lesions on T1WI (up to 8 weeks following acute demyelination with breakdown of blood-brain barrier)

    • characteristically as an incomplete ring

  • lesions on undersurface of corpus callosum (CHARACTERISTIC on sagittal images)

• @ Spinal cord (in up to 80%)

  • Most common demyelinating process of spinal cord!

  • In 12 33% without coexistent intracranial plaques!

  • number + extent of plaques correlate with degree of disability

• Location:	predilection for cervical cord
  Site:	eccentric involvement of dorsal + lateral elements abutting subarachnoid space

• atrophic plaques oriented along spinal cord axis

• length of plaque usually less than 2 vertebral body segments + width less than half of cross section

• acute tumefactive MS = cord swelling + enhancement

• cord atrophy in chronic MS

• DDx:	(1) Acute transverse myelitis
  	(2) Cord tumor (follow-up after 6 weeks without decrease in size of lesion)
  	(3) Trauma
  	(4) Infarct
  	(3) Postviral syndromes

• Rx:

  steroids (inciting rapid decrease in size of lesions + loss of enhancement)

• DDx:

  • Acute disseminated encephalomyelitis (ADEM), subacute sclerosing panencephalitis (lesions of similar age)

  • Lyme encephalopathy (skin rash)

  • Susac syndrome (encephalopathy + branch retinal artery occlusion + hearing loss)

  • Small vessel ischemia (patients >50 years of age, lesions <5 mm, not infratentorial)

  • AIDS, CNS vasculitis, migraine, radiation injury, lymphoma, sarcoidosis, tuberculosis, systemic lupus erythematosus, cysticercosis, metastases, multifocal glioma, neurofibromatosis, contusions

Myelinoclastic Diffuse Sclerosis

• = SCHILDER DISEASE

• = rare demyelinating disorder with episodic recurrence and remission

• Age:	children > adults; M:F = 1:1
  Histo:	selective confluent demyelination with relative axonal sparing, perivascular inflammatory infiltrate, reactive astrocytosis (indistinguishable from multiple sclerosis)

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• hemiplegia, aphasia, ataxia, blindness

• swallowing difficulties, progressive dementia

• increased intracranial pressure

• Location:

  centrum semiovale

• large bilateral white matter lesions with mass effect

• enhancement with IV contrast material

• Rx:	usually responsive to corticosteroids
  DDx:	(1) Acute disseminated encephalomyelitis (history of recent viral illness, monophasic course, lesions less confluent, no mass effect / enhancement)
  	(2) Adrenoleukodystrophy (bilaterally symmetric, confluent lesions, parietal location)
  	(3) Tumor, abscess, infarct

Neonatal Intracranial Hemorrhage

Germinal Matrix Bleed

• = GERMINAL MATRIX RELATED HEMORRHAGE

• Anatomy of germinal matrix:

  • = highly vascular gelatinous subependymal tissue adjacent to lateral ventricles in which the cells that compose the brain are generated; has its largest volume around 26 weeks GA; decreases in size with increasing fetal maturity; usually involutes by 32 34 weeks of gestation

  • Location:	greatest portion of germinal matrix above caudate nucleus in floor of lateral ventricle, tapering as it sweeps from frontal horn posteriorly into temporal horn, roof of 3rd + 4th ventricle
    Arterial supply:	via Heubner artery from ACA, striate branches of MCA, anterior choroidal a., perforating branches from meningeal aa.
    Capillary network:	persisting immature vascular rete = large irregular endothelial-lined channels devoid of connective tissue support (collagen and muscle)
    Venous drainage:	terminal vv., choroidal v., thalamostriate v. course anteriorly + feed into internal cerebral v. which has a posterior course

• Risk factors:

  • Prematurity

  • Low birth weight

  • Sex (M:F = 2:1)

  • Multiple gestations

  • Trauma at delivery

  • Prolonged labor

  • Hyperosmolarity

  • Hypocoagulation

  • Pneumothorax

  • Patent ductus arteriosus

• Etiology:	hypoxia with loss of autoregulation
  Pathogenesis:	rupture of friable vascular bed due to

  • fluctuating cerebral blood flow in preterm infants with respiratory distress

  • increase in cerebral blood flow with

    • systemic hypertension (pneumothorax, REM sleep, handling, tracheal suctioning, ligation of PDA, seizures, instillation of mydriatics)

    • rapid volume expansion (blood, colloid, hyperosmolar glucose / sodium bicarbonate)

    • hypercarbia (RDS, asphyxia)

  • increase in cerebral venous pressure with labor and delivery, asphyxia (= impairment in exchange of oxygen and carbon dioxide), respiratory disturbances

  • decrease in cerebral blood flow with systemic hypotension followed by reperfusion

  • platelet and coagulation disturbance

• Incidence:	in premature neonates <32 weeks of age; in 43% of infants <1,500 g (in 65% of 500 700 g infants, in 25% of 701 1,500 g infants); in up to 50% without prenatal care, in 5 10% with prenatal care
  Time of onset:	36% on first day, 32% on second day, 18% on first 3 day of life; by 6th day 91% of all intracranial bleeds have occurred
  Location:	region of the caudate nucleus and thalamostriate groove (= caudothalamic notch) remains metabolically active the longest; in 80 90% in infants <28 weeks of MA age

• GRADES (Papile classification):

  • I	:	subependymal hemorrhage confined to germinal matrix (GMH) on one / both sides
    II	:	subependymal hemorrhage ruptured into nondilated ventricle (IVH)
    III	:	intraventricular hemorrhage (IVH) with ventricular enlargement: (a) mild, (b) moderate, (c) severe
    IV	:	extension of germinal matrix hemorrhage into brain parenchyma (IPH)

• US (100% sensitivity + 91% specificity for lesions >5 mm; 27% sensitivity + 88% specificity for lesions 5 mm):

  • 1. Germinal matrix hemorrhage (grade I)

    • well-defined ovoid area of increased echogenicity (= fibrin mesh within clot) inferolateral to floor of frontal horn body of lateral ventricle

    • bulbous enlargement of caudothalamic groove anterior to termination of choroid plexus

      • DDx:

        choroid plexus (attached to inferomedial aspect of ventricular floor, tapers toward caudothalamic groove, never anterior to foramen of Monro)

    • resolving bleed develops central sonolucency

    • outcome: (1) complete involution (2) thin echogenic scar (3) subependymal cyst

  • 2. Mild intraventricular hemorrhage (grade II)

    • echogenic material filling a portion of lateral ventricles (acute phase) becoming sonolucent in a few weeks

    • clot may gravitate into occipital horns

    • vertical band of echogenicity between thalami on coronal scans (blood in 3rd ventricle)

    • irregular bulky choroid plexus (clot layered on surface of choroid plexus)

    • temporarily increased echogenicity of ventricular wall (= subependymal white halo between 7 days and 6 weeks after hemorrhagic event)

  • 3. Extensive intraventricular hemorrhage (grade III)

    • intraventricular cast of blood distending the lateral ventricles

    P.313

    
    

    • extension of hemorrhage into basal cisterns, cavum septi pellucidi

    • hemorrhage becomes progressively less echogenic

    • temporarily thickened echogenic walls of ventricles ( ventriculitis )

  • 4. Intraparenchymal hemorrhage (grade IV)

    • Cause:

      • extension of hemorrhage originating from germinal matrix (unusual)

      • separate hemorrhage within infarcted periventricular tissue (frequent)

    • Location:

      on side of largest amount of IVH, commonly lateral to frontal horns / in parietal lobe, rare in occipital lobe + thalamus

    • homogeneous highly echogenic intraparenchymal mass with irregular margins

    • central hypoechogenicity (liquefying hematoma after 10 14 days)

    • retracted clot settles to dependent position (3 4 weeks)

    • complete resolution by 8 10 weeks results in anechoic area (= porencephalic cyst)

  • Serial scans:

    5 10-day intervals

• CT:

  • Most sensitive + definite means to define site + extent of hemorrhage, especially in subdural hemorrhage, cerebral parenchymal hemorrhage, posterior fossa lesion

  • hyperdense bleed only visible up to 7 days before it becomes isodense

• Cx:

  • Posthemorrhagic hydrocephalus (30 70%)

    • Severity of hydrocephalus directly proportional to size of original hemorrhage!

    • Cause:

      • temporary blockage of arachnoid villi by particulate blood clot (within days), often transient with partial / total resolution

      • obliterative fibrosing arachnoiditis often in cisterna magna (within weeks); frequently leads to permanent progressive ventricular dilatation (50%)

    • thickened echogenic ventricular walls

    • Time of onset:

      by 14 days (in 80%)

    • delayed clinical signs because of compressible premature brain parenchyma

    • ventricular dilatation, particularly affecting the occipital horns (amount of compressible immature white matter is larger posteriorly)

    • DDx:

      ventriculomegaly secondary to periventricular cerebral atrophy (occurring slowly over several weeks)

  • Cyst formation

    • cavitation of hemorrhage

    • unilocular subependymal cyst

    • unilocular porencephalic cyst

  • Mental retardation, cerebral palsy

  • Death in 25% (IVH most common cause of neonatal death)

    • Prognosis:

      • Grade I + II: good with normal developmental scores (12 18% risk of handicap)

      • Grade III + IV: 54% mortality; 30 40% risk of handicap (spastic diplegia, spastic quadriparesis, intellectual retardation)

Choroid Plexus Hemorrhage

• affects primarily full-term infants

• Cause:

  birth trauma, asphyxia, apnea, seizures

• echogenicity of choroid plexus same as hemorrhage

• nodularity of choroid plexus

• enlargement of choroid plexus >12 mm in AP diameter

• left-right asymmetry >5 mm

• intraventricular hemorrhage without subependymal hemorrhage

• Cx:

  intraventricular hemorrhage (25%)

Intracerebellar Hemorrhage

• Cause:

  • full-term infant: traumatic delivery, intermittent positive pressure ventilation, coagulopathy

  • premature infant: subependymal germinal matrix hemorrhage up to 30 weeks gestation

• Incidence:

  16 21% of autopsies

• echogenicity of vermis same as hemorrhage

• echogenic mass in less echogenic cerebellar hemisphere (coronal scan most useful)

• nonvisualization / deformity of 4th ventricle

• asymmetry in thickness of paratentorial echogenicity is a sign of subarachnoid hemorrhage

• Prognosis:

  poor + frequently fatal

Intraventricular Hemorrhage

• Etiology:

  • germinal matrix hemorrhage ruptures through ependymal lining at multiple sites

  • bleeding from choroid plexus

• Route of hemorrhage: blood dissipates throughout ventricular system + aqueduct of Sylvius, passes through foramina of 4th ventricle, collects in basilar cistern of posterior fossa

• seizures, dystonia, obtundation, intractable acidosis

• bulging anterior fontanel, drop in hematocrit, bloody / proteinaceous CSF

• IVH usually cleared within 7 14 days

• Cx:	(1) Intracerebral hemorrhage
  	(2) Hydrocephalus

Periventricular Leukoencephalopathy

Periventricular Leukomalacia

• = PVL = perinatal hypoxic-ischemic encephalopathy

• = principal ischemic lesion of the premature infant characterized by focal coagulation necrosis of deep white matter as a result of ischemic infarction involving the watershed (= arterial border) zones between central and peripheral vascularity

• Vascular supply:

  • ventriculopetal branches penetrating cerebrum from pial surface are derived from MCA PCA ACA

  P.314

  
  

  • ventriculofugal branches extending from ventricular surface are derived from choroidal arteries striate arteries

• Incidence:

  • 7 22% at autopsy (88% of infants between 900 and 2,200 g surviving beyond 6 days); in 34% of infants <1,500 g; in 59% of infants surviving longer than 1 week on assisted ventilation; only 28% detected by cranial sonography

• Histo:

  edema, white matter necrosis, evolution of cysts + cavities / diminished myelin; nonhemorrhagic: hemorrhagic PVL = 3:1

• Pathogenesis:

  • immature autoregulation of periventricular vessels secondary to deficient muscularis of arterioles limits vasodilation in response to hypoxemia + hypercapnia + hypotension of perinatal asphyxia (hypoxic-ischemic encephalopathy)

• cerebral palsy (in 6.5% of infants <1,800 g):

  • spastic diplegia (81%) > quadriparesis (necrosis of descending fibers from motor cortex)

  • choreoathetosis, ataxia

  • mental retardation

• severe visual / hearing impairment

• convulsive disorders

• Location:

  bilateral white matter subjacent to external angle of lateral ventricular trigones, involving particularly the centrum semiovale (frontal horn + body), optic (occipital horn), and acoustic (temporal horn) radiations

• US (50% sensitivity + 87% specificity):

  • Early changes (2 days to 2 weeks after insult)

    • increased periventricular echogenicity (PVE) (DDx: echogenic periventricular halo / blush of fiber tracts in normal neonates, white matter gliosis, cortical infarction extending into deep white matter)

    • bilateral often asymmetric zones, occasionally extending to cortex

    • infrequently accompanied by IVH

  • Late changes (1 3 6 weeks after development of echodensities):

    • periventricular cystic PVL = cystic degeneration of ischemic areas (= multiple small never septated periventricular cysts in relationship to lateral ventricles; the larger the echodensities, the sooner the cyst formation)

    • brain atrophy secondary to thinning of periventricular white matter always at trigones, occasionally involving centrum semiovale

    • ventriculomegaly (after disappearance of cysts) with irregular outline of body + trigone of lateral ventricles

    • deep prominent sulci abutting the ventricles with little / no interposed white matter (DDx: schizencephaly)

    • enlarged interhemispheric fissure

• CT (not sensitive in early phase):

  • periventricular hypodensity (DDx: immature brain with increased water + incomplete myelination)

• MR (not sensitive in early phase):

  • hypointense areas on T1WI

  • hyperintense periventricular signals on T2WI in peritrigonal region

  • thinning of posterior body + splenium of corpus callosum (= degeneration of transcallosal fibers)

• Prognosis:

  • major neurologic problem / death in up to 62%; PVL localized to frontal lobes show relative normal development; generalized PVL results in neurologic deficits in close to 100%

• DDx:

  tissue damage from ventriculitis (sequelae of meningitis), metabolic disorders, in utero ischemia (eg, maternal cocaine abuse)

Periventricular Hemorrhagic Infarction

• = hemorrhagic necrosis of periventricular white matter, usually large + asymmetric

• Incidence:

  in 15 25% of infants with IVH

• Pathogenesis:

  • germinal matrix hemorrhage with intraventricular blood clot (in 80%)

  • ischemic periventricular leukomalacia leads to obstruction of terminal veins with sequence of venous congestion + thrombosis + infarction

• Histo:	perivascular hemorrhage of medullary veins near ventricular angle
  Associated with:	the most severe cases of intraventricular hemorrhage
  Age:	peak occurrence on 4th postnatal day

• spastic hemiparesis (affecting lower + upper extremities equally) / asymmetric quadriparesis (in 86% of survivors)

• Location:

  lateral to external angle of lateral ventricle on side of more marked IVH: 67% unilateral; 33% bilateral but asymmetric

• US:

  • Early changes (hours to days after major IVH):

    • unilateral / asymmetric bilateral triangular fan-shaped echodensities

    • extension from frontal to parieto-occipital regions / localized (particularly in anterior portion of lesion)

  • Late changes:

    • single large cyst = porencephaly

    • bumpy ventricle / false accessory ventricle

• Prognosis:

  59% overall mortality with echodensities >1 cm; in 64% major intellectual deficits

Encephalomalacia

• = more extensive brain damage than PVL; may include all of white matter in subcortex + cortex

• Associated with:

  • Neonatal asphyxia

  • Vasospasm

  • Inflammation of CNS

• US:

  • small ventricles (edema) with diffuse damage

  • increased parenchymal echogenicity making it difficult to define normal structures

  • decreased vascular pulsations

  P.315

  
  

  • transcranial Doppler:

    • group I (good prognosis)

      • normal flow profile, normal velocities, normal resistive index

    • group II (guarded prognosis)

      • increase in peak-systolic + end-diastolic flow velocities + decreased resistive index

    • group III (unfavorable prognosis)

      • reduced diastolic flow + decreased peak systolic and diastolic velocities + increased resistive index

    • ventricular enlargement + atrophy

    • extensive multicystic encephalomalacia with cysts often not communicating

Neuroblastoma

• Age at presentation:

  <2 years (50%); <4 years (75%); <8 years (90%); peak age <3 years

• abdominal mass (45%)

• neurologic signs (20%)

• bone pain / limp (20%)

• orbital ecchymosis / proptosis (12%)

• catecholamine production (95%) with paroxysmal episodes of flushing, tachycardia, hypertension, headaches, sweating, intractable diarrhea, acute cerebellar encephalopathy

• positive bone marrow aspiration (70%)

• Location:

  adrenal gland (67%), chest (13%), neck (5%), intracranial (2%); commonly involvement of multiple skeletal sites

• NUC (overall sensitivity of detection better than radiography):

  • CAVE:

    symmetric lytic neuroblastoma metastases occur frequently in metaphyseal areas where normal epiphyseal activity obscures lesions

  • purely lytic lesions may present as photopenic areas

  • soft-tissue uptake of Tc-99m phosphate in 60%

  • frequently Ga-67 uptake in primary site of neuroblastoma

• Prognosis:

  2-year survival (a) in 60% for age <1 year (b) in 20% for ages 1 2 years (c) in 10% for ages >2 years

• A. PRIMARY CEREBRAL NEUROBLASTOMA (rare)

  • Age:

    childhood / early adolescence

  • large hypodense / mixed-density mass with well-defined margins

  • intratumoral coarse dense calcifications

  • central cystic / necrotic zones with hemorrhage

  • Cx:

    metastasizes via subarachnoid space to dura + calvarium

• B. SECONDARY NEUROBLASTOMA (common)

  • metastatic to:

  • @ liver

  • @ skeleton

    • osteolysis with periosteal new-bone formation

    • sutural diastasis

    • hair-on-end appearance of skull

  • @ orbit:

    • unilateral proptosis

  • Neuroblastoma usually not metastatic to brain!

Olfactory Neuroblastoma

• = very malignant tumor arising from olfactory mucosa

• Types:

  • Esthesioneuroepithelioma

  • Esthesioneurocytoma

  • Esthesioneuroblastoma

• mass in superior nasal cavity with extension into ethmoid + maxillary sinuses

• Cx:

  distant metastases in 20%

Neurocutaneous Melanosis

• = rare sporadic congenital syndrome characterized by large multiple melanocytic nevi (in 5 15%) + melanotic lesions of CNS (in 40 60%)

• Age:	first 2 years of life (most); 2nd / 3rd decade (less commonly); M:F = 1:1
  Cause:	abnormal migration of melanocyte precursors, abnormal expression of melanin-producing genes within leptomeningeal cells, rapid proliferation of melanin-producing leptomeningeal cells
  Histo:	abnormal abundance of melanotic cells (which are normally found in basilar leptomeninges) with concomitant infiltration of perivascular spaces

• increased intracranial pressure

• seizures, ataxia, cranial nerve VI + VII palsies

• high attenuation of melanin pigments on CT scan

• hyperintense on T1WI, hypointense on T2WI (paramagnetic effect of oxygen-free radicals in melanin)

• leptomeningeal melanosis = foci of abnormally thickened leptomeninges

  • Location:

    inferior surface of cerebellum; inferior surface of frontal, temporal, occipital lobes; ventral aspect of pons, cerebra; peduncles, upper cervical spinal cord

• parenchymal melanosis (less common)

  • Location:

    cerebellum, anterior temporal lobes (esp. amygdala)

• frankly hemorrhagic necrotic invasive mass with transformation into malignant melanoma

• hydrocephalus

• posterior fossa cyst

• cerebellar hypoplasia

• Dandy-Walker malformation

• syringomyelia

• intraspinal arachnoid cyst

• intraspinal lipoma

• Prognosis:

  rapid deterioration + death within 3 years of diagnosis due to development of malignant melanoma / complication of hydrocephalus

Neurofibromatosis

• = autosomal dominant inherited disorder, probably of neural crest origin affecting all 3 germ cell layers, capable of involving any organ system

• Path:	frequently combination of
  	(1) pure neurofibromas (= tumor of nerve sheath with involvement of nerve, nerve fibers run through mass)
  	(2) neurilemmomas (= nerve fibers diverge and course over the surface of the tumor mass)
  	as (see SKULL AND SPINE DISORDERS)
  	(a) localized neurofibroma (most common, 90%)
  	(b) diffuse neurofibroma
  	mostly solitary + not associated with NF1
  	(c) plexiform neurofibroma
  	(PATHOGNOMONIC of NF1)
  	Often precedes development of cutaneous neurofibromas!

P.316




• Histo:

  proliferation of fibroblasts + Schwann cells

• More frequent involvement of deep large nerves (sciatic nerve, brachial plexus) in NF1 in contradistinction to isolated neurofibromas without NF1!

Peripheral Neurofibromatosis (90%)

• = NEUROFIBROMATOSIS TYPE 1 = NF1 = von Recklinghausen disease

• [Friedrich von Recklinghausen (1833 1910), pathologist in K nigsberg, W rzburg and Strassburg]

• = dysplasia of mesodermal + neuroectodermal tissue with potential for diffuse systemic involvement; autosomal dominant with abnormalities localized to the pericentromeric region of chromosome 17 (site of tumor suppressor gene neurofibromin); 50% spontaneous mutants; variable expressivity

  • mnemonic:	von Recklinghausen has 17 letters
    Incidence:	1:3,000; M:F = 1:1; all races
    	One of the most common genetic diseases and phakomatoses!

  • Predisposing factor:

    • advanced paternal age >35 years (2-fold increase in new mutations)

  • Diagnostic clinical criteria (at least two must be present):

    • 6 caf -au-lait spots

      • >5 mm in prepubertal individuals

      • >15 mm in postpubertal individuals

    • 2 neurofibromas of any type / 1 plexiform neurofibroma

    • axillary / inguinal freckling

    • optic pathway glioma

    • 2 Lisch nodules (= pigmented iris hamartomas)

    • characteristic skeletal lesion

      • sphenoid bone dysplasia

      • dysplasia + thinning of long bone cortex

    • 1st-degree relative (parent, sibling, child) with NF1

  • CLASSIC TRIAD:

    • Cutaneous lesions

    • Skeletal deformity

      • Musculoskeletal abnormalities predominate in NF1!

    • Mental deficiency

  • May be associated with:

    • MEA IIb (pheochromocytoma + medullary carcinoma of thyroid + multiple neuromas)

    • CHD (10 fold increase): pulmonary valve stenosis, ASD, VSD, IHSS

  • Cx:

    malignant transformation to malignant neurofibromas + malignant schwannomas (2 5 29%), glioma, xanthomatous leukemia

  • Rapid episodes of growth of neurofibromas:

    • puberty, pregnancy, malignancy

  • A. CNS MANIFESTATIONS

    • @ Intracranial

      • Optic pathway glioma

        • isolated to single optic nerve extension to other optic nerve, chiasm, optic tracts

        • Age:	<6 years; M:F = 1:2
          Histo:	pilocytic astrocytoma with perineural / subarachnoid spread (optic nerve is embryologically part of hypothalamus and develops gliomas instead of schwannomas)

        • The most common tumor in up to 15 21% of all neurofibromatosis patients

        • 10% of all optic nerve gliomas are associated with neurofibromatosis

      • Cerebral gliomas

        • astrocytomas of tectum, brainstem, gliomatosis cerebri (= unusual confluence of astrocytomas)

      • Hydrocephalus

        • obstruction usually at aqueduct of Sylvius

        • Cause:

          benign aqueductal stenosis, glioma of tectum / tegmentum of mesencephalon

      • Vascular dysplasia

        • = occlusion / stenosis of distal internal carotid artery, proximal middle / anterior cerebral artery

        • moyamoya phenomenon (60 70%)

      • Neurofibromas (= arising from Schwann cells + fibroblasts) of cranial nerves III XII (most commonly V + VIII)

        • 30% of patients with solitary neurofibromas have NF1

        • Virtually all patients with multiple neurofibromas have NF1

      • Craniofacial plexiform neurofibromas

        • = locally aggressive congenital lesion composed of tortuous cords of Schwann cells, neurons + collagen with progression along nerve of origin (usually small unidentified nerves)

        • Location:

          commonly orbital apex, superior orbital fissure

        • Plexiform neurofibromas are PATHOGNOMONIC for NF1

      • CNS hamartomas (up to 75 90%)

        • = probably dysmyelinating lesions (may resolve)

        • Location:

          pons, basal ganglia (most commonly in globus pallidus), thalamus, cerebellar white matter

        • multiple foci of isointensity on T1WI + hyperintensity on T2WI without mass effect (= unidentified bright objects )

      • Vacuolar / spongiotic myelinopathy (in 66%)

        • Location:

          basal ganglia (esp. in globus pallidus), cerebellum, internal capsule, brainstem

        • nonenhancing hyperintense foci on T2WI

      • @ Spinal cord

        • Cord neurofibroma

          • smooth round / tubular masses of varying sizes at nearly every level throughout the spinal canal

          • spinal cord displaced to contralateral side

          • enlargement of neural foramen due to dumbbell neurofibroma of spinal nerves (in 30%)

          P.317

          
          

          • smooth fusiform / spherical mass:

            • hypoattenuating mass (20 30 HU) in up to 73% due to cystic degeneration, xanthomatous features, confluent areas of hypocellularity, lipid-rich Schwann cells

            • areas of higher attenuation due to densely cellular components / collagen-rich regions

            • slightly hyperintense to muscle on T1WI, hyperintense periphery + hypointense core on T2WI

            • hypoechoic heterogeneous well-circumscribed cylindrical lesion with variable through transmission

          • Paraspinal / presacral neurofibroma

            • Location:

              adjacent to psoas muscle at single / multiple vertebral body levels in distribution of lumbosacral plexus

          • heterogeneous echotexture with variable through transmission

          • smooth round / tubular symmetric / asymmetric paraspinal masses:

            • homogeneously hypoattenuating (20 25 HU) in up to 73% due to myxoid and mucinous stroma

            • focal areas of higher attenuation due to excessive collagen

            • homo- / heterogeneous enhancement to 30 50 HU on CECT in 50%

          • enlargement of adjacent neural foramen in 30%

        • Lateral / anterior intrathoracic meningocele

          • = diverticula of thecal sac extending through widened neural foramina / defects in vertebra

          • Cause:	dysplasia of meninges focally stretched by CSF pulsations (due to pressure differences between thorax + subarachnoid space superimposed on bone vertebral defect)
            Location:	thoracic level (most common)

          • erosion of bony elements with marked posterior scalloping

          • widening of neural foramina (due to protrusion of spinal meninges)

          • DDx:

            mediastinal / lung abscess

    • B. SKELETAL MANIFESTATIONS (in 25 40%)

      • dwarfism caused by scoliosis

      • @ Orbit

        • Harlequin appearance to orbit = partial absence of greater and lesser wing of sphenoid bone + orbital plate of frontal bone (failure of development of membranous bone)

        • hypoplasia + elevation of lesser wing of sphenoid

        • defect in sphenoid bone extension of middle cranial fossa structures into orbit

        • concentric enlargement of optic foramen (optic glioma)

        • enlargement of orbital margins + superior orbital fissure (plexiform neurofibroma of peripheral and sympathetic nerves within orbit / optic nerve glioma)

        • sclerosis in the vicinity of optic foramen (optic nerve sheath meningioma)

        • deformity + decreased size of ipsilateral ethmoid + maxillary sinus

      • @ Skull

        • macrocranium + macroencephaly

        • left-sided calvarial defect adjacent to lambdoid suture = parietal mastoid (rare)

      • @ Spine

        • sharply angled focal kyphoscoliosis (50%) in lower thoracic + lumbar spine; kyphosis predominates over scoliosis; incidence increases with age

          • Cause:

            abnormal development of vertebral bodies

        • hypoplasia of pedicles, transverse + spinous processes

        • posterior scalloping of vertebral bodies due to dural ectasia (secondary to weakened meninges allowing transmission of normal CSF pulsations)

        • dumbbell-shaped enlargement of neural foramina

      • @ Appendicular skeleton

        • anterolateral bowing of lower half of tibia (most common) / fibula (frequent) / upper extremity (uncommon) secondary to deossification

        • pseudarthrosis after bowing fracture (particularly in tibia) in 1st year of life

        • atrophic thinned / absent fibulas

        • periosteal dysplasia = traumatic subperiosteal hemorrhage with abnormal easy detachment of periosteum from bone

        • subendosteal sclerosis

        • bone erosion from periosteal / soft-tissue neurofibromas

        • intramedullary longitudinal streaks of increased density

        • multiple nonossifying fibromas / fibroxanthomas

        • single / multiple cystic lesions within bone (? deossification / nonossifying fibroma)

        • focal gigantism = unilateral overgrowth of a limb bone; marked enlargement of a digit in a hand / foot (overgrowth of ossification center)

      • C. PULMONARY MANIFESTATIONS

        • @ Lung

          • exertional dyspnea

          • intrathoracic lateral + anterior meningoceles

          • peripheral pulmonary nodule = pedunculated intercostal neurofibromas

          • progressive pulmonary interstitial fibrosis with lower lung field predominance (in up to 20%)

          • large thin-walled bullae with asymmetric upper lobe predominance

        • @ Mediastinum

          • Neurogenic tumors account for 9% of primary mediastinal masses in adults + 30% in children

          • mediastinal masses:

            • well-marginated smooth round / elliptic mass

            • extensive fusiform / infiltrating mass

          • paravertebral neurofibromas

        • @ Chest wall

          • numerous small well-defined subcutaneous neurofibromas

          P.318

          
          

          • twisted ribbonlike ribs in upper thoracic segments due to bone dysplasia / multiple neurofibromas of intercostal nerves:

            • localized cortical notches / depression of inferior margins of ribs (DDx: aortic coarctation)

          • chest wall mass invading / eroding / destroying adjacent ribs

        • D. NEURAL CREST TUMORS

          • Pheochromocytoma:

            • hypertension in adults (in children with NF1 more commonly associated with vasculopathy)

            • solitary + unilateral (in 84%)

            • bilateral (in 10%)

            • extraadrenal (in 6%)

          • Parathyroid adenomas:

            • hyperparathyroidism

        • D. VASCULAR LESIONS

          • = Schwann cell proliferation within vessel wall

          • 1. Cranial artery stenosis

          • 2. Renal artery stenosis: very proximal, funnel-shaped (one of the most common causes of hypertension in childhood)

          • 3. Renal artery aneurysm

          • 4. Thoracic / abdominal aortic coarctation

        • E. GI TRACT MANIFESTATIONS (10 25%)

          • Neurofibroma

            • mostly clinically occult

            • intestinal bleeding (hematemesis, melena, hematochezia) with mucosal involvement

            • obstruction with nausea, vomiting, abdominal distension (intussusception, volvulus, simulating Hirschsprung disease with plexiform neurofibromas of colon)

            • Location:	jejunum > stomach > ileum > duodenum; retroperitoneal / paraspinal
              Site:	mesenteric, subserosal, myenteric plexuses
              Associated with:	increased prevalence of carcinoid tumors + GI stromal tumors

            • (a) solitary pattern = single neurofibroma, neuroma, ganglioneuroma, schwannoma

              • subserosal / submucosal filling defect ( mucosal ganglioneurofibromatosis )

              • displacement of intestine

              • external mass effect on serosal surface

              • infiltrating submucosal / mucosal polypoid masses

              • mural thickening of soft-tissue attenuation with variable amount of luminal narrowing

            • (b) plexiform pattern = regional enlargement of nerve root trunks

              • mass effect on adjacent barium-filled loops

              • multiple eccentric polypoid filling defects involving mesenteric side of small bowel

              • mesenteric fat trapped within entangled network (15 30 HU) CHARACTERISTIC

              • multiple leiomyomas ulcer

              • well-defined homo- or heterogeneous hypoechoic masses

              • iso- or hypoattenuating masses

            • Cx:

              intussusception

          • Malignant peripheral nerve sheath tumor

            • most common malignant abdominal tumor in NF1

          • Ganglioneuroma

          • Carcinoid

            • more common in NF1 than in general population

            • Location:	near ampulla of Vater
              Histo:	psammomatous somatostatinoma

          • Gastrointestinal stromal tumor

        • F. GENITOURINARY MANIFESTATIONS (rare)

          • Renal artery stenosis

            • plexiform neurofibroma with vascular narrowing

          • Urinary bladder mass

            • Origin:

              vesicoprostatic (male) / urethrovaginal neural plexus (female)

            • symptoms of urinary tract obstruction: frequency, urgency, incontinence, hematuria, abdominal pain

            • solitary hypoechoic bladder wall mass

            • diffuse bladder wall thickening; mass may surround uterus, vagina, sigmoid colon

            • scalloped contour of urinary bladder

            • Cx:

              hydronephrosis

        • G. OCULAR MANIFESTATIONS (6%)

          • pulsatile exophthalmos / unilateral proptosis (herniation of subarachnoid space + temporal lobe into orbit)

          • buphthalmos

          • 1. Plexiform neurofibroma (most common)

          • 2. Lisch nodules

            • = melanocytic iris hamartomas <2 mm in size

            • yellow / brown pigmented nodular elevations projecting from surface of iris; mostly bilateral

            • asymptomatic

            • Age:

              appear in childhood; >20 years of age in >90%

          • 3. Optic glioma: in 12% of patients, in 4% bilateral; 75% in 1st decade

            • extension into optic chiasm (up to 25%), optic tracts + optic radiation

            • increased intensity on T2WI if chiasm + visual pathways involved

          • 4. Perioptic meningioma

          • 5. Choroidal hamartoma: in 50% of patients

      • H. SKIN MANIFESTATIONS

        • Caf -au-lait spots

          • = pigmented cutaneous macules 6 in number >5 mm in greatest diameter prior to puberty>15 mm in postpubertal individuals

          • often ovoid

          • coast of California type (= smooth outline)

          • Age:	during 1st year of life / may be present at birth
            	One of the earliest manifestations of NF1

          • Histo:	increased melanin pigment in basal epidermal layer
            DDx:	tuberous sclerosis, fibrous dysplasia
            Extent:	often parallels disease severity

        • Freckling

          • = pigmented cutaneous macules <5 mm in size

          • Age:	3 5 years
            Location:	intertriginous skin of axilla (in 66%), groin, submammary fold, neck

        • Dermal (cutaneous) neurofibroma

          P.319

          
          

          • Age:

            begin to appear around early childhood / puberty subsequent to detection of caf -au-lait spots

          • (a) localized = fibroma molluscum = string of pearls along peripheral nerve

            • firm well-circumscribed movable tumor

            • soft compressible

            • Cx:

              NO malignant degeneration!

          • (b) plexiform neurofibroma = multilobulated tortuous entanglement / interdigitating network of tumor along a nerve + its branches

            • Exclusively seen in NF1

            • soft gritty often hyperpigmented tumor feeling like a bag of worms / braided ropes

            • may become very large hanging in a pendulous fashion associated with massive disfiguring enlargement of an extremity (= elephantiasis neuromatosa)

            • osseous hypertrophy (due to chronic hyperemia)

            • Cx:

              May transform to malignant peripheral nerve sheath tumor (MPNST)!

Neurofibromatosis with Bilateral Acoustic Neuromas

• = NEUROFIBROMATOSIS TYPE 2 = NF2 = CENTRAL NEUROFIBROMATOSIS

• = rare autosomal dominant syndrome characterized by propensity for developing multiple schwannomas, meningiomas, and gliomas of ependymal derivation

  • mnemonic:

    MISME

    • Multiple Inherited Schwannomas

    • Meningiomas

    • Ependymomas

• Incidence:	1:50,000 births
  Etiology:	deletion on the long arm of chromosome 22; in 50% new spontaneous mutation
  	Neurofibromatosis 2 is located on chromosome 22!
  Symptomatic age:	during 2nd / 3rd decade of life

• Diagnostic criteria:

  • bilateral 8th cranial nerve masses

  • first-degree relative with unilateral 8th nerve mass, neurofibroma, meningioma, glioma (spinal ependymoma), schwannoma, juvenile posterior subcapsular lenticular opacity

• NO Lisch nodules, skeletal dysplasia, optic pathway glioma, vascular dysplasia, learning disability

• caf -au-lait spots (<50%): pale, <5 in number

• cutaneous neurofibroma: minimal in size + number / absent

• @ Intracranial

  • Bilateral acoustic schwannomas (sine qua non)

    • Site:

      superior / inferior division of vestibular n.

    • usually asymmetric in size

  • Schwannoma of other cranial nerves

    • Frequency:

      trigeminal n. > facial n.

    • Nerves without Schwann cells are excluded: olfactory nerve, optic nerve

  • Multiple meningiomas: intraventricular in choroid plexus of trigone, parasagittal, sphenoid ridge, olfactory groove, along intracranial nerves

  • Meningiomatosis = dura studded with innumerable small meningiomas

  • Glioma of ependymal derivation

• @ Spinal

  • symptoms of cord compression

  • A. Extramedullary

    • Multiple paraspinal neurofibromas

    • Meningioma of spinal cord (thoracic region)

  • Intramedullary

    • Spinal cord ependymomas

Neuroma

• Prevalence:	8% of all intracranial tumors
  Age:	20 50 years

• slow growth; not painful

Vestibular Schwannoma

• = ACOUSTIC NEUROMA = ACOUSTIC SCHWANNOMA

  • = NEURILEMMOMA

• Most common neoplasm of internal auditory canal / cerebellopontine angle!

• Prevalence:	6 10% of all intracranial tumors; 85% of all intracranial neuromas; 60 90% of all cerebellopontine angle tumors
  Age:	(a) sporadic tumor: 35 60 years; M:F = 1:2
  	(b) type 2 neurofibromatosis: 2nd decade

• Histo:

  • encapsulated neoplasm composed of proliferating fusiform Schwann cells with

    • highly cellular dense regions (Antoni A) with reticulin + collagen, and

    • loose areas with widely separated cells (Antoni B) in a reticulated myxoid matrix; common degenerative changes with cyst formation, vascular features, lipid-laden foam cells

  • May be associated with:

    central neurofibromatosis

    • Solitary intracranial schwannoma is associated with type 2 neurofibromatosis in 5 25%!

    • Bilateral acoustic schwannomas allow a presumptive diagnosis of type 2 neurofibromatosis!

  • long history of slowly progressive unilateral sensorineural hearing loss affecting high-frequency sounds more severely (in 95%)

  • tinnitus, pain

  • diminished corneal reflex

  • unsteadiness, vertigo, ataxia, dizziness (<10%)

  • Doubling time:

    2 years

  • Location:

    • arises from within internal auditory canal (IAC) in 80% / cochlea

    • may arise in cerebellopontine angle cistern at opening of IAC (= porus acusticus) with intracanalicular extension in 5%

  • Site:

    • in 85% from the vestibular portion of 8th nerve (around vestibular ganglion of Scarpa / at the glial-Schwann cell junction) posterior to cochlear portion

    • in 15% from the cochlear portion

  • round mass centered on long axis of IAC forming acute angles with dural surface of petrous bone

  P.320

  
  

  • funnel-shaped component extending into IAC

  • IAC enlargement / erosion (70 90%)

  • widening / obliteration of ipsilateral cerebellopontine angle cistern

  • shift / asymmetry of 4th ventricle with hydrocephalus

  • degenerative changes (cystic areas hemorrhage) with tumors >2 3 cm

  • Plain film:

    • flaring porus acusticus

    • erosion of IAC: a difference in canal height of >2 mm is abnormal + indicates a schwannoma in 93%

  • CT:

    • isodense small / hypodense large solid tumor

    • cyst formation in tumor (= central necrosis in 15% of large tumors) / coexistent extramural arachnoid cyst adjacent to tumor

    • usually uniformly dense tumor enhancement with small tumors (50% may be missed without CECT) / ring enhancement with large tumors

    • NO calcification

    • intrathecal contrast / carbon dioxide insufflation (for tumors <5 mm)

  • MR (most sensitive test with Gd-DTPA enhancement):

    • iso- / slightly hypointense on T1WI relative to brain

    • intensely enhancing homogeneous mass / ringlike enhancement (if cystic) after Gd-DTPA

    • hyperintense on T2WI (DDx: meningioma remains hypo- / isointense)

  • Angio:

    • elevation + posterior displacement of anterior inferior cerebellar artery (AICA) on basal view

    • elevation of the superior cerebellar artery (large tumors)

    • displacement of basilar artery anteriorly / posteriorly + contralateral side

    • compression / posterior + lateral displacement of petrosal vein

    • posterior displacement of choroid point of PICA

    • vascular supply frequently from external carotid artery branches

    • rarely hypervascular tumor with tumor blush

    • DDx:

      ossifying hemangioma (bony spiculations)

Trigeminal Neuroma

• = TRIGEMINAL SCHWANNOMA

• Incidence:	2 5% of intracranial neuromas, 0.26% of all brain tumors
  Origin:	arising from gasserian ganglion within Meckel cave at the most anteromedial portion of the petrous pyramid / trigeminal nerve root
  Age:	35 60 years; M:F = 1:2

• Symptoms of location in middle cranial fossa:

  • facial paresthesia / hypesthesia

  • exophthalmos, ophthalmoplegia

• Symptoms of location in posterior cranial fossa:

  • facial nerve palsy

  • hearing impairment, tinnitus

  • ataxia, nystagmus

• Location:

  (in any segment of trigeminal nerve)

  • middle cranial fossa (46%) = gasserian ganglion

  • posterior cranial fossa (29%)

  • in both fossae (25%)

  • pterygoid fossa / paranasal sinuses (10%)

• erosion of petrous tip

• enlargement of contiguous fissures, foramina, canals

• dumbbell / saddle-shaped mass (extension into middle cranial fossa + through tentorial incisura into posterior fossa)

• isodense mass with dense inhomogeneous enhancement (tumor necrosis + cyst formation)

• distortion of ipsilateral quadrigeminal cistern

• displacement + cutoff of posterior 3rd ventricle

• anterior displacement of temporal horn

• angiographically avascular / hypervascular mass

Oligodendroglioma

• = uncommon form of slowly growing glioma; presenting with large size at time of diagnosis

• Incidence:	5 18% of all glial neoplasms; 2 5% of all primary brain tumors
  Histo:	mixed glial cells (50%), astrocytic components (30%); microcalcifications (90%); mucoid / cystic degeneration (frequent); hemorrhage infrequent (DDx: central neurocytoma)
  Age:	30 50 years; adult:child = 8:1; M>F
  	Older age is associated with more aggressive tumor behavior!

• long clinical presentation >5 years

• seizures (35 85%), headache, mental status change

• paralysis (50%), visual loss (49%), papilledema (47%)

  • Worse prognosis with neurologic deficit!

• ataxia (39%), abnormal reflexes (37%), meningismus

• Location:	frontal lobe (50 65%); temporal lobe (47%); parietal lobe (7 20%); occipital lobe (1 4%); cerebellum (3%); brainstem & spinal cord (1%); leptomeninges ( oligodendrogliomatosis ); cerebellopontine angle; cerebral ventricles (3 8%) = subependymal oligodendroglioma ; retina; optic nerve
  Site:	most commonly involving cortex + subcortical white matter; occasionally through corpus callosum as butterfly glioma

• large nodular clumps of calcifications (in 45% on plain film; in 20 91% on CT)

• CT:

  • round / oval hypodense (60%) / isodense (23%) / hyperdense (6%) sharply marginated mass

  • cystic degeneration and hemorrhage (uncommon)

  • erosion of inner table of skull

  • May not be detectable at all by CT!

• CECT:

  • subtle ill-defined enhancement (15 20%) associated with higher-grade tumor

  • may be adherent to dura (mimicking meningiomas)

  • edema (in 50% of low-grade, in 80% of high-grade tumors)

• MR:

  • well-circumscribed tumor of heterogeneous intensity:

    • hypo- / isointense compared to gray matter on T1WI

    • hyperintense on T2WI

    • water restriction on DWI in high-grade tumors (from lowered extracellular hyaluronic acid) + higher ADC values in low-grade tumors

  P.321

  
  

  • little edema / mass effect (common)

  • solid / peripheral / mixed moderate enhancement

  • calcification may not be detected

• SPECT (Tl-201) & PET (C-11 L-methylmethionine):

  • metabolic rate correlates with histologic grade

  • detects hypermetabolic regions within tumor

• Cx:	leptomeningeal seeding via CSF (1 15%)
  Rx:	gross total resection; PCV chemotherapy (procarbazine, lomustine, vincristine); irradiation reserved for chemotherapy failure
  Prognosis:	46% 10-year survival rate with low-grade;
  	20% 10-year survival rate with high-grade;
  	3 17 years median postop survival

• DDx:	(1)	Astrocytoma (no large calcifications)
  	(2) Ganglioglioma (in temporal lobes + deep cerebral tissues
  	(3) Ependymoma (enhancing tumor, often with internal bleeding producing fluid levels)
  	(4) Glioblastoma (infiltrating, enhancing, edema, no calcifications)

Paragonimiasis of Brain

• = Oriental lung fluke (Paragonimus westermani) producing arachnoiditis, parenchymal granulomas, encapsulated abscesses

• isodense / inhomogeneous masses surrounded by edema

• ring enhancement

Pelizaeus-Merzbacher Disease

• = rare X-linked sudanophilic leukodystrophy (5 types with different times of onset, rate of progression, genetic transmission)

• Age:

  neonatal period

• bizarre pendular nystagmus + head shaking

• cerebellar ataxia

• slow psychomotor development

• CT:

  • hypodense white matter

  • progressive white matter atrophy

• MR:

  • lack of myelination (appearance of newborn retained)

  • hyperintense internal capsule, optic radiations, proximal corona radiata on T1WI

  • near complete absence of hypointensity in supratentorial region on T2WI

  • mild / moderate prominence of cortical sulci

• Prognosis:

  death in adolescence / early adulthood

Pick Disease

• = rare form of presenile dementia similar to Alzheimer disease; may be inherited with autosomal dominant mode; M < F

• focal cortical atrophy of anterior frontal + anterior temporal lobes

• dilatation of frontal + temporal horns of lateral ventricle

Pineal Cyst

• = small nonneoplastic cyst of pineal gland

• Incidence:

  25 40% on autopsy, 4% on MRI

• Types:

  • developmental = persistence of ependymal-lined pineal diverticulum

  • degenerative = glial-lined secondary cavitation within area of gliosis

• never associated with Parinaud syndrome

• rarely cause of hydrocephalus (compression / occlusion of aqueduct)

• may be symptomatic when large

  • calcification

• CT:

  • normal-sized gland (80%), slightly >1 cm in 20%, can be >2 cm in size

  • isodense to CSF in surrounding cistern (infrequently noted)

• MR:

  • sharply marginated ovoid mass in pineal region

  • slight impression on superior colliculi (sagittal image)

  • isointense to CSF on T1WI + slightly hyperintense to CSF on T2WI (due to phase coherence in cysts but not in moving CSF)

  • may have higher signal intensity than CSF due to high protein content

  • contrast may diffuse from enhanced rim of residual pineal tissue into fluid center (no blood-brain barrier) on delayed sequence images

• Prognosis:

  lack of growth over long time

Pineal Germinoma

• = DYSGERMINOMA = PINEALOMA = ATYPICAL TERATOMA (former inaccurate names)

  • pinealoma = misnomer referring to any pineal mass

• = malignant primitive germ cell neoplasm

• Incidence:	most common pineal tumor (>50% of all pineal tumors, 66% of pineal germ cell tumors)
  Histo:	identical to testicular seminoma + ovarian dysgerminoma, NO capsule facilitates invasion
  Age:	10 25 years; M:F = 10:1 to 33:1
  May be associated with:	ectopic pinealoma = secondary focus in inferior portion of 3rd ventricle

• precocious puberty frequent in children <10 years of age

• Parinaud syndrome = paralysis of upward gaze (compression of mesencephalic tectum)

• Location of germinomas:

  pineal gland (80%), suprasellar region (20%), basal ganglia, thalamus

• displacement of calcified pineal gland

• hydrocephalus (compression of aqueduct of Sylvius)

• well-defined lesion restricted to pineal gland

• may infiltrate quadrigeminal plate / thalamus

• CT:

  • infiltrating variodense / frequently hyperdense homogeneous mass (attenuation usually similar to gray matter)

  • rarely psammomatous calcifications within tumor, but pineal calcifications in 100% (40% in normal population)

  • moderate / marked uniform contrast enhancement

• MR:

  • round / lobular well-circumscribed relatively homogeneous mass isointense to gray matter:

    • intermediate intensity on T1WI

    • slightly hypointense mass on T2WI (occasionally)

  • strong Gd-DTPA enhancement

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• Cx:	CSF seeding (frequent, CSF cytology more sensitive than imaging, contrast MR of entire neuroaxis)
  Rx:	combination of irradiation (very radiosensitive) + chemotherapy (doxorubicin, cisplatin, cyclophosphamide)
  Prognosis:	75% survival after radiation therapy alone

Pineal Teratocarcinoma

• = highly malignant variant of germ cell tumors

• Types:

  • Choriocarcinoma

  • Embryonal cell carcinoma

  • Endodermal sinus tumor

• Histo:	arising from primitive germ cells, frequently containing more than one cell type
  Age:	<20 years; males

• Parinaud syndrome

• tumor markers elevated in serum + CSF

• intratumoral hemorrhage (esp. choriocarcinoma)

• invasion of adjacent structures

• intense homogeneous contrast enhancement

• Cx:

  seeding via CSF

Pineal Teratoma

• = benign tumor containing one / all three germ cell layers (pineal region most common site of teratomas)

• Incidence:	15% of all pineal masses (2nd most common tumor in pineal region)
  Age:	<20 years; M:F = 2:1 to 8:1

• Parinaud syndrome = paralysis of upward gaze (compression / infiltration of superior colliculi)

• hypothalamic symptoms

• headache

• somnolence (related to hydrocephalus)

• Location:

  pineal, parapineal, suprasellar, 3rd ventricle

• well-defined rounded / irregular lobulated extremely heterogeneous mass of fat, cartilage, hair, linear / nodular calcifications + cysts

  • Fat is absent in all other pineal tumors!

• may show heterogeneous / rimlike contrast enhancement (limited to solid-tissue areas)

• Angio:

  • elevation of internal cerebral vein

  • posterior displacement of precentral vein

• CT:

  • heterogeneous mass with fat, calcification, cystic + solid areas

• MR:

  • variegated appearance on all pulse sequences:

  • hyperintense areas of fat on T1WI with chemical shift artifact

• Cx:

  chemical meningitis with spontaneous rupture

Pineal Cell Tumors

• similar imaging appearance

• peripherally displaced preexisting normal pineal calcification (= exploded pineal pattern )

Pineoblastoma

• = highly malignant tumor derived from primitive pineal parenchymal cells

• Histo:	unencapsulated highly cellular primitive small round cell tumor (similar to medulloblastoma, neuroblastoma, retinoblastoma)
  Age:	any age, more common in children; M < F

• usually large mass

• CT:

  • poorly marginated iso- / slightly hyperdense mass

  • may contain dense tumor calcifications

  • intense homogeneous contrast enhancement

• MR:

  • iso- / moderately hypointense on T1WI + iso- / hyperintense on T2WI

  • dense homogeneous Gd-DTPA enhancement

• Spread:

  • direct extension posteriorly with invasion of cerebellar vermis + anteriorly into 3rd ventricle

  • CSF seeding (frequent) along meninges / via ventricles

Pineocytoma

• = rare slow-growing unencapsulated tumor composed of mature pineal parenchymal cells

• Age:

  any age; M:F = 1:1

  • small tumor

  • CT:

    • well-marginated slightly hyperdense / isodense mass

    • dense focal tumor calcifications possible

    • well-defined marked homogeneous enhancement

  • MR:

    • intermediate intensity on T1WI + T2WI

    • may be isointense to CSF but containing trabeculations (DDx to pineal cyst)

    • mild to moderate Gd-DTPA enhancement

  • Cx:

    some metastasize via CSF

Pituitary Adenoma

• = benign slow-growing neoplasm arising from adenohypophysis (= anterior lobe); most common tumor of adenohypophysis

• Prevalence:	5 10 18% of all intracranial neoplasms;
  	<3% of patients have underlying MEN 1

• pituitary hyperfunction / hypofunction / visual field defect

• Plain film: (UNRELIABLE !)

  • enlargement of sella + sloping of sella floor

  • erosion of anterior + posterior clinoid processes

  • erosion of dorsum sellae

  • calcification in <10%

  • may present with mass in nasopharynx

• CECT (thin section SAG + COR with dynamic bolus injection):

  • upward convexity of gland

  • increased height >10 mm

  • deviation of pituitary stalk (nonspecific + unreliable)

  • erosion of floor of sella

  • gland asymmetry

  • focal hypodensity (most specific for adenoma) before + after IV contrast administration

  • shift of pituitary tuft / density change in region of adenoma

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• MR (thin-section SAG + COR with small field of view):

  • highest sensitivity on coronal nonenhanced T1WI (70%) + 3-D FLASH sequence (69%) + combination of both (90%)

  • 1/3 of lesions are missed with enhancement

  • 1/3 of lesions are missed without enhancement

  • focus of low signal intensity on T1WI

  • focus of high-signal intensity on T2WI

  • focal hypointensity within normally enhancing gland

• DDx:

  simple pituitary cyst (= Rathke cleft cyst)

Functioning Pituitary Adenoma

• Adenoma may secrete multiple hormones!

  • PROLACTINOMA (30%)

    • most common of pituitary adenomas; approximately 50% of all cranial tumors at autopsy; M << F

    • prolactin levels do not closely correlate with tumor size

    • Any mass compressing the hypothalamus / pituitary stalk diminishes the tonic inhibitory effect of dopaminergic factors, which originate there, resulting in hyperprolactinemia!

    • Female:

      • Age:

        15 44 years (during childbearing age)

      • infertility

      • amenorrhea

      • galactorrhea

      • elevated prolactin levels (normal <20 ng/mL)

      • >75% of patients with serum prolactin levels >200 ng/mL will show a pituitary tumor!

    • Male:

      • headache

      • impotence + decreased libido

      • visual disturbance

    • characteristic lateral location, anteriorly / inferiorly; variable in size

    • Rx:

      bromocriptine

  • CORTICOTROPHIC ADENOMA (14%)

    • Function:	ACTH-secreting tumor
      Age:	30 40 years; M:F = 1:3

    • Cushing disease

    • central location; posterior lobe; usually <5 mm in size

    • sampling of inferior petrosal sinuses (95% diagnostic accuracy compared with 65% for MRI)

    • Rx:	(1)	suppression by high doses of dexamethasone of 8 mg/day
      	(2) surgical resection difficult because ACTH adenomas usually require resection of an apparently normal gland (tumor small + usually not on surface)

    • SOMATOTROPHIC ADENOMA (14%)

      • gigantism, acromegaly, elevated GH >10 ng/mL, no rise in GH after administration of glucose / TRH

      • Histo:	(a) densely granulated type
        	(b) sparsely granulated type: clinically more aggressive

      • hypodense region, may be less well-defined, variable size

    • GONADOTROPH CELL ADENOMA (7%)

      • secretes follicle-stimulating hormone (FSH) / luteinizing hormone (LH)

      • slow-growing often extending beyond sella

    • THYROTROPH CELL ADENOMA (<1%)

      • secretes thyroid-stimulating hormone (TSH)

      • often large + invasive pituitary adenoma

    • PLURIHORMONAL PITUITARY ADENOMA (>5%)

Nonfunctioning Pituitary Adenoma

• NULL CELL ADENOMA

  • = hormonally inactive pituitary tumor with no histologic / immunologic / ultrastructural markers to indicate its cellular derivation

  • Prevalence:	17% of all pituitary tumors
    Age:	older patient

  • slow-growing

• ONCOCYTOMA

  • Prevalence:

    10% of all pituitary tumors

  • clinically + morphologically similar to null cell adenoma

Pituitary Macroadenoma

• = tumor >10 mm in size

• Incidence:	10% (70 80% of pituitary adenomas); M:F = 1:1
  Age:	25 60 years

• symptoms of mass effect: hypopituitarism, bitemporal hemianopia (with superior extension), pituitary apoplexy, hydrocephalus, cranial nerve involvement (III, IV, VI)

• usually endocrinologically inactive

• Extension into:

  suprasellar cistern / cavernous sinus / sphenoid sinus + nasopharynx (up to 67% are invasive)

• occasionally tumor hemorrhage

• lucent areas correspond to cysts / focal necrosis

• invasion of cavernous sinus: encasement of carotid artery (surest sign)

• CT:

  • tumor isodense to brain tissue

  • erosion of bone (eg, floor of sella)

  • calcifications infrequent

• MR: (allows differentiation from aneurysm)

  • homogeneous enhancement

• Cx:

  • Obstructive hydrocephalus (at foramen of Monro)

  • Encasement of carotid artery

  • Pituitary apoplexy (rare)

• DDx:

  • Metastasis (more bone destruction, rapid growth)

  • Pituitary abscess

Pituitary Microadenoma

• = very small adenomas <10 mm

• usually become clinically apparent by hormone production (20 30% of all pituitary adenomas)

• Prolactin elevation (>25 ng/mL in females)

  • 4 8 normal:	adenoma demonstrated in 71%
    >8 normal:	adenoma demonstrated in 100%

• incidentaloma = nonfunctioning microadenoma / pituitary cyst

• NO imaging features to distinguish between different types of adenomas

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• MRI:

  • small nonenhancing mass of hypointensity on pre- and postcontrast T1WI

  • occasionally isointense on precontrast images + hyperintense on postcontrast images

  • enhancement on delayed images

  • focal bulge on surface of gland

  • focal depression of sellar floor

  • deviation of pituitary stalk

Pituitary Apoplexy

• Cause:

  massive hemorrhage into pituitary adenoma (especially in patients on bromocriptine for pituitary adenoma) / dramatic necrosis / sudden infarction of pituitary gland

• 25% of patients with pituitary hemorrhage will present with apoplexy!

• Sheehan syndrome

  = postpartum infarction of anterior pituitary gland

• severe headache, nausea, vomiting

• hypertension

• stiff neck

• sudden visual-field defect, ophthalmoplegia

• obtundation (frequent)

• hypopituitarism (eg, secondary hypothyroidism)

• Area of destruction must be >70% to produce pituitary insufficiency!

• enlargement of pituitary gland

• NCCT:

  • increased density fluid level

• MR:

  • bright signal from presence of hemoglobin on T1WI with persistence over hyperintensity on T2WI

  • intermediate signal intensity from deoxyhemoglobin on T1WI + T2WI

Porencephaly

• = focal cavity as a result of localized brain destruction

  • AGENETIC PORENCEPHALY

    • = Schizencephaly (= true porencephaly)

  • ENCEPHALOCLASTIC PORENCEPHALY

    • Time of injury:	during first half of gestation
      Histo:	necrotic tissue completely reabsorbed without surrounding glial reaction (= liquefaction necrosis)

  • MR:

    • smooth-walled cavity filled with CSF on all pulse sequences (= porencephalic cyst)

    • lined by white matter

  • ENCEPHALOMALACIA

    • = Pseudoporencephaly = Acquired porencephaly

    • Cause:	infectious, vascular
      Time of injury:	after end of 2nd trimester (brain has developed capacity for glial response)
      Location:	parasagittal watershed areas with sparing of periventricular region + ventricular wall

  • CT:

    • hypodense regions

  • MR:

    • hypointense on T1WI + hyperintense on T2WI

    • surrounding hyperintense rim on T2WI = gliosis)

    • glial septa coursing through cavity identified on T1WI + proton density images

  • US:

    • septations in cavity well visualized

Primitive Neuroectodermal Tumor

• = PNET = PRIMARY CEREBRAL NEUROBLASTOMA

• = group of very undifferentiated tumors arising from germinal matrix cells of primitive neural tube

• Incidence:	<5% of supratentorial neoplasms in children, 30% of posterior fossa tumors
  Age:	mainly in children <5 years of age; M:F = 1:1
  Path:	most undifferentiated form of malignant small cell neoplasms grouped with Ewing sarcoma, Askin tumor
  Histo:	highly cellular tumors composed of >90 95% of undifferentiated cells (histologically similar to medulloblastoma, pineoblastoma, peripheral neuroblastoma)

• signs of increased intracranial pressure / seizures

• Location:

  • supratentorial: deep cerebral white matter (most commonly in frontal lobe), pineal gland, in thalamic + suprasellar territories (least frequently)

  • posterior fossa (= medulloblastoma)

  • outside CNS: chest wall, paraspinal region, kidney

• large (hemispheric) heterogeneous mass with tendency for necrosis (65%), cyst formation, calcifications (71%), hemorrhage (10%)

• thin rim of edema

• mild / moderate enhancement of solid tumor portion

• CT:

  • solid tumor portions hyperdense (due to high nuclear to cytoplasmic ratio)

• MR:

  • mildly hypointense on T1WI + hyperintense on T2WI

  • remarkably inhomogeneous due to cyst formation + necrosis

  • areas of signal dropout due to calcifications

  • hyperintense areas on T1WI + variable intensity (usually intermediate) on T2WI due to hemorrhage

  • inhomogeneously moderately enhancing mass with tumor nodules + ringlike areas surrounding central necrosis after Gd-DTPA

• Cx:

  meningeal + subarachnoid seeding (15 40%)

Progressive Multifocal Leukoencephalopathy

• = PML = rapidly progressive fatal demyelinating disease in patients with impaired immune system (chronic lymphocytic leukemia, lymphoma, Hodgkin disease, carcinomatosis, AIDS, tuberculosis, sarcoidosis, organ transplant)

• Etiology:	reactivation of ubiquitous JC papovavirus
  Pathophysiology:	destruction of oligodendrogliocytes leading to areas of demyelination + edema
  Histo:	intranuclear inclusion bodies within swollen oligodendrocytes (viral particles in nuclei), absence of significant perivenous inflammation

• progressive neurologic deficits, visual disturbances, dementia, ataxia, spasticity

• normal CSF fluid

• Location:	predilection for parieto-occipital region
  Site:	subcortical white matter spreading centrally into brainstem, deep gray matter

P.325




• bilateral white matter lesions (92%); confluent (94%); discrete (67%) in periventricular region + centrum semiovale + subcortical white matter

• gray matter lesions in thalamus + basal ganglia (from involvement of traversing white matter tracts)

• sparing of cortical gray matter

• mild cortical atrophy (up to 69%)

• ventricular dilatation (50%)

• NO contrast enhancement

• CT:

  • multicentric confluent white matter lesions of low attenuation with scalloped borders along cortex

  • NO mass effect, NO edema

• MR:

  • hypointense lesions on T1WI

  • patchy high-intensity lesions of white matter away from ependyma in asymmetric distribution on T2 + FLAIR

• Prognosis:	death usually within 6 months
  DDx in early stages:	primary CNS lymphoma

Rathke Cleft Cyst

• often asymptomatic

• hypopituitarism, visual disturbance, headache

• Location:

  commonly at junction of anterior + posterior pituitary gland; intra- / suprasellar in location

• may contain thickly mucinous material

• no contrast enhancement

• calcification rare

• MR:

  • thin-walled cyst

  • wall enhancement due to squamous metaplasia / displaced rim of pituitary tissue

  • simple / complex cyst contents fluid-fluid level

• DDx:

  craniopharyngeoma, macroadenoma

Reye Syndrome

• = hepatitis + encephalitis following viral upper respiratory tract infection with Hx of large doses of aspirin ingestion

• Age:

  in children + young adults

• obtundation rapidly progressing to coma

• initially (within 2 3 days) small ventricles

• later progressive enlargement of lateral ventricles + sulci

• markedly diminished attenuation of white matter

• Mortality:	15 85% (from white matter edema + demyelination)
  Dx:	liver biopsy

Reversible Posterior Leukoencephalopathy Syndrome

• = HYPERTENSIVE ENCEPHALOPATHY

• Emergency condition as patient may proceed to cerebral infarction and death if untreated!

• Cause:	acute rise in systemic blood pressure, preeclampsia or eclampsia, following immunosuppressive treatment with cyclosporine A, cisplatin, FK-501, tacrolimus
  Pathophysiology:	vasogenic edema due to loss of autoregulation (? due to decreased innervation of arteries by autonomic fibers)
  Location:	white matter of posterior half of brain

• hypodense white matter on NECT

• lesion hypointense on T1WI + hyperintense on T2WI

• lesion isointense on diffusion-weighted images (due to a net effect of elevated diffusion coefficient from vasogenic edema + T2 shine-through effect)

• no contrast enhancement

Sarcoidosis of CNS

• = inflammatory multisystem disease characterized by noncaseating granulomas

• Incidence:	CNS involvement in 1 5 8% (in up to 15% of autopsies)
  Age:	20 40 years (more common in women + people of West African descent); black:white = 10:1

• cranial neuropathy (facial > acoustic > optic > trigeminal nerves) secondary to granulomatous infiltration + leptomeningeal fibrosis (50 75%)

• peripheral neuropathy + myopathy

• aseptic meningitis (20%)

• diffuse encephalopathy, dementia

• pituitary + hypothalamic dysfunction (eg, diabetes insipidus in 5 10%)

• generalized / focal seizures (herald poorer prognosis)

• multiple sclerosislike symptoms (from multifocal parenchymal involvement)

• prompt improvement following therapy with steroids

• Location:	leptomeninges, dura mater, subarachnoid space, peripheral nerves, brain parenchyma, ventricular system
  	Affects meninges + cranial nerves more often than the brain!

• @ Meningeal / ependymal invasion

  • diffuse meningeal thickening + enhancement (most common) / meningeal nodules (less common)

    • Site:	particularly in basal cisterns (suprasellar, sellar, subfrontal regions) with extension to optic chiasm, hypothalamus, pituitary gland, cranial nerves where exiting brainstem
      Cx:	communicating / obstructive hydrocephalus is the most common finding (from arachnoiditis / adhesions)
      DDx:	carcinomatous / fungal / tuberculous meningitis

  • dense enhancement of falx + tentorium (granulomatous invasion of dura)

  • solitary / multiple dura-based mass

  • ependymal enhancement

• @ Parenchymal disease (due to extension from meningeal / ventricular surfaces)

  • isodense / hyperdense homogeneously enhancing small single / multiple nodules (invasion of brain parenchyma via perivascular spaces of Virchow-Robin)

  • Site:	periphery of parenchyma, intraspinal
    Cx:	stenosis / occlusion of blood vessels

• small vessel ischemic change

• lacunar infarction (especially brain stem + basal ganglia)

• focal / widespread infarcts of peripheral gray matter / at gray-white matter junction (periarteritis)

• reactive subcortical vasogenic edema

P.326

Schizencephaly

• = AGENETIC PORENCEPHALY = TRUE PORENCEPHALY

• = split brain

• = rare CNS malformation consisting of a full-thickness CSF-filled parenchymal cleft lined by gray matter extending from subarachnoid space to subependyma of lateral ventricles

• Frequency:	1:1,650
  Cause:	segmental developmental failure of cell migration to form cerebral cortex / vascular ischemia of portion of germinal matrix

• Time of injury:	30 60 days of gestation
  Often associated with:	polymicrogyria, microcephaly, gray matter heterotopia, septo-optic dysplasia

• Types:

  • Closed-lip schizencephaly = gray matter-lined lips in contact with each other (may be missed in imaging planes parallel to the plane of cleft)

    • walls appose one another obliterating CSF space

  • Open-lip schizencephaly = separated lips

    • CSF fills cleft from wall of lateral ventricle to pial surface

  • seizure disorder

  • mild / moderate developmental delay

  • range of normal mentation to severe mental retardation

  • blindness possible (optic nerve hypoplasia in 33%)

  • Location:

    most commonly near pre- and postcentral gyri (sylvian fissure); uni- / (mostly) bilateral; in middle cerebral artery distribution

  • cleft from wall of lateral ventricle to pial surface

    • full-thickness cleft through hemisphere with irregular margins

    • asymmetrical dilatation of lateral ventricles with midline shift

    • wide separation of lateral ventricles + squaring of frontal lobes

    • ventricle wall may be tented pointing to defect

  • cleft lined by gray matter (PATHOGNOMONIC)

  • absence of cavum septi pellucidi (66%)

  • absence / focal thinning of corpus callosum

  • polymicrogyria (66%) + heterotopias (common)

    • polymicrogyria / pachygyria adjacent to cleft

  • bilateral often symmetric intracranial cysts, usually around sylvian fissure

  • Prognosis:	severe intellectual impairment, spastic tetraplegia, blindness
    DDx:	(1) Pseudoporencephaly = acquired porencephaly = local parenchymal destruction secondary to vascular / infectious / traumatic insult (almost always unilateral)
    	(2) Arachnoid cyst
    	(3) Cystic tumor

Septo-Optic Dysplasia

• = DeMORSIER SYNDROME

• = rare anterior midline anomaly with

  • hypoplasia of optic nerves

  • hypoplasia / absence of septum pellucidum

    • Often considered a mild form of lobar holoprosencephaly

    • M:F = 1:3

    • Cause:	insult between 5 7th week of GA
      Associated with:	schizencephaly (50%)

    • hypothalamic hypopituitarism (66%):

      • diabetes insipidus (in 50%), growth retardation (deficient secretion of growth hormone + thyroid stimulating hormone)

    • diminished visual acuity (hypoplasia of optic discs), nystagmus, occasionally hypotelorism

    • seizures, hypotonia

    • small optic canals

    • hypoplasia of optic nerves + chiasm + infundibulum

    • dilatation of chiasmatic + suprasellar cisterns

    • fused dilated boxlike frontal horns squared off dorsally + pointing inferiorly

    • bulbous dilatation of anterior recess of 3rd ventricle

    • hypoplastic / absent septum pellucidum

    • thin corpus callosum

Sinus Pericranii

• = subperiosteal venous angiomas adherent to skull and connected by anomalous diploic veins to a sinus / cortical vein

• soft painless scalp mass that reduces under compression

• Location:

  frontal bone

• calvarial thinning + defect

• CT:

  • sessile sharply marginated homogeneous densely enhancing mass adjacent to outer table of skull, perforating it and connecting it with another similar structure beneath the inner table

• Angio:

  • extracalvarial sinus may not opacify secondary to slow flow

Spongiform Leukoencephalopathy

• rare, hereditary

• Age:

  >40 years

• deteriorating mental function

• confluent areas of diminished attenuation

Sturge-Weber-Dimitri Syndrome

• = ENCEPHALOTRIGEMINAL ANGIOMATOSIS

  • = meningofacial ANGIOMATOSIS

• = vascular malformation with capillary venous angiomas involving face, choroid of eye, leptomeninges

• Cause:

  persistence of transitory primordial sinusoidal plexus stage of vessel development; usually sporadic

• seizures (80%) in 1st year of life: usually focal involving the side of the body contralateral to nevus flammeus

• mental deficiency (>50%)

• increasing crossed hemiparesis (35 65%)

• hemiatrophy of body contralateral to facial nevus (secondary to hemiparesis)

• homonymous hemianopia

• @ FACIAL MANIFESTATION

  • congenital facial port-wine stain (nevus flammeus)

    • = telangiectasia of trigeminal region; usually 1st 2nd division of 5th nerve; usually unilateral

      • V₁ associated with occipital lobe angiomatosis

      • V₂ associated with parietal lobe angiomatosis

      • V₃ associated with frontal lobe angiomatosis

  P.327

  
  

  • @ CNS MANIFESTATION

    • leptomeningeal venous angiomas confined to pia mater

      • Location: parietal > occipital > frontal lobes

        • cortical hemiatrophy beneath meningeal angioma due to anoxia (steal)

        • tram track gyriform cortical calcifications >2 years of age; in layers 2-3 (-4-5) of opposing gyri underlying pial angiomatosis; bilateral in up to 20%

        • Location:

          temporo-parieto-occipital area, occasionally frontal, rare in posterior fossa

        • subjacent white matter hypodense on CT with slight prolongation of T1 + T2 relaxation times (gliosis)

        • choroid plexus enlargement ipsilateral to angiomatosis

        • ipsilateral thickening of skull + orbit (bone apposition as result of subdural hematoma secondary to brain atrophy)

        • elevation of sphenoid wing + petrous ridge

        • enlarged ipsilateral paranasal sinuses + mastoid air cells

        • thickened calvarium (= widening of diploic space)

        • Angio:

          • capillary blush

          • abnormally large veins in subependymal + periventricular regions

          • abnormal deep medullary veins draining into internal cerebral vein (= venous shunt)

          • failure to opacify superficial cortical veins in calcified region (markedly slow blood flow / thrombosis of dysgenetic superficial veins)

      • @ ORBITAL MANIFESTATION (30%)

        • ipsilateral to nevus flammeus:

        • congenital glaucoma (30%)

        • choroidal hemangioma (71%)

        • dilatation + tortuosity of conjunctival + episcleral + iris + retinal vessels

        • buphthalmos

        • Cx:

          retinal detachment

        • @ VISCERAL MANIFESTATION

          • localized / diffuse angiomatous malformation

          • Location:

            intestine, kidneys, spleen, ovaries, thyroid, pancreas, lungs

        • DDx:

          Klippel-Trenaunay syndrome, Wyburn-Mason syndrome

Subarachnoid Hemorrhage

• = blood between pia + arachnoid membrane

  Cause:

  • Spontaneous

    • Ruptured aneurysm (72%)

    • AV malformation (10%)

    • Hypertensive hemorrhage

    • Hemorrhage from tumor

    • Embolic hemorrhagic infarction

    • Blood dyscrasia, anticoagulation therapy

    • Eclampsia

    • Intracranial infection

    • Spinal vascular malformation

    • Cryptogenic in 6% (negative 4-vessel angiography; seldom recurrent)

  • Trauma (common)

    • concomitant to cerebral contusion

      • injury to leptomeningeal vessels at vertex

      • rupture of major intracerebral vessels (less common)

        • Location:

          • focal, overlying site of contusion / subdural hematoma

          • interhemispheric fissure, paralleling falx cerebri

          • spread diffusely throughout subarachnoid space (rare in trauma): convexity sulci > basal cisterns

  • Pathophysiology:

    irritation of meninges by blood + extra fluid volume increases intracranial pressure; may lead to vasospasm in 2 41%

  • acute severe headache ( worst in life ), vomiting

  • altered state of consciousness: drowsiness, sleepiness, stupor, restlessness, agitation, coma

  • spectrophotometric analysis of CSF obtained by lumbar puncture

• NECT (60 90% accuracy of detection depending on time of scan; sensitivity depends on amount of blood; accuracy high within 4 5 days of onset):

  • May occur in only two locations if subtle!

  • increased density in basal cisterns, superior cerebellar cistern, sylvian fissure, cortical sulci, intraventricular

  • along interhemispheric fissure = on lateral aspect irregular dentate pattern due to extension into paramedian sulci with rapid clearing after several days

  • cortical vein sign = visualization of cortical veins passing through extraaxial fluid collection

• MR (relatively insensitive within first 48 hours):

  • hyperintense sulci and cisterns on FLAIR (more sensitive than CT for small amounts of blood)

  • dirty CSF isointense to brain on T1WI + T2WI

  • low-signal intensity on brain surfaces in recurrent subarachnoid hemorrhages (hemosiderin deposition)

• Prognosis:

  clinical course depends on amount of subarachnoid blood

• Cx:

  • Acute obstructive hydrocephalus (in <1 week) secondary to intraventricular hemorrhage / ependymitis obstructing aqueduct of Sylvius or outlet of 4th ventricle

  • Delayed communicating hydrocephalus (after 1 week) secondary to fibroblastic proliferation in subarachnoid space and arachnoid villi interfering with CSF resorption

  • Cerebral vasospasm + infarction (develops after 72 hours, at maximum between 5 17 days, amount of blood is prognostic parameter)

  • Transtentorial herniation (cerebral hematoma, hydrocephalus, infarction, brain edema)

Subdural Hematoma of Brain

• = accumulation of blood in potential space between pia-arachnoid membrane (leptomeninges) + dura mater (= epiarachnoid space )

  Incidence:	in 5% of head trauma patients; in 15% of closed head injuries; in 65% of head injuries with prolonged interruption of consciousness
  Age:	accident-prone middle age; also in infants + elderly (large subarachnoid space with freedom to move in cerebral atrophy)
  Cause:	severe trauma, hemorrhagic diathesis

• Source of blood:

  • (1) pial cortical arteries + veins: direct trauma = penetrating injury

  P.328

  
  

  • (2) large contusions: direct / indirect trauma = pulped brain ; occasionally in blood clotting disorder / during anticoagulation therapy

  • (3) torn bridging cortical veins: indirect due to sudden de-/acceleration; also with forceful coughing / sneezing / vomiting in elderly

    • Elderly predisposed:

      due to longer bridging veins in senile brain atrophy

  • No consistent relationship to skull fractures!

• Pathogenesis:

  • differential movement of brain + adherent cortical veins with respect to skull + attached dural sinuses tears the bridging veins (= subdural veins), which connect cerebral cortex to dural sinuses and travel through the subarachnoid and subdural space

• Location:

  hematoma freely extending across suture lines, limited only by interhemispheric fissure and tentorium

• nonspecific headaches, nonlocalizing signs

• lethargy, confusion

• usually negative lumbar puncture

• low-voltage EEG

• CT:

  • hyperdense 65 90 HU (<1 week) / isodense 20 40 HU (1 2 weeks) / hypodense 0 22 HU (3 4 weeks)

    • False-negative CT scan:

      • high-convexity location, beam-hardening artifact, volume averaging with high density of calvarium obscuring flat en plaque hematoma, too narrow window setting, isodense hematoma due to delay in imaging 10 20 days post injury / due to low hemoglobin content of blood / lack of clotting, CSF-dilution from associated arachnoid tear

      • 38% of small subdural hematomas are missed!

      • Aids in detection of acute subdural hematoma:

        • thickening of ipsilateral portion of skull (hematoma of similar pixel brightness as bone)

        • subdural window setting = window level of 40 HU + window width of 400 HU

        • effacement of adjacent sulci

        • sulci not traceable to brain surface

        • ipsilateral ventricular compression / distortion

        • displacement of gray-white matter interface away from ipsilateral inner table

        • midline shift (often greater than width of subdural hematoma due to underlying brain contusion)

        • contrast enhancement of cortex but not of subdural hematoma

      • Aids in detection of bilateral subdural hematomas:

        • parentheses ventricles

        • ventricles too small for patient's age

          MR:

          see HEMATOMA OF BRAIN

• US (neonate):

  • linear / elliptical space between cranial vault + brain

  • flattened gyri + prominent sulci

  • distortion of ventricles, extension into interhemispheric space

• Limitations:

  • convexity hematoma may be obscured by pie-shaped display + loss of near-field resolution

    • Use contralateral transtemporal approach!

  • small loculations may be missed

• Prognosis:	poor (due to association with other lesions)
  DDx:	(1)	Arachnoid cyst (extension into sylvian fissure)
  	(2) Subarachnoid hemorrhage (extension into sulci)

Acute Subdural Hematoma

• Usually follows severe trauma, manifests within hours after injury

• Time frame:	<7 days old
  Associated with:	underlying brain injury (50%) with worse long-term prognosis than epidural hematoma, skull fracture (1%)

• Location:

  • over cerebral convexity, frequent extension into interhemispheric fissure, along tentorial margins, beneath temporal + occipital lobes; NO crossing of midline

  • bilateral in 15 25% of adults (common in elderly) and in 80 85% in infants

• extraaxial peripheral crescentic / convex fluid collection between skull and cerebral hemisphere usually with:

  • concave inner margin (hematoma minimally pressing into brain substance)

  • convex outer margin following normal contour of cranial vault

  • hyperdense collection of 65 100 HU, hypodense if hematocrit <29%

  • swirl sign = mixture of clotted and unclotted blood

  • occasionally with blood-fluid level

• after surgical evacuation: underlying parenchymal injury becomes more obvious

• after healing: ventricular + sulcal enlargement

• Cx:	Arteriovenous fistula (meningeal artery + vein caught in fracture line)
  Prognosis:	may progress to subacute + chronic stage / may disappear spontaneously
  Rx:	evacuation, but with poor response (due to high uncontrollable intracranial pressure from associated injuries)
  Mortality:	35 50% (higher number due to associated brain injury, mass effect, old age, bilateral lesions, rapid rate of hematoma accumulation, surgical evacuation >4 hours)

Interhemispheric Subdural Hematoma

• Most common acute finding in child abuse (whiplash forces on large head with weak neck muscles)

• predominance for posterior portion of interhemispheric fissure

• crescentic shape with flat medial border

• unilateral increased attenuation with extension along course of tentorium

• anterior extension to level of genu of corpus callosum

Subdural Hemorrhage in Newborn

• Cause:

  mechanical trauma during delivery (excessive vertical molding of head)

• 1. Posterior fossa hemorrhage

  • (a) tentorial laceration with rupture of vein of Galen / straight sinus / transverse sinus

  P.329

  
  

  • (b) occipital osteodiastasis = separation of squamous portion from exoccipital portion of occipital bone

  • high-density thickening of affected tentorial leaf extending down posterior to cerebellar hemisphere (better seen on coronal views)

  • mildly echogenic subtentorial collection

  • Cx:

    death from compression of brainstem, acute hydrocephalus

• 2. Supratentorial hemorrhage

  • laceration of falx near junction with tentorium with rupture of inferior sagittal sinus (less common than tentorial laceration)

    • hematoma over corpus callosum in inferior aspect of interhemispheric fissure

  • convexity hematoma from rupture of superficial cortical veins

    • usually unilateral subdural convexity hematoma accompanied by subarachnoid blood

    • underlying cerebral contusion

    • sonographic visualization of convexities difficult

Subacute Subdural Hematoma

• Time frame:

  7 22 days

• CT:

  • isodense hematoma of 25 45 HU (1 3 weeks), may be recognizable by mass effect:

    • effacement of cortical sulci

    • deviation of lateral ventricle

    • midline shift

    • white matter buckling

    • displacement of gray-white matter junction

  • contrast enhancement of inner membrane

• AID in Dx:

  contrast enhancement defines cortical-subdural interface

• MR (modality of choice in subacute stage):

  • high sensitivity for Met-Hb on T1WI (superior to CT during isodense phase for small subdural hematoma + for hematomas oriented in the CT scan plane, eg, tentorial subdural hematoma):

    • hyperintense on T1WI

Chronic Subdural Hematoma

• Time frame:	>22 days old
  Cause:	mild unremembered head trauma ?
  Pathogenesis:	vessel fragility accounts for repeated episodes of rebleeding (in 10 30%) following minor injuries that tear fragile capillary bed within neomembrane surrounding subdural hematoma

• Predisposing factors:

  • alcoholism, increased age, epilepsy, coagulopathy, prior placement of ventricular shunt

  • >75% occur in patients >50 years of age!

• Histo:

  hematoma enclosed by thick + vascular membrane, which forms after 3 6 weeks

• history of antecedent trauma often absent (25 48%)

• ill-defined neurologic signs + symptoms: cognitive deficit, behavioral abnormality, nonspecific headache

• progressive neurologic deficit

• low-voltage EEG, normal CSF

• often biconvex lenticular = medially concave configuration, esp. after compartmentalization secondary to formation of fibrous septa

• low-density lesion of 0 25 HU (= intermediate attenuation between CSF + brain):

  • different attenuations within compartments

  • sometimes as low as CSF

  • high-density components of collection (after common rebleeding)

  • fluid-sedimentation levels (sedimented fresh blood with proteinaceous fluid layered above)

• displacement / absence of sulci, displacement of ventricles + parenchyma

• No midline shift if bilateral (25%)

• absent cortical vein sign = cortical veins seen along periphery of fluid collection without passing through it (1 4 weeks after injury)

• DDx:

  Acute epidural hematoma (similar biconvex shape)

Subdural Hygroma

• = Traumatic subdural effusion

• = localized CSF-fluid collection within subdural space

• Cause:	(a) minor trauma results in separation of dura and arachnoid; proliferation of dural border cell layer results in neomembrane with hyperpermeable capillaries + efflux of serous fluid into subdural space
  	(b) traumatic tear in arachnoid with secondary ball valve mechanism
  Age:	most often in elderly + young children
  Time of onset:	6 30 days following trauma

• asymptomatic in majority

• decreased level of consciousness, confusion

• headaches, drowsiness

• radiolucent crescent-shaped collection (as in acute subdural hematoma) of CSF density

• no evidence of blood products (DDx to subdural hematoma)

• MR:

  • isointense to CSF / hyperintense to CSF on T1WI (increased protein content)

• Prognosis:	often spontaneous resorption; may develop into a chronic subdural hematoma
  DDx:	(1) Enlarged subarachnoid space
  	(2) Subdural empyema
  	(3) Chronic subdural hematoma
  	(4) Brain atrophy

Teratoma of CNS

• Incidence:	0.5% of primary intracranial neoplasms; 2% of intracranial tumors before age 15
  Histo:	mostly benign, occasionally containing primitive elements + highly malignant
  Location:	pineal + parapineal region > floor of 3rd ventricle > posterior fossa > spine (associated with spina bifida)

• heterogeneous midline lesion, occasionally homogeneous soft-tissue mass (DDx: astrocytoma)

• contains fat + calcium

• hydrocephalus (common)

P.330

Toxoplasmosis of Brain

• Organism:	obligate intracellular protozoan parasite Toxoplasma gondii, can live in any cell except for nonnucleated RBCs; felines are definite host (feces of house cat)
  Infection:	ingestion of undercooked meat (eg, pork, free-range chicken) containing cysts or sporulated oocysts / transplacental transmission of trophozoites; acquired through blood transfusion + organ transplantation; hematogenous spread

• Prevalence of seropositivity:

  • up to 20% of urban adults in United States;

  • up to 90% of European adults

• Histo:

  inflammatory solid / cystic granulomas as a result of glial mesenchymal reaction surrounded by edema + microinfarcts due to vasculitis

• Affected tissue:

  • @ Gray + white matter of brain

    • Most common cause of focal CNS infection mass effect in patients with AIDS!

  • @ Retina: most common retinal infection in AIDS

  • @ Alveolar lining cells (4%):

    • mimics Pneumocystis carinii pneumonia

  • @ Heart (rare):

    • cardiac tamponade / biventricular failure

  • @ Skeletal muscle

• asymptomatic

• lymphadenopathy

• malaise, fever

  • AIDS INFECTION = toxoplasmic encephalitis

    • = reactivation of a chronic latent infection in >95%

    • Incidence:	3 40% of AIDS patients
      Path:	well-localized indolent granulomatous process / diffuse necrotizing encephalitis

    • focal neurologic deficit of subacute onset (50 89%)

    • seizures (15 25%)

    • pseudotumor cerebri syndrome

  • Location:

    basal ganglia (75%), scattered throughout brain parenchyma at gray-white matter junction

  • multiple / solitary (up to 39%) lesions <2 cm with nodular / thin-walled (common) ring enhancement

  • surrounding white matter edema

  • double-dose delayed CT scans with higher detection rate for multiple lesions (64 72%)

  • hemorrhage and calcifications after therapy

  • MR:

    • restricted diffusion on DWI similar to an abscess

  • Dx:	improvement on therapy with pyrimethamine + sulfadiazine within 1 3 weeks / biopsy
    DDx:	CNS lymphoma (particularly with single lesion)
    	Multiple lesions suggest toxoplasmosis!

• INTRAUTERINE INFECTION

  • Time of fetal infection:	chances of transplacental transmission greater in late pregnancy
    Screening:	impractical due to high false-positive rate

  • Toxoplasma gondii found in ventricular fluid

  • chorioretinitis

  • mental retardation

  • thickened vault, sutures apposed / overlapping

  • hydrocephalus with return to normal / persistence of large head size

  • intracerebral calcifications in posterior aspect of brain

  • multiple irregular, nodular / cystlike / curvilinear calcifications in periventricular area + thalamus + basal ganglia + choroid plexus (= necrotic foci); bilateral; 1 20 mm in size; increasing in number + size (usually not developed at time of birth)

  • OB-US (as early as 20 weeks MA):

    • sonographic findings in only 36%

    • evolving symmetric ventriculomegaly

    • intracranial periventricular + hepatic densities

    • increased thickness of placenta

    • ascites

    • Microcephaly is NOT a feature of toxoplasmosis!

    • Dx:

      elevated toxospecific IgM levels in fetal blood

  • Dx:

    demonstration of elongated teardrop-shaped trophozoites in histologic sections of tissue

Tuberculosis

Cranial Tuberculous Meningitis

• Cause:	rupture of initial subependymal / subpial focus of tuberculosis (Rich focus) from earlier hematogenous dissemination into CSF space
  Predisposed:	in AIDS patients + infants + small children (part of generalized miliary tuberculosis / primary tuberculous infection)
  Location:	basal cisterns, interhemispheric fissure, sylvian fissure, sulci of cerebral convexities

• CT:

  • iso- / hyperattenuating meninges relative to basal cisterns

  • often homogeneous contrast enhancement extending into interhemispheric fissures + cortical surfaces

• MR:

  • normal at unenhanced SE (in early stage)

  • distention of affected subarachnoid spaces with mild shortening on T1 + T2 relaxation times compared with CSF

  • abnormal meningeal enhancement in basal cisterns (most pronounced) on gadolinium-enhanced T1WI (corresponds to gelatinous exudate)

  • abnormal enhancement of choroid plexus + ependymal lining (rare)

  • Cx:	(1) Communicating hydrocephalus (most common) / obstructive hydrocephalus (rare)
    	(2) Ischemic infarcts of basal ganglia + internal capsule (due to vascular compression / occlusive panarteritis in basal cisterns); MCA distribution most frequent
    DDx:	infection (nontuberculous bacteria, virus, fungus, parasite), inflammatory disease (rheumatoid disease, sarcoidosis), neoplasia (meningiomatosis, CSF-seeding neoplasm)

Spinal Tuberculous Meningitis

• MR:

  • cerebrospinal fluid loculi with cord compression

  • obliteration of spinal subarachnoid space:

    • loss of outline of spinal cord in cervicothoracic spine

    P.331

    
    

    • matting of nerve roots in lumbar region

  • nodular thick linear intradural enhancement of meninges

• Cx:

  syringomyelia, syringobulbia

Tuberculoma of Brain

• = result of granuloma formation within cerebral substance

• Incidence:	0.15% of intracranial masses in Western countries, 30% in underdeveloped countries
  Age:	infant, small child, young adult
  Associated with:	tuberculous meningitis in 50%

• history of previous extracranial TB (in 60%)

• Location:

  more common in posterior fossa (62%), cerebellar hemispheres (frontal + parietal lobes); may be associated with tuberculous meningitis

• solitary (70%) / multiple (30 60%) lesions; may be multiloculated

• NCCT:

  • isodense (72%) / hyperdense rounded / lobulated lesions of 0.5 4 cm in diameter with mass effect (93%)

  • moderate surrounding edema (72%) less marked than in pyogenic abscess

  • central calcification (29%)

• CECT:

  • homogeneous enhancement

  • ring blush (nearly all) with smooth / slightly shaggy margins + thick irregular wall around an isodense center (DDx: pyogenic abscess less thick + more regular)

  • target sign = central calcification in isodense lesion + ring-blush (DDx: giant aneurysm)

  • homogeneous blush in tuberculoma en plaque along dural plane (6%) (DDx: meningioma en plaque)

• MR:

  • noncaseating granuloma

    • hypointense relative to brain on T1WI

    • hyperintense on T2WI

    • homogeneous nodular enhancement

  • caseating granuloma

    • isointense to markedly hyperintense on T2WI

    • rim enhancement on T1WI

      • with a solid center

        • hypo- / isointense core on T1WI

        • iso- to hypointense core on T2WI

        • typically associated with surrounding edema

      • with necrotic center

        • hyperintense core on T2WI

  • DDx:

    other CNS infection (esp. toxoplasmosis, cysticercosis, fungus), lymphoma, atypical meningioma, radiation necrosis

Tuberous Sclerosis

• = TSC = BOURNEVILLE DISEASE = epiploia

• = inherited autosomal dominant neuroectodermal disorder characterized by multifocal systemic hamartomas + malformations that may affect CNS, kidney, lung, skin, heart with a spectrum of phenotypic expressions

• CLASSIC TRIAD (Vogt, 1908) in only 29% of patients:

  • (1) Facial angiofibroma

  • (2) Epileptic seizures

  • (3) Mental retardation

  • mnemonic:	zits, fits, nitwits
    Prevalence:	1:10,000 to 1:150,000 live births

  • family history of TSC in 25 50%

  • Cause:	autosomal dominant with low penetrance (frequent skips in generations); germ line mutation of tumor suppressor genes TSC1 on gene 9q34 and TSC2 on 16p13; sporadic mutations in 50 60 80%
    Dx:	A. Major features
    	(1) Cortical / subcortical tubers
    	(2) Subependymal giant cell astrocytoma
    	(3) Cardiac rhabdomyoma
    	(4) Facial angiofibroma
    	(5) Retinal hamartoma
    	(6) Renal angiomyolipoma
    	(7) Shagreen patches
    	(8) Ash-leaf spots
    	(9) Lymphangioleiomyomatosis
    	B. Minor features
    	(1) Gingival fibroma
    	(2) Dental pits
    	(3) Hamartomatous rectal polyps
    	(4) Renal cysts
    	(5) Cerebral white matter migration lines
    	(6) Confetti skin lesions
    	(7) Bone cysts
    	A diagnosis is definite with 2 major / 1 major + 2 minor features!

  • Prognosis:	30% dead by age 5; 75% dead by age 20
    Rx:	antiepileptic medication; ketogenic diet

  • @ CNS INVOLVEMENT (>95%)

    • myoclonic seizures (75 80%): often first + most common sign of tuberous sclerosis with onset at 1st 2nd year, decreasing in frequency with age

    • mental retardation (50 82%): mild to moderate (1/3) moderate to severe (2/3); progressive; observed in adulthood; common if onset of seizures before age 5 years

    • autism, behavioral + sleep + psychiatric disorders

    • 1. Subependymal hamartomas

      • Location:

        along ventricular surface of caudate nucleus, on lamina of sulcus thalamo-striatus immediately posterior to foramen of Monro (most often), along frontal + temporal horns or 3rd + 4th ventricle (less commonly)

      • multiple subependymal nodules of 1 12 mm:

        • candle drippings appearance

      • calcification with increasing age (in up to 88%)

      • MR:

        • subependymal nodules protruding into adjacent ventricle isointense with white matter

        • iso- to hyperintense on T1WI + hyper- and hypointense on T2WI relative to gray and white matter

        • minimal contrast enhancement (in up to 56%)

    • 2. Giant cell astrocytoma (in 15%)

      • = subependymal benign tumor with tendency for enlargement + growth into ventricle

      • Incidence:	5 15%; M:F = 1:1
        Location:	in the region of foramen of Monro

    • hypo- / isodense well-demarcated rounded mass:

      • 2 3 cm in diameter with interval growth

      P.332

      
      

      • partially calcified

      • uniform enhancement

      • frequent extension into frontal horn / body of lateral ventricle

    • hypo- / isointense on T1WI + hyperintense on T2WI

    • hydrocephalus (obstruction at foramen of Monro)

    • Cx:

      degeneration into higher grade astrocytoma

  • 3. Cortical / subcortical tubers (in 56%)

    • = CORTICAL / SUBCORTICAL HAMARTOMAS

    • Histo:	clusters of atypical glial cells surrounded by giant cells with frequent calcifications (if >2 years of age) = hamartomas
      Frequency:	multiple (75%); bilateral (30%)

    • large misshapen broadened gyri with central hypodense regions (due to abnormal myelination)

    • masslike / curvilinear calcification of cortical tubers (in 15% <1 year of age, in 50% by age 10)

    • MR:

      • relaxation time similar to white matter (if uncalcified)

      • multiple nodules hyperintense on T2WI / FLAIR + iso- to hypointense on T1WI (fibrillary gliosis / demyelination)

      • enhancement extremely rare

  • 4. Heterotopic gray matter islands in white matter

  • Histo:	grouping of bizarre and gigantic neuronal cells associated with gliosis + areas of demyelination
    Frequency:	in up to 93%
    Location:	along lines of neuronal migration

  • straight / curvilinear bands extending radially from ventricular wall

  • wedge-shaped lesion with apex at ventricular wall

  • conglomerate masses

  • calcification of all / part of nodule

  • may show contrast enhancement

  • CT:

    • hypodense well-defined regions within cerebral white matter

  • MR:

    • iso- to hypointense region on T1WI + well-defined hyperintense area on T2WI relative to normal white matter

• DDx of CNS lesions:

  • Intrauterine CMV / Toxoplasma infection (smaller lesions, brain atrophy, microcephaly)

  • Basal ganglia calcification in hypoparathyroidism / Fahr disease (location)

  • Sturge-Weber, calcified AVM (diffuse atrophy, not focal)

  • Heterotopic gray matter (along medial ventricular wall, isodense, associated with agenesis of corpus callosum, Chiari malformation)

  • Focal cortical dysplasia

  • Subependymal heterotopia

• @ SKIN INVOLVEMENT

  • Facial angiofibroma (former misnomer: adenoma sebaceum) in 80 90% = wartlike nodules of brownish red color averaging 4 mm in size with bimalar distribution ( butterfly rash )

  • Age:	first discovered at age 1 5 years; family history in 30%
    Path:	small hamartomas from neural elements with blood vessel hyperplasia = angiofibromas
    Location:	nasolabial folds, eventually covers nose + middle of cheeks

  • Shagreen rough skin patches (80%) = pigskin

    • = peau d'orange = patches of fibrous hyperplasia; in intertriginous + lumbar location

  • Ash leaf patches = hypopigmented macules shaped like ash / spearmint leaf on trunk + extremities (earliest manifestation in infancy); may be visible only under ultraviolet light

  • Ungual fibromas (15 50%):

    • sub- / periungual with erosion of distal tuft

  • Caf -au-lait spots

    • Incidence:	similar to that in general population
      DDx:	neurofibromatosis type 1, fibrous dysplasia

  • @ OCULAR INVOLVEMENT

    • Phakoma (>5%) = whitish disk-shaped retinal hamartoma = astrocytic proliferation in / near optic disc, often multiple + usually in both eyes

    • small calcifications in region of optic nerve head

    • optic nerve glioma

  • @ RENAL INVOLVEMENT

    • usually asymptomatic

    • flank pain, hematuria

    • renal failure in severe cases (5%); hypertension

      • 75% of patients die from complications of renal failure by age 20

    • 1. Angiomyolipoma (38 89%): usually multiple + bilateral; <1 cm in diameter

      • Cx:

        spontaneous retroperitoneal hemorrhage (subcapsular / perinephrc) with shock

    • 2. Multiple cysts of varying size in cortex + medulla mimicking adult polycystic kidney disease (15%)

      • Path:

        cysts lined by columnar epithelium with foci of hyperplasia projecting into cyst lumen

      • polycystic involvement in infants

    • 3. Renal cell carcinoma (1 3%), bilateral in 40%: usually during adulthood

      • Only 17 documented cases in literature by 1998

    • Recommendation:

      • US evaluation every 2 3 years before puberty + yearly thereafter to identify growing lesions

  • @ LUNG INVOLVEMENT (1 4%)

    • Age:

      3rd 5th decade; in women

    • progressive respiratory insufficiency

    • interstitial fibrosis in lower lung fields + miliary nodular pattern may progress to honeycomb lung (lymphangioleiomyomatosis = smooth muscle proliferation around blood vessels)

    • multiple bilateral small cysts in lung parenchyma on CT (26 39%)

    • repeated episodes of spontaneous pneumothorax (50%)

    • chylothorax

    • cor pulmonale

  • @ HEART INVOLVEMENT in children

    • Prevalence:

      decreases with increasing age (due to spontaneous tumor regression + better survival of patients without cardiac tumor)

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    • congenital cardiomyopathy

    • typically clinically silent

    • circumscribed / diffuse subendocardial rhabdomyoma (in 5 30%) of ventricle (70%) / atrium (30%)

    • aortic aneurysm

  • @ BONE INVOLVEMENT

    • sclerotic calvarial patches (45%) = bone islands involving diploe + internal table; frontal + parietal location

    • thickening of diploe (long-term phenytoin therapy)

    • bone islands in pelvic brim, vertebrae, long bones

    • expansion + sclerosis of rib (may be isolated)

    • periosteal thickening of long bones

    • bone cysts with undulating periosteal reaction in distal phalanges (most common), metacarpals, metatarsals (DDx: sarcoid, neurofibromatosis)

  • @ OTHER VISCERAL INVOLVEMENT

    • Adenomas + lipomyomas of liver

    • Adenomas of pancreas

    • Tumors of spleen

  • @ VASCULAR INVOLVEMENT (rare)

    • thoracic + abdominal arterial aneurysms

    • Path:

      vascular dysplasia with intimal + medial abnormalities of large muscular + musculoelastic arteries

Unilateral Megalencephaly

• = hamartomatous overgrowth of all / part of a cerebral hemisphere with neuronal migration defects

• intractable seizure disorder at early age, hemiplegia

• developmental delay

• moderately / marked enlargement of hemisphere

• ipsilateral ventriculomegaly proportionate to enlargement of affected hemisphere

• straightened frontal horn of ipsilateral ventricle pointing anterolaterally

• neuronal migration defects:

  • polymicrogyria

  • pachygyria

  • heterotopia of gray matter

  • white matter gliosis (low density in white matter on CT, prolonged T1 + T2 relaxation times on MR)

• Rx:

  partial / complete hemispheric resection

Vein of Galen Aneurysm

• = central AVM directly draining into secondarily enlarged vein of Galen (aneurysm is a misnomer)

• Anatomical types:

  • Type 1	= AV fistula fed by enlarged arterial branches leading to dilatation of vein Galen + straight sinus + torcular herophili
    Type 2	= angiomatous malformation involving basal ganglia + thalami midbrain draining into vein of Galen
    Type 3	= transitional AVM with both features

• Feeding vessels:

  • posterior cerebral artery, posterior choroidal artery (90%)

  • anterior cerebral artery + anterior choroidal artery

  • middle cerebral artery + lenticulostriate + thalamic perforating arteries (least common)

• Age at presentation:

  detectable in utero >30 weeks GA; M:F = 2:1

  • neonatal pattern (0 1 month)

    • high-output cardiac failure (36%) due to massive shunting

  • infantile pattern (1 12 months)

    • macrocrania from obstructive hydrocephalus

    • seizures

  • adult pattern (>1 year)

    • headaches intracranial hemorrhage

    • hydrocephalus

    • focal neurologic deficits (5%) due to steal of blood from surrounding structures

• cranial bruit

• May be associated with:

  porencephaly, nonimmune hydrops

• smoothly marginated midline mass posterior to indented 3rd ventricle

• prominent serpiginous network in basal ganglia, thalami, midbrain

• dilated straight + transverse sinus + torcular herophili

• dilatation of lateral + 3rd ventricle (37%)

• NCCT:

  • round well-circumscribed homogeneous slightly hyperdense mass in region of 3rd ventricular outlet

  • hyperdense intracerebral hematoma (ruptured AVM)

  • focal hypodense zones (ischemic changes)

  • rim calcification (14%)

• CECT:

  • marked homogeneous enhancement of serpentine structures + vein of Galen + straight sinus

• OB-US:

  • median tubular cystic space with high-velocity turbulent flow demonstrated by pulsed / color Doppler

  • brain infarction / leukomalacia (steal phenomenon with hypoperfusion)

  • cardiac enlargement (high-output heart failure)

  • dilated veins of head + neck

  • hydrocephalus (aqueductal obstruction / posthemorrhagic impairment of CSF absorption)

• MR:

  • areas of signal void

• Angio:

  • necessary to define vascular anatomy for surgical / endovascular intervention

• Cx:	subarachnoid hemorrhage
  Rx:	ligation, excision, embolization of vessels from transtorcular / transarterial approach
  Prognosis:	56% overall mortality; 91% neonatal mortality
  DDx:	pineal tumor, arachnoid / colloid / porencephalic cyst

Venous Angioma

• = Developmental venous anomaly

• = cluster of dilated medullary veins, which drain into an enlarged vein; bleed rarely

• Can be considered a normal variant!

• Histo:	venous channels without internal elastic lamina, separated by gliotic neural tissue that may calcify; probably representing persistent fetal venous system; normal intervening brain parenchyma
  Associated with:	increased incidence of cavernous angiomas which can bleed!

• soft + compressible without thrills / pulsations

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• distension with Valsalva maneuver

• commonly asymptomatic

• Location:

  deep cerebral / cerebellar white matter; most commonly adjacent to frontal horn

• no arterial vessels

• umbrella / spoked-wheel / medusa head configuration = multiple small radially oriented veins at periphery of lesion converging to a single larger vein

• Cx (uncommon):	hemorrhage, ischemia
  DDx:	Sturge-Weber disease (diffuse pial angiomatosis with venous-type capillaries)

Ventriculitis

• = EPENDYMITIS

• = inflammation of ependymal lining of one / more ventricles

• Cause:	(1) rupture of periventricular abscess (thinner capsule wall medially)
  	(2) retrograde spread of infection from basal cisterns

• CECT (necessary for diagnosis):

  • thin uniform enhancement of involved ependymal lining

  • often associated with intraventricular inflammatory exudate + septations

• Cx:	obstructive hydrocephalus (occlusion at foramen of Monro / aqueduct)
  DDx:	ependymal metastases, lymphoma, infiltrating glioma

Ventriculoperitoneal Shunt Malfunction

• Peritoneum is an efficient site of absorption

• Components:

  ventriculostomy catheter, pressure-sensitive valve + reservoir, barium-integrated silicone peritoneal catheter

• symptoms of increased intracranial pressure: seizures, headache, nausea, vomiting, lethargy, irritability

• abdominal pain, fever

• persistent bulging of anterior fontanel

• excessive rate of head growth

• slowed refill of shunt reservoir

Mechanical Shunt Failure

• Cause:

  occlusion of catheter by choroid plexus / glial tissue, disconnection of tubes

• sutural diastasis + increased size of cranial cavity

• increasing ventricular size:

  • interval increase since last exam

  • enlargement of temporal horns (earliest finding)

  • preferential enlargement of temporal horns in infants

  • N.B.:	(1) no enlargement with scarring of ventricular walls
    	(2) marked ventricular dilatation does not necessarily indicate shunt malfunction

• shuntogram (by scintigram / contrast radiography) determines site of obstruction

• brain edema tracking along shunt + within interstices of centrum semiovale (with partial obstruction)

• formation of white matter cyst surrounding ventricular catheter

Obstruction of VP Shunt

• Location:	ventricular end > peritoneal end
  Cause:	plugging of the catheter by brain parenchyma / choroid plexus /proteinaceous material / tumor cells; adhesions within peritoneum

• Tc-99m albumin colloid (injected into shunt tubing proximal to reservoir):

  • no uptake within ventricles + normal peritoneal activity (= proximal obstruction)

• Contrast study (injection of nonionic contrast material into shunt reservoir):

  • collection of contrast material at peritoneal end of shunt without spillage (= distal obstruction)

Disconnection & Breaks of VP Shunt

• Location:	connection of tubing to reservoir, at Y-connectors, areas of great mobility (neck)
  DDx:	pseudo-disconnection due to radiolucent tube components

Migration of VP Shunt

• PROXIMAL catheter: into soft tissues of neck / unusual locations within CNS

• Distal catheter: peritoneal cavity, thorax, abdominal wall, scrotum, perforation into GI tract

Leakage of VP Shunt

• = CSF escape without complete break / disconnection

• palpable cystic mass

• contrast verifies leak site

CSF Pseudocyst of VP Shunt

• shunt tubing coiled in an abdominal soft-tissue mass

• US / CT:

  • cyst surrounding catheter tip

• Cx:

  bowel obstruction

Infection of VP Shunt

Incidence:	1 5 38%
Time of onset:	within 2 months of shunt placement

• intermittent low-grade fever

• anemia, dehydration, hepatosplenomegaly

• stiff neck

• swelling + redness over shunting tract

• peritonitis

• ventriculitis (= enlarged ventricles with irregular enhancing ventricular wall septations)

• meningitis (= enhancement of cerebral cortical sulci)

Abdominal Complications of VP Shunt

• Ascites

• Pseudocyst formation

• Perforation of viscus / abdominal wall

• Intestinal obstruction

• Metastases to peritoneum: germinoma, medulloblastoma, astrocytoma, glioblastoma

Subdural Hematoma / Hygroma of VP Shunt

• Cause:	precipitous drainage of markedly enlarged ventricles
  Age:	usually seen in children >3 years of age with relatively fixed head size
  Prognosis:	small hematomas resolve on their own

Granulomatous Lesion of VP Shunt

• = rare granulomatous reaction adjacent to shunt tube within / near ventricle

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• irregular contrast-enhancing mass along course of shunt tube

Slit Ventricle Syndrome (0.9 3.3%)

• = proximal shunt failure from ventricular collapse

• Cause:	overdrainage of CSF, intermittent shunt obstruction, decreased intracranial compliance, periventricular fibrosis, intracranial hypotension
  Incidence:	0.9 3.3%

• intermittent / chronic headaches, vomiting, malaise

• slowed refill of shunt reservoir

• small / slitlike ventricles

Visceral Larva Migrans of Brain

• Organism:

  roundworm nematode (Toxocara canis)

• small calcific nodules, especially in basal ganglia + periventricular

• DDx: tuberous sclerosis

Von Hippel-Lindau Disease

• = vHL = RETINOCEREBELLAR ANGIOMATOSIS

• = inherited neurocutaneous dysplasia complex; autosomal dominant (gene located on chromosome 3p25-p26) with 80 100% penetrance + variable delayed expressivity; grouped under hereditary phakomatosis (although the skin is not affected); in 20% familial

• Prevalence:	1:35,000 1:50,000
  Age at onset:	2nd 3rd decade; M:F = 1:1

• Diagnostic criteria:

  • >1 hemangioblastoma of CNS

  • 1 hemangioblastoma + visceral manifestation

  • 1 manifestation + known family history

• Subclassification (NIH):

  • Type I	= renal + pancreatic cysts, high risk for renal cell carcinoma, NO pheochromocytoma
    Type IIA	= pheochromocytoma, pancreatic islet cell tumor (typically without cysts)
    Type IIB	= pheochromocytoma + renal + pancreatic disease

• @ CNS MANIFESTATION

  • Age at presentation: 25 35 years

  • signs of increased intracranial pressure: headache, vomiting

  • vision changes: reactive retinal inflammation with exudate + hemorrhage, retinal detachment, glaucoma, cataract, uveitis, decreasing visual acuity, eye pain

  • cerebellar symptoms: vertigo, dysdiadochokinesia, dysmetria, Romberg sign

  • spinal cord symptoms (uncommon): loss of sensation, impaired proprioception

  • 1. Retinal angiomatosis = von Hippel tumor (>50%) earliest manifestation of disease; multiple in up to 66%, bilateral in up to 50%

    • Histo:	hemangioblastoma of retina
      Dx:	indirect ophthalmoscopy + fluorescein angiography

    • small tumors rarely detected by imaging studies

    • globe distortion

    • thick calcified retinal density (calcified angioma-induced hematoma)

  • US:

    • small hyperechoic solid masses, most in temporal retina

  • Cx:	(1) repeated vitreous hemorrhage (frequent)
    	(2) exudative retinal detachment posteriorly

  • 2. Hemangioblastoma of CNS = Lindau tumor (40%)

    • = benign nonglial neoplasm as the most commonly recognized manifestation of vHL disease

      • Age:	15 40 years
        Site:	cerebellum (65%), brainstem (20%), spinal cord (15%); multiple lesions in 10 15% (may be metachronous)

      • 4 20% of single hemangioblastomas occur in von Hippel-Lindau disease!

      • CT:

        • large cystic lesion with 3 15-mm mural nodule (75%)

        • solid enhancing lesion (10%)

        • enhancing lesion with multiple cystic areas (15%)

        • intense tumor blush / blushing mural nodule

        • NO calcifications (DDx: cystic astrocytoma calcifies in 25%)

      • MR (modality of choice):

        • hypointense cystic component on T1WI (slightly hyperintense to CSF due to protein content); hyperintense on T2WI

        • small tubular areas of flow void within mural nodule (= enlarged feeding + draining vessels); intense contrast enhancement of mural nodule

        • slightly hypointense solid lesion on T1WI; hyperintense on T2WI; intense contrast enhancement

      • Angio:

        • intense staining of mural nodule ( mother-in-law phenomenon = tumor blush comes early, stays late, very dense)

        • presence of feeding vessels

      • Prognosis:

        most frequent cause of morbidity and mortality; frequent recurrence after incomplete resection

  • @ LABYRINTH

    • 1. Endolymphatic sac neoplasm

      • = aggressive adenomatous tumor with mixed histologic features

      • sensorineural hearing loss

      • Location:	retrolabyrinthine temporal bone
        Site:	endolymphatic sac

      • aggressive lytic lesion containing intratumoral osseous spicules + areas of hemorrhage

      • heterogeneous enhancement with hyperintense areas on T1WI + T2WI (due to hemorrhage)

  • @ HEART

    • Rhabdomyoma

  • @ KIDNEYS

    • polycythemia due to elevated erythropoietin level (in 15% with hemangioblastoma, in 10% with renal cell carcinoma)

      • Cortical renal cysts (75%)

        • multiple + bilateral (may be confused with adult polycystic kidney disease)

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      • Renal cell carcinoma (20 45%)

        • Age:

          20 50 years

        • multicentric in 87%, bilateral in 10 75%, may arise from cyst wall

        • sensitivity: 35% for angiography, 37% for US, 45% for CT (due to inability to reliably distinguish between cystic RCC, cancer within cyst, atypical cyst)

        • 50% metastatic at time of discovery

      • Prognosis:

        RCC is cause of death in 30 50% as the second most frequent cause of mortality!

      • Renal adenoma

      • Renal hemangioma

    • @ ADRENAL pheochromocytoma (in up to 10 17%), bilateral in up to 40%; confined to certain families

    • @ EPIDIDYMIS

      • Cystadenoma of epididymis

    • @ PANCREAS

      • Pancreatic cystadenoma / cystadenocarcinoma

      • Pancreatic islet cell tumor

      • Pancreatic hemangioblastoma

      • Pancreatic cysts (in 30 50%); incidence in autopsies up to 72%

        • usually multiple and multilocular cysts in pancreatic body + tail

        • Pancreatic cysts in a patient with a family history of von Hippel-Lindau disease are DIAGNOSTIC!

      • @ LIVER

        • Liver hemangioma

        • Adenoma

      • @ OTHERS

        • Paraganglioma

        • Cysts in virtually any organ: liver, spleen, adrenal, epididymis, omentum, mesentery, lung, bone

      • MULTIPLE ORGAN NEOPLASMS

        • @ Kidney	:	renal cell carcinoma (up to 40%), renal angioma (up to 45%)
          @ Liver	:	adenoma, angioma
          @ Pancreas	:	cystadenoma / adenocarcinoma
          @ Epididymis	:	adenoma
          @ Adrenal gland	:	pheochromocytoma

      • MULTIPLE ORGAN CYSTS

        • Kidney (usually multiple cortical cysts in 75 100% at early age, most common abdominal manifestation)

        • Pancreas (in 9 72% often numerous cysts; second most common affected abdominal organ)

        • Others: liver, spleen, omentum, mesentery, epididymis, adrenals, lung, bone