3. Orbit

Authors: Dahnert, Wolfgang

Title: Radiology Review Manual, 6th Edition

Copyright 2007 Lippincott Williams & Wilkins

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Orbit

Differential Diagnosis of Orbital and Ocular Disorders

Ophthalmoplegia

• Lesions of

  • Oculomotor nerve (III)

    • innervates medial rectus, superior rectus, inferior rectus, inferior oblique muscle, pupilloconstrictor, levator palpebrae

  • Trochlear nerve (IV)

    • innervates superior oblique muscle

  • Abducens nerve (VI)

    • innervates lateral rectus muscle

Anopia

[numbers refer to drawing]

• MONOCULAR DEFECTS

  1

  = monocular blindness (optic nerve lesion in fracture of optic canal, amaurosis fugax)

• BILATERAL heteronymous DEFECTS

  2

  = bitemporal hemianopia (chiasmatic lesion)

• BILATERAL HOMONYMOUS DEFECTS

  3

  = homonymous hemianopia

  4

  = upper right-sided quadrantanopia

  3,4,5

  = most common type of hemianopia (CVA, brain tumor)

  

  Types of Anopia

Monocular Blindness In Adulthood

• Optic neuritis

• Vascular ischemia

  • Amaurosis fugax = cholesterol emboli from internal carotid artery occluding central retinal artery and its branches

  • Occult cerebrovascular malformation affecting the optic nerve

• Temporal arteritis

• Malignant optic glioma of adulthood

Orbit

Spectrum of Orbital Disorders

• INFLAMMATORY DISEASE

  • Tissue-specific inflammation:

    • orbital cellulitis, optic neuritis, scleritis, myositis, Graves disease

  • Panophthalmitis

  • Pseudotumor of orbit

• CYSTIC DISEASE

  • Dermoid cyst

  • Mucocele

  • Retro-ocular cyst (developmental)

P.338




• VASCULAR DISEASE

  • Cavernous angioma

  • Capillary angioma

  • Lymphangioma

  • Varix

  • Carotid-cavernous fistula

• TUMORS

  • Rhabdomyosarcoma

  • Optic nerve glioma

  • Meningioma

  • Lymphoma

  • Metastasis

Intraconal lesion

mnemonic:

Mel Met Rita Mending Hems On Poor Charlie's Grave

• Melanoma

• Metastasis

• Retinoblastoma

• Meningioma

• Hemangioma

• Optic glioma

• Pseudotumor

• Cellulitis

• Grave disease

Intraconal Lesion with Optic Nerve Involvement

• Optic nerve glioma

• Optic nerve sheath meningioma (10% of orbital neoplasm)

• Optic neuritis

• Inflammatory pseudotumor (may surround optic nerve)

• Sarcoidosis

• Intraorbital lymphoma (may surround optic nerve, older patient)

• Elevated intracranial pressure

  • = distension of optic sheath

  • bilateral tortuous enlarged optic nerve-sheath complex

Optic Nerve Tram-track Sign

• Optic nerve sheath meningioma

• Orbital pseudotumor

• Perioptic neuritis

• Perioptic hemorrhage

• Sarcoidosis

• Lymphoma / leukemia

• Metastasis

• Erdheim-Chester disease = systemic xanthogranulomatosis

Intraconal Lesion without Optic Nerve Involvement

• Cavernous hemangioma

• Orbital varix

• Carotid-cavernous fistula

• Arteriovenous malformation

  • least common of orbital vascular malformations (congenital, idiopathic, traumatic)

  • irregularly shaped intensely enhancing mass of enlarged vessels

  • associated with dilated superior / inferior ophthalmic vein

• Hematoma

• Lymphangioma

• Neurilemoma

  • commonly adjacent to superior orbital fissure, inferior to optic nerve

  • local bone erosion

Extraconal lesion

Extraconal-intraorbital Lesion

• BENIGN TUMOR

  • Dermoid cyst

  • Teratoma

    • <1% of all pediatric orbital tumors

    • areas of fat, cartilage, bone

    • expansion of bony orbit bone defect

  • Capillary hemangioma

  • Lymphangioma

  • Plexiform neurofibroma

  • Inflammatory orbital pseudotumor

  • Histiocytosis X

    • lesion usually arises from bone

• MALIGNANT TUMOR

  • Lymphoma / leukemia

  • Metastasis

  • Rhabdomyosarcoma

    mnemonic:

    MOLD

  • Metastasis

  • Others (rhabdomyosarcoma, lymphangioma, sinus lesion)

  • Lymphoma, Lacrimal gland tumor

  • Dermoid

Extraconal-extraorbital Lesion

• FROM SINUS

  • maxillary / sphenoid sinuses are rare locations of origin

  • Tumor:

    • squamous cell carcinoma (80%), lymphoma, adenocarcinoma, adenoid cystic carcinoma

  • Mucocele

  • Paranasal sinusitis:

    • Most common cause of orbital infection!

      Origin:	from ethmoid sinuses (in children), from frontal sinus (in adolescence)
      Organism:	Staphylococcus, Streptococcus, Pneumococcus

    • preseptal / orbital edema / cellulitis

    • subperiosteal / orbital abscess

    • mucormycosis (in diabetics) destroys bone + extends into cavernous sinus

    • Cx:

      • epidural abscess

      • subdural empyema

      • cavernous sinus thrombosis

      • meningitis

      • cerebritis

      • brain abscess

• FROM SKIN

  • Orbital cellulitis

• FROM LACRIMAL GLAND

  • mass arising from superolateral aspect of orbit

P.339

Orbital mass

Orbital Mass in Childhood

1. Dermoid cyst	46%
2. Inflammatory lesion	16%
3. Dermolipoma	7%
4. Capillary hemangioma	4%
5. Rhabdomyosarcoma	4%
6. Leukemia / lymphoma	2%
7. Optic nerve glioma	2%
8. Lymphangioma	2%
9. Cavernous hemangioma	1%

mnemonic:

LO VISHON

• Leukemia, Lymphoma

• Optic nerve glioma

• Vascular malformation: hemangioma, lymphangioma

• Inflammation

• Sarcoma: ie, rhabdomyosarcoma

• Histiocytosis

• Orbital pseudotumor, Osteoma

• Neuroblastoma

Primary Malignant Orbital Tumors

1. Retinoblastoma	86.0%
2. Rhabdomyosarcoma	8.1%
3. Uveal melanoma	2.3%
4. Sarcoma	1.7%

Secondary Malignant Orbital Tumors

1. Leukemia	36.7%
2. Sarcoma	14.3%
3. Hodgkin lymphoma	11.0%
4. Neuroblastoma	9.2%
5. Wilms tumor	6.7%
6. Non-Hodgkin lymphoma	5.6%
7. Histiocytosis	3.9%
8. Medulloblastoma	3.5%

Orbital Cystic Lesion

• Abscess

• Intraorbital hematoma

• Dermoid cyst

• Lacrimal cyst

• Lymphangioma

• Hydatid cyst

Orbital Vascular Tumors

• Orbital varix

• Arteriovenous malformation

• Carotid-cavernous fistula

• Hemangioma: capillary / cavernous

• Blood cyst

• Arterial malformation

• Glomus tumor

• Hemangiopericytoma

Mass in Superolateral Quadrant of Orbit

• Lacrimal gland tumor

• Dermoid cyst

• Metastasis (breast, prostate, lung)

• Lymphoma

• Leukemic infiltration of lacrimal gland

• Sarcoidosis

• Wegener granulomatosis

• Pseudotumor

• Frontal sinus mucocele

Extraocular Muscle Enlargement

• ENDOCRINE

  • Graves disease (50%)

  • Acromegaly

• INFLAMMATION

  • Myositis

    • rapid onset of proptosis, erythema of lids, conjunctival injection

      Location:

      single muscle (in adults); multiple muscles (in children)

    • enlarged extraocular muscle

    • positive response to steroids

  • Orbital cellulitis

  • Sj gren disease, Wegener granulomatosis, lethal midline granuloma, SLE

  • Sarcoidosis

  • Foreign-body reaction

• TUMOR

  • Pseudotumor

  • Rhabdomyosarcoma

  • Metastasis, lymphoma, leukemia

• VASCULAR

  • Spontaneous / traumatic hematoma

  • Arteriovenous malformation

  • Carotid-cavernous sinus fistula

Globe

Spectrum of Ocular Disorders

• CONGENITAL

  • Persistent hyperplastic primary vitreous

  • Coats disease

  • Coloboma

  • Congenital cataract

• VITREORETINAL

  • Vitreous hemorrhage

  • Retinal detachment

  • Choroidal detachment

  • Endophthalmitis

  • Retinoschisis

  • Retrolental fibroplasia

• TUMOR

  • Retinoblastoma

  • Choroidal hemangioma

  • Retinal angiomatosis

  • Melanocytoma

  • Choroidal osteoma

• TRAUMA

Microphthalmia

• = congenital underdevelopment / acquired diminution of globe

• BILATERAL with cataract

  • Congenital rubella

  P.340

  
  

  • Persistent hyperplastic vitreous

  • Retinopathy of prematurity

  • Retinal folds

  • Lowe syndrome

    • small globe + small orbit

• UNILATERAL

  • Trauma / surgery / radiation therapy

  • Inflammation with disorganization of eye (phthisis bulbi)

    • shrunken calcified globe + normal orbit

Macrophthalmia

• = enlargement of globe

• WITHOUT INTRAOCULAR MASS

  • generalized enlargement

    • Axial myopia (most common cause)

      • enlargement of globe in AP direction

      • thinning of sclera

    • Buphthalmos

    • Juvenile glaucoma

    • Connective tissue disorder:

      • Marfan syndrome, Ehlers-Danlos syndrome, Weill-Marchesani syndrome (congenital mesodermal dysmorphodystrophy), homocystinuria

      • wavy contour of sclera

  • focal enlargement

    • Staphyloma

    • Apparent enlargement due to contralateral microphthalmia

• WITH INTRAOCULAR MASS

  • (rare cause for enlargement)

  • with calcifications:

    • Retinoblastoma

  • without calcifications:

    • Melanoma

    • Metastasis

Ocular Lesion

Intraocular Calcifications

• Retinoblastoma (>50% of all cases)

• Astrocytic hamartoma

• Choroidal osteoma

• Optic drusen

• Scleral calcifications

  • in systemic hypercalcemic states (HPT, hypervitaminosis D, sarcoidosis, secondary to chronic renal disease)

  • in elderly: at insertion of extraocular muscles

• Retrolental fibroplasia

• Phthisis bulbi

  • secondary to trauma or infection

  • small contracted calcified disorganized nonfunctioning globe

    mnemonic:

    NMR CT

  • Neurofibromatosis

  • Melanoma (hyperdense melanin)

  • Retinoblastoma

  • Choroidal osteoma

  • Tuberous sclerosis

Noncalcified Ocular Process

• Uveal melanoma

• Metastasis

  • 86% of ocular lesions within globe; usually in vascular choroid

  • Origin: breast, lung, GI tract, GU tract, cutaneous melanoma, neuroblastoma

  • bilateral in 30%

• Choroidal hemangioma

• Vitreous lymphoma

  • diffuse ill-defined soft-tissue density

• Developmental anomalies

  • Primary glaucoma = enlargement of eye secondary to narrowing of Schlemm canal

  • Coloboma

  • Staphyloma

Vitreous Hemorrhage

Cause:

trauma, surgical intervention, arterial hypertension, retinal detachment, ocular tumor, Coats disease

• visual loss frequent

• US:

  • numerous irregular, poorly defined low-intensity echoes:

  • echogenic material moving freely within vitreous chamber during eye movement

  • voluminous hyperechoic fibrin clots not fixed to optic nerve (DDx to retinal detachment)

    Prognosis:	complete absorption / development of vitreous membranes (repetitive episodes)
    Cx:	retinal detachment (vitreous traction secondary to fibrovascular ingrowth following hemorrhage)

Dense Vitreous in Pediatric Age Group

• Retinoblastoma

• Persistent hyperplastic primary vitreous

• Coats disease

• Norrie disease

• Retrolental fibroplasia

• Sclerosing endophthalmitis

Leukokoria

• = abnormal white / pinkish / yellowish pupillary light reflex [leuko, Greek = white and koria, Greek = pupil]

• TUMOR

  • Retinoblastoma (most common cause 58%)

  • Retinal astrocytic hamartoma (3%):

    • associated with tuberous sclerosis + von Recklinghausen disease

  • Medulloepithelioma (rare)

• DEVELOPMENTAL

  • Persistent hyperplastic primary vitreous

    • (2nd most common cause 28%)

  • Coats disease (16%)

  • Retrolental fibroplasia (3 5%)

  • Coloboma of choroid / optic disc

• INFECTION

  • Uveitis

  • Larval granulomatosis (16%)

• DEGENERATIVE

  • Posterior cataract

P.341




• TRAUMA

  • Retinopathy of prematurity (5%)

  • Organized vitreous hemorrhage

  • Long-standing retinal detachment

Leukokoria in Normal-sized Eye

• CALCIFIED MASS

  • Retinoblastoma

  • Retinal astrocytoma

• NONCALCIFIED MASS

  • Toxocaral endophthalmitis

  • Coats disease

Leukokoria with Microphthalmia

• UNILATERAL

  • Persistent hyperplastic primary vitreous (PHPV)

• BILATERAL

  • Retinopathy of prematurity

  • Bilateral PHPV

Optic nerve

Optic Nerve Enlargement

• TUMOR:

  • Optic nerve glioma

  • Optic nerve sheath meningioma

  • Infiltration by leukemia / lymphoma

• FLUID:

  • Perineural hematoma

  • Papilledema of intracranial hypertension

  • Patulous subarachnoid space

• INFLAMMATION:

  • Optic neuritis

  • Sarcoidosis

• fusiform thickening

  • = lens-shaped thickening of nerve-sheath complex

  • with central lucency: meningioma

  • without central lucency: optic nerve glioma

• excrescentic thickening

  • = single / multiple nodules along nerve-sheath complex usually due to tumor

• tubular enlargement

  • = uniform enlargement of nerve-sheath complex

  • with central lucency: subarachnoid process (metastases, perineuritis, meningioma, perineural hemorrhage)

  • without central lucency: papilledema, leukemia, lymphoma, sarcoid, optic nerve glioma

Lacrimal gland

Lacrimal Gland Lesion

• INFLAMMATION

  • Dacryoadenitis

  • Mikulicz syndrome

    • = nonspecific enlargement of lacrimal + salivary glands

      Associated with:

      sarcoidosis, lymphoma, leukemia

  • Sj gren syndrome

    • = lymphocytic infiltration of lacrimal + salivary glands

    • decreased lacrimation, xerostomia

    • Often associated with:

      • rheumatoid arthritis, systemic lupus erythematosus, scleroderma, polymyositis

  • Sarcoidosis

• TUMOR

  (a) benign:	granuloma, cyst, benign mixed tumor (= pleomorphic adenoma)
  (b) malignant:	malignant mixed tumor (= pleomorphic adenocarcinoma), adenoid cystic carcinoma, lymphoma, metastasis (rare)

Lacrimal Gland Enlargement

mnemonic:

MELD

• Metastasis

• Epithelial tumor

• Lymphoid tumor

• Dermoid

Bilateral Lacrimal Gland Masses

mnemonic:

LACS

• Lymphoma

• And

• Collagen-vascular disease

• Sarcoidosis

P.342

Anatomy of Orbit

Orbital connections

Superior Orbital Fissure

Boundaries (Gray's Anatomy):

medial	:	sphenoid body
above	:	lesser wing of sphenoid = optic strut
below	:	greater wing of sphenoid
lateral	:	small segment of frontal bone

Contents:

• nerves:

  • III oculomotor n.

  • IV trochlear n.

  • V₁ ophthalmic branch of trigeminal n.:

    • lacrimal nerve

    • frontal nerve

  • VI abducens n.

  • sympathetic filaments of internal carotid plexus

• veins: superior + inferior ophthalmic vein

• arteries:

  • meningeal branch of lacrimal artery

  • orbital branch of middle meningeal artery

Inferior Orbital Fissure

Location: between floor + lateral wall of orbit; connects with pterygopalatine + infratemporal fossa

Contents:

• nerves: infraorbital + zygomatic nn. branches from pterygopalatine ganglion

• veins: connection between inferior orbital v. + pterygoid plexus

Optic Canal

completely formed by lesser wing of sphenoid

Contents:

• nerve: optic nerve (I)

• vessel: ophthalmic a.

Normal orbit measurements

Muscles

medial rectus muscle	4.1 0.5 mm
inferior rectus muscle	4.9 0.8 mm
superior rectus muscle	3.8 0.7 mm
lateral rectus muscle	2.9 0.6 mm
superior oblique muscle	2.4 0.4 mm

Superior ophthalmic vein

axial CT	1.8 0.5 mm
coronal CT	2.7 1.0 mm

Optic nerve sheath

retrobulbar	5.5 0.8 mm
waist	4.2 0.6 mm

Globe position

behind interzygomatic line 9.9 1.7 mm

Orbital compartments

the orbital septum + globe divide orbit into

• Anterior Compartment

  lids, lacrimal apparatus, anterior soft tissues

• Posterior Compartment

  • =Retrobulbar Space = the cone consisting of extraorbital muscles + envelope of fascia divides retrobulbar space into

  • intraconal space

  • extraconal space

  

  Coronal Orbital Tomogram through Midorbit

P.343

Orbital Spaces

globe:	subdivided into anterior + posterior segments by lens
optic nerve-
sheath complex:	optic nerve surrounded by meningeal sheath as extension from cerebral meninges
intraconal space:	orbital fat, ophthalmic a., superior ophthalmic v., nerves I, III, IV, V1, VI
conus:	incomplete fenestrated musculofascial system extending from bony orbit to anterior third of globe, consists of extraocular muscles + interconnecting fascia
extraconal space:	between muscle cone + bony orbit containing fat, lacrimal gland, lacrimal sac, portion of superior ophthalmic v.

Coronal Orbital Tomogram through Midorbit

P.344

Orbital and Ocular Disorders

Buphthalmos

• =hydrophthalmos = megophthalmos

• =diffuse enlargement of eye in children secondary to increased intraocular pressure

Cause:

• Congenital / infantile glaucoma

• Neurofibromatosis type 1: obstruction of canal of Schlemm by membranes / masses composed of aberrant mesodermal tissue

• Sturge-Weber-Dimitri syndrome

• Lowe (cerebrohepatorenal) syndrome

• Ocular mesodermal dysplasia (eg, Axenfeld or Rieger anomalies)

• Homocystinuria

• Aniridia

• Acquired glaucoma (rare)

Pathophysiology:

• obstruction of canal of Schlemm located between cornea + iris leads to decreased resorption of aqueous humor (= anterior chamber fluid) with scleral distension

• uniformly enlarged globe without mass of round / oval / bizarre shape

Rx: goniotomy (increases the angle of anterior chamber); trabeculotomy (lyses of adhesions)

Carotid-Cavernous Sinus Fistula

= abnormal communication between internal carotid artery + veins of cavernous sinus

Etiology:

• Trauma: laceration of ICA within cavernous sinus

  • usually secondary to basal skull fracture (cavernous ICA + small cavernous branches fixed to dura)

  • penetrating trauma

• Spontaneous: rupture of an intracavernous ICA aneurysm

Route of drainage:

• superior ophthalmic vein (common)

• contralateral cavernous sinus

• petrosal sinus

• cortical veins (rare)

• pulsating exophthalmos, chemosis, conjunctival edema

• persistent orbital bruit

• restricted extraocular movement

• decrease in vision due to increase in intraocular pressure (50%) = indication for emergent treatment

  • enlarged edematous extraocular muscles

  • dilatation of superior ophthalmic vein / facial veins / internal jugular vein

  • focal / diffuse enlargement of cavernous sinus

  • occasionally sellar erosion / enlargement

  • enlargement of superior orbital fissure (in chronic phase)

US + MR:

arterial flow in cavernous sinus + superior ophthalmic vein

Angio:

• ipsilateral ICA contrast injection shows wall of ICA to be incomplete

• contralateral ICA contrast injection + compression of involved ICA

• early opacification of veins of cavernous sinus

• retrograde flow through dilated superior ophthalmic v.

Rx: latex / silicone balloon detached inside cavernous sinus to plug laceration (ocular signs resolve within 7 10 days)

Choroidal Detachment

Cause: trauma, surgical intervention, spontaneous

US:

• two convex lines projecting into the eye from periphery of globe + advancing to ciliary body with posterior fixation outside the optic disk (= macula)

• minimal / no choroidal membrane mobility during eye movement

Choroidal Hemangioma

= vascular hamartoma

Age:	10 20 years (most common benign tumor in adults)
May be associated with:	Sturge-Weber syndrome
Location:	posterior pole temporal to optic disk (70%)

• 0.5 3-mm small tumor

• focal thickening of posterior wall of globe

• enhancement similar to choroid

• retinal detachment (frequent)

US:

• hyperechoic homogeneous mass

DDx: melanoma (choroidal excavitation)

Choroidal osteoma

= rare juxtapapillary tumor of mature bone

Age:	young woman
Location:	may be bilateral

small flat very dense curvilinear mass aligned with choroidal margin of globe

DDx: calcified choroidal angioma

Coats Disease

• = Retinal Telangiectasia = pseudoglioma

• = congenital idiopathic primary vascular malformation of the retina characterized by

  • multiple abnormal telangiectatic retinal vessels

  • lack of blood-retina barrier causing leakage of a lipoproteinaceous exudate into retina + subretinal space with secondary detachment of retina

Age: 6 8 years (but present at birth); M:F = 2:1

• strabismus

• may present with leukokoria (if retina massively detached) [16% of leukokoria cases]

• loss of vision, secondary glaucoma

• cholesterol crystals at funduscopy

Location:	unilateral in 90%
Associated with:	retinal detachment, slight microphthalmia

NO focal mass / calcification (HALLMARK)

US:

• clumpy particulate echoes in subretinal space (due to cholesterol crystals suspended in fluid)

• vitreous + subretinal hemorrhage (frequent)

P.345

DDx: unilateral noncalcifying retinoblastoma (before 3 years of age, no microphthalmia)

CT:

• unilateral dense vitreous in normal-sized globe

MR:

• hyperintense subretinal exudate on T1WI + T2WI (due to mixture of protein + lipid) / hypointense on T2WI (cholesterol crystals + membranous lipids)

• abnormal enhancement of retina at ora serrata + of detached retinal leaves

DDx:	Persistent hyperplastic primary vitreous (thick tubular retrolental mass) Retinopathy of prematurity
Rx:	photocoagulation / cryotherapy to obliterate telangiectasias (in early stages)

Coloboma

[koloboun, Greek = to mutilate]

= incomplete closure of embryonic choroidal fissure affecting eyelid / lens / iris / choroid / retina / macula; autosomal dominant trait with variable penetrance (30%) and expression; bilateral in 60%

Time of insult:	6th week of GA
May be associated with:	encephalocele, agenesis of corpus callosum
Location:	in 50% bilateral

• cystic outpouching (= herniation) of vitreous at site of optic nerve attachment

• small globe

DDx:

microphthalmos with cyst = duplication cyst, axial (high) myopia

Congenital Cataract

= opacification of lens

Etiology:	infection, hereditary
Location:	frequently bilateral

US:

• increase in thickness + echogenicity of posterior wall of lens intralenticular echoes

Dacryoadenitis

= infection of lacrimal gland

Organism:

staphylococci (most common), mumps, infectious mononucleosis, influenza

• homogeneous enlargement of lacrimal gland

• compression of globe

Dermoid Cyst of Orbit

Most common benign orbital tumor in childhood (45% of all masses)

Age:	1st decade
Histo:	contains keratin, hair, stratified epithelium + dermal appendages within thick capsule; usually arises in fetal cleavage planes (sutures)
Location:	in anterior extraconal orbit, upper temporal quadrant (60%), upper nasal quadrant (25%)

• well-defined cystic mass negative HU numbers

• thick surrounding capsule

• expansion / erosion of bony orbit

US:

encapsulated heterogeneous mass with variable cystic component

MR:

high signal intensity on T1WI + T2WI

Endophthalmitis

Infectious Endophthalmitis

Organism:	bacteria (rare in childhood, trauma, idiopathic), fungi, parasites
Cause:

• exogenous endophthalmitis: most commonly related to eye injury / surgery

• endogenous endophthalmitis: hematogenous spread from distant source of infection

US:

• medium- to high-intensity echoes dispersed throughout vitreous (DDx: echoes in vitreous hemorrhage are more mobile)

CT:

• increased attenuation of vitreous

• uveal-scleral thickening

• decreased attenuation of lens

Sclerosing Endophthalmitis

• = Toxocara Canis Endophthalmitis

• = granulomatous uveitis resulting in subretinal exudate, retinal detachment, organized vitreous

Age:	2 6 12 years
Mode of infection:
playing in soil contaminated by viable infective eggs from dog excrement (common in playgrounds)
Organism:	helminthic nematode Toxocara canis causing visceral / ocular larva migrans (0.5 mm long, 20 m wide); endemic throughout world; especially common in southeastern United States

Life cycle:

egg hatches into larva within intestines of definite host (dog) + develops into adult worm; alternatively dog may eat infective-stage larvae from intestines / viscera of other animals; in noncanine host larvae will not develop into adult worm, but burrow through intestinal wall and migrate to liver, lung, and other tissue including brain + eye

Pathophysiology:

migration through human tissue produces a severe eosinophilic reaction that becomes granulomatous; spreads hematogenously to temporal choroid

Path:

retina elevated + distorted + partially replaced by an inflammatory mass containing abundant dense scar tissue; subjacent choroid infiltrated with chronic inflammatory cells including eosinophils; proteinaceous subretinal exudate

• red hot eye, photophobia, pain

• anterior chamber flare cells, keratic precipitates

• vitreous synechia

• vitreitis = accumulation of cellular debris in vitreous

• leukokoria (16% of cases of childhood leukokoria)

• fever, hepatomegaly, pneumonitis, convulsions

P.346




• peripheral blood eosinophilia

Location:

usually unilateral

• eye of normal size without calcifications

• secondary retinal detachment

US:

• hypoechoic mass in peripheral fundus

• calcifications

CT:

• intravitreal mass

• focal uveoscleral thickening (granulomatous reaction around larva) with contrast enhancement

• increased density of vitreous cavity

MR:

• enhancing granuloma isointense to vitreous on T1WI

• mass usually hyperintense relative to vitreous on T2WI, occasionally hypointense (due to dense fibroconnective tissue)

Cx:	retinal detachment (due to subretinal fluid / vitreoretinal traction), cataract
Dx:	Enzyme-linked immunosorbent assay (ELISA) on blood serum / vitreous aspirate Histologic identification of organism
DDx:	retinoblastoma

Graves Disease of Orbit

• = Thyroid Ophthalmopathy = Endocrine Exophthalmos

• = increase in orbital pressure produces ischemia, edema, fibrosis of muscles

Etiology:	produced by long-acting thyroid-stimulating factor (LATS); probably immunologic cross-reactivity against antigens shared by thyroid + orbital tissue
Age:	adulthood; 5% younger than 15 years; M:F = 1:4
Histo:	deposition of hygroscopic mucopolysaccharides + glycoprotein (early) + collagen (late); infiltration by mast cells and lymphocytes, edema, muscle fiber necrosis, lipomatosis, fatty degeneration
Time of onset:	signs + symptoms usually develop within one year of the onset of hyperthyroidism

• proptosis

  • Most common cause of uni- / bilateral proptosis in adult!

• lid lag = upper eyelid retraction

• periorbital swelling

• conjunctival injection

• restricted ocular motility (correlates with increase in mean muscle diameters)

• progressive optic neuropathy (5%)

• hyperthyroidism; euthyroidism (in 10 15%); severity of orbital involvement unrelated to degree of thyroid dysfunction

Staging (Werner's modified classification):

Stage	I:	eyelid retraction without symptoms
Stage	II:	eyelid retraction with symptoms
Stage	III:	proptosis >22 mm without diplopia
Stage	IV:	proptosis >22 mm with diplopia
Stage	V:	corneal ulceration
Stage	VI:	loss of sight

Location:

bilateral in 70 85%; single muscle in 10%; asymmetrical involvement in 10 30%; all muscles equally affected with similar proportional enlargements; superior muscle group most commonly when only single muscle involved [former notion: inferior > medial > superior rectus muscle + levator palpebrae > lateral rectus muscle]

mnemonic:

I'M SLow

• Inferior

• Medial

• Superior

• Lateral

• proptosis = globe protrusion >21 mm anterior to interzygomatic line on axial scans at level of lens

• swelling of muscles maximally in midportion (relative sparing of tendinous insertion at globe) = Coke-bottle sign

• slight uveal-scleral thickening

• apical crowding = orbital apex involved late (pressure on optic nerve)

• dilatation of superior ophthalmic vein (compromised orbital venous drainage at orbital apex due to enlarged extraocular muscles)

• increase in diameter of retrobulbar optic nerve sheath (dural distension due to accumulation of CSF in subarachnoid space with optic neuropathy)

• increased density of orbital fat (late)

• anterior displacement of lacrimal gland

• intracranial fat herniation through superior ophthalmic fissure (best correlation with compressive neuropathy

MR:

• high signal intensity in enlarged eye muscles on T2WI (edema in acute inflammation)

Prognosis:	in 90% spontaneous resolution within 3 36 months; in 10% decrease in visual acuity (corneal ulceration / optic neuropathy)
Rx:	short- and long-term steroid therapy, cyclosporine, radiation, surgical decompression, correction of eyelid position
DDx:	pseudotumor (usually includes tendon of eye muscles)

Hemangioma of Orbit

• Most common benign orbital tumor

Location:

83 94% retrobulbar (intraconal)

• sharply demarcated oval mass in superior-temporal portion of conus (2/3) often sparing orbital apex

• displacement (not involvement) of optic nerve

• expansion of bony orbit

• uniform / inhomogeneous (when thrombosed) enhancement

• small calcifications (phleboliths)

• puddling of contrast material on angiography

US:

• well-defined encapsulated mass of intermediate echogenicity

• absent / poor predominantly venous flow

Capillary Hemangioma of Orbit

Incidence:	most common vascular tumor of orbit in children; 5 15% of all pediatric orbital masses
Age:	first 2 weeks of life; 95% in <6 months of age; M < F
Histo:	proliferation of endothelial cells with multiple capillaries

• proptosis, chemosis (= edema) of eyelid + conjunctiva exaggerated by crying

• associated with skin angioma (90%)

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Location:

anterior part of orbit, occasionally posterior

• mass with enhancement equal to / greater than orbital muscle

• poorly marginated (suggesting malignant cause)

• activity in radionuclide flow studies

US:

• poorly defined heterogeneous mass of intermediate echogenicity

• abundant internal flow decreasing with age

Prognosis:

often increase in size for 6 10 months followed by spontaneous involution within 1 2 years

Cavernous Hemangioma of Orbit

Frequency:	usually tumor of adulthood; 12 15% of all orbital masses; 1 2% of childhood orbital masses
Age:	20 40 years; F > M
Histo:	large dilated venous channels with flattened endothelial cells surrounded by fibrous pseudocapsule

• slowly progressive unilateral proptosis, diplopia, diminished visual acuity (optic nerve compression)

Infection of Orbit

Cause:	bacterial infection extending from paranasal sinuses (especially ethmoid + frontal sinuses), face, eyelid, nose, teeth, lacrimal sac through thin lamina papyracea + valveless facial veins into orbit
Organism:	staphylococci, streptococci, pneumococci

• lid edema, ocular pain, ophthalmoplegia

• fever, elevated WBC

Location:	preseptal = periorbital soft tissue; subperiosteal; peripheral = extraconal fat; extraocular muscles; central = intraconal fat; optic nerve complex; globe; lacrimal gland
Cx:	epidural abscess, subdural empyema, cavernous sinus thrombosis, cerebral abscess, osteomyelitis

Abscess of Orbit

Location:

most commonly in subperiosteal space on medial wall

• subperiosteal fluid collection

• displacement of thickened periosteal membrane + increased enhancement

• displacement of adjacent fat + extraocular muscles

MR:

• hyperintensity on T1WI + T2WI

Cellulitis of Orbit

=acute bacterial infection, often extending from paranasal sinuses / eyelids

• limitation of ocular movements

• fever

Location:

mostly confined to extraconal space

• proptosis

• scleral thickening

• enlargement + displacement of extraocular muscles (frequently medial rectus muscle)

• increased attenuation of retro-orbital fat + obliteration of fat planes

• opacification of ethmoid + maxillary sinuses (extension through thin lamina papyracea into orbit)

• subperiosteal abscess (with ethmoiditis)

MR:

• hypointense on T1WI + hyperintense on T2WI

• contrast-enhanced fat-suppressed images are most sensitive

US:

• diffuse hypoechoic area invading retrobulbar fat

Rx:	antibiotics + corticosteroids
Cx:	orbital abscess
DDx:	cannot be differentiated from edema, chloroma, leukemic infiltrate

Preseptal Cellulitis

• =fibrous orbital septum resists extension of infection into posterior compartment of orbit

• thickening of eyelids + septum

• swelling of anterior orbital tissues with increased density + obliteration of fat planes

Edema of Orbit

Location:

usually confined to preseptal structures (eyelid, face); involvement of orbital structures (rare)

• swelling of eyelids / face

• increased attenuation of orbital fat + obliteration of fat planes

• displacement + enlargement of extraocular muscles

MR:

• hyperintensity on T2WI

Lymphangioma of Orbit

Incidence:	3.5:100,000; 1 2% of orbital childhood masses; 8% of expanding orbital lesions
Histo:	dilated lymphatics, dysplastic venous vessels, smooth muscle, areas of hemorrhage
	(a) simple / capillary lymphangioma = lymphatic channels of capillary size
	(b) cavernous lymphangioma = dilated microscopic channels
	(c)cystic hygroma = macroscopic multilocular cystic mass
Age:	1st decade or later (mean age of 6 years)

• proptosis (sudden proptosis from spontaneous intratumoral hemorrhage = CARDINAL FEATURE; exacerbated during upper respiratory infections [rare])

• associated with lesions on lid, conjunctiva, cheek

• coincident lymphangiomatous cysts in oral mucosa

Location:

usually medial to optic nerve with intra- and extraconal component, crossing anatomic boundaries (conal fascia / orbital septum); may involve conjunctiva + lid

• poorly defined multilobulated inhomogeneous lesion

• single / multiple cystlike areas with rim enhancement (after hemorrhage) = blood cyst = chocolate cyst

• areas of enhancement (= venous channels) / ring enhancement (after hemorrhage)

• rarely contains phleboliths (DDx: hemangioma, orbital varix)

• mild to moderate enlargement of orbit

US:

P.348

• area of predominantly cystic heterogeneous texture with infiltrative borders

MR:

• may show hematoma of various duration within lesion

Prognosis:	no involution, progression slows with termination of body growth
DDx:	orbital varix

Lymphoma of Orbit

Usually presents without evidence of systemic disease; subsequent development of systemic disease frequent

Incidence:	3rd most common cause of proptosis after orbital pseudotumor + cavernous hemangioma; in 8% of leukemia; in 3 4% of lymphoma
Age:	50 years on average
Type:	usually non-Hodgkin B-cell lymphoma; Burkitt lymphoma with orbit as primary manifestation; Hodgkin disease rare

• painless swelling of eyelid

• exophthalmos (late in course of disease)

Location:	extraconal (especially lacrimal gland, anterior extraconal space, retrobulbar) > intraconal > optic nerve-sheath complex; may be bilateral    Lacrimal gland is a common site for leukemic infiltrates!
Growth types:

• well-defined high-density mass (most commonly about lacrimal gland)

• diffuse infiltration (tends to involve entire intraconal region)

• slight to moderate enhancement

US:

• solitary / multiple hypoechoic homogeneous masses with infiltrative borders

Metastasis to Orbit

Origin:	only in 50% known; carcinoma of breast + lung (adults); neuroblastoma > Ewing sarcoma, leukemia, Wilms tumor (children)
Location:	12% intraorbital, 86% intraocular especially in posterior temporal portion of uvea (vascular layer between retina + sclera) near macula; may be bilateral

CT:

• small areas of thickening + increased density

• subretinal fluid

Norrie Disease

• = Retinal Dysplasia

• = X-linked recessive disease: ? inherited form of persistent hyperplastic primary vitreous

• seizures, mental retardation (50%)

• hearing loss, deafness by age 4 (30%)

• bilateral leukokoria + microphthalmia

• cataract, blindness (absence of retinal ganglion cells)

  • microphthalmia

  • dense vitreous with blood-fluid level

  • cone-shaped central retinal detachment

  • calcifications

Ocular Trauma

Types:

• Simple / complicated contusion with rupture of ocular wall

• Simple / perforating injury to the globe

• Foreign body

• clinical evaluation: testing of visual acuity, slit-lamp evaluation of cornea + anterior segment, intraocular pressure measurement, funduscopy

US (used if ocular media opaque due to vitreous hemorrhage / hyphema / traumatic cataract)

• Hemorrhage

  • vitreous hemorrhage (53%)

    • visual loss frequent

    • echogenic material moving freely within vitreous chamber during eye movement

    Cx:	retinal detachment (vitreous traction secondary to fibrovascular ingrowth following hemorrhage)
    Rx:	vitrectomy

  • retrohyaloid hemorrhage (2%)

    • echogenic material remaining behind detached vitreous capsule during eye movement

  • hematoma in retro-ocular space

• Retinal detachment

  • total retinal detachment (18%)

    • slightly thick line of V shape with apex at optic disk

    • retina remains bound down at ora serrata

  • focal retinal detachment (2%)

    • elevated immobile line close to sclera at periphery of globe

• 3. Vitreous detachment (11%)

  • thin undulate mobile line moving away from posterior aspect of globe during eye motion

• 4. Choroidal detachment (5%)

• 5. Intraocular foreign body (7%)

  US sensitivity:	95% for intraocular + 50% for intraorbital foreign body
  Cx:	siderosis (if metallic); endophthalmitis

• 6. Lens dislocation (3%)

• 7. Thickening / rupture of ocular wall

• 8. Vascular complications

  • central renal artery occlusion

  • carotid-cavernous fistula

  • fistula of angular vein

Optic drusen

• = accretions of hyaline material on / near surface of optic disc; often familial

• headache, visual field defects

• pseudopapilledema

• small flat / round calcification at junction of retina + optic nerve bilateral in 75%

Optic pathway glioma

• = Juvenile pilocytic astrocytoma = optic nerve glioma

• = most common cause of optic nerve enlargement

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Incidence:	1% of all intracranial tumors; 2% of childhood orbital masses; 80% of primary tumors of optic nerve
Histo:	proliferation of well-differentiated astrocytes = low-grade glial neoplasm; most commonly pilocytic astrocytoma (in children) + glioblastoma (in adults)
Age:	1st decade (75%); peak age around 5 years; rare in adults without NF1 (GBM); M:F = 1:2
Associated with:	neurofibromatosis in 10 33 50% ( bilateral optic gliomas) 15 21% of NF1 patients have pilocytic astrocytoma of the optic pathway! Of all optic pathway gliomas 33% occur in NF1 patients!

• decreased visual acuity / visual-field defect

• axial proptosis with larger masses

• optic disk pallor, optic nerve atrophy (axonal damage)

• spasmus nutans (= high-frequency nystagmus of low amplitude associated with head nodding movement)

• precocious puberty (in 39% of only NF1 patients)

• tubular / fusiform / excrescentic well-circumscribed homogeneous enlargement of optic nerve-sheath complex:

  CHARACTERISTIC kinking / buckling of nerve

• posterior extension to involve chiasm + hypothalamus in 25 60% (indicates nonresectability)

• calcifications (rare)

• same attenuation as normal optic nerve; slight contrast enhancement

• ipsilateral optic canal enlargement (90%) >3 mm / 1 mm difference compared with contralateral side

US:

• well-defined homogeneous mass of medium echogenicity inseparable from optic nerve

MR:	more sensitive than CT in detecting intracanalicular + intracranial extent isointense to muscle on T1WI heterogeneously hyperintense on T2WI
DDx:	optic nerve sheath meningioma (no intracranial extension along optic pathway)

Malignant Optic Glioma of Adulthood

Incidence:	extremely rare; 30 cases in this century
Mean age:	6th decade; M:F = 1.3:1.0
Histo:	anaplastic astrocytoma / glioblastoma multiforme

• rapidly progressive monocular visual loss culminating in monocular blindness within a few weeks

• with retrograde tumor extension: contralateral temporal hemianopia, polyuria, polydipsia

• focal / diffuse enlargement of optic nerve

• hypo- to isointense on T1WI + hyperintense on T2WI

• obliteration of subarachnoid space around affected portion of nerve

• diffuse intense enhancement of optic nerve

• thickening + abnormal enhancement of optic nerve sheath

Tumor extension:	optic chiasm, hypothalamus, basal ganglia, brain stem, medial temporal lobes, leptomeninges, ependyma
Prognosis:	<1-year survival despite aggressive therapy
DDx:	(1) Optic neuritis (demyelinating plaques elsewhere) (2) Perioptic meningioma (hypointense on T2WI, stippled calcifications, hyperostosis) (3) Sarcoidosis, lymphoma, orbital pseudotumor (moderately / markedly hypointense on T2WI)

Optic Nerve Sheath Meningioma

= Perioptic Meningioma

Incidence:	10% of all intraorbital neoplasms; <2% of intracranial meningiomas
Age:	3rd 5th decade; M:F = 1:4;
	slightly more aggressive in children
Occasionally associated with:	neurofibromatosis type 2 (usually in teenagers)
Origin:	meningothelial cells in arachnoid rests of the meningeal investiture of optic nerve in orbit / middle cranial fossa

• insidious onset of progressive loss of visual acuity over months (optic atrophy), proptosis

• retinal examination:

  • papilledema

  • optociliary veins = dilated connections between ciliary circulation + central retinal vessels

• optic atrophy

Location:

• orbit = optic nerve sheath meningioma

• in optic canal = intracanalicular meningioma

• intracranial opening of optic canal = foraminal meningioma

• middle cranial fossa

• tubular (most commonly) / fusiform / excrescentic thickening of optic nerve

• calcifications in 20 50% (HIGHLY SUGGESTIVE)

• enlargement of optic canal

• sphenoid bone hyperostosis

US:

• hypoechoic tumor with irregular border

CECT: enhancement is the rule

• tumor enhancement around nonenhancing optic n.:

  • tram-track sign on axial view

  • ringlike / doughnut configuration on coronal view

  • linear high-attenuation area parallel to optic nerve (= tumor spread along subarachnoid space)

• minimal extension into optic canal (not uncommon)

MR:

• hypointense to fat on T1WI

• iso- to slightly hyperintense relative to optic nerve on T2WI

• tram-track sign = intensely enhancing extrinsic soft-tissue mass surrounding optic nerve on fat-suppressed T1WI

Optic Neuritis

= nerve involvement by inflammation, degeneration, demyelination

Etiology:

• Multiple sclerosis (involves optic nerve in 1/3)

• Inflammation secondary to ocular infection

• Degeneration (toxic, metabolic, nutritional)

• Ischemia

• Meningitis / encephalitis

  • 45 80% of patients develop multiple sclerosis within 15 years of their first episode of optic neuritis!

• ipsilateral orbital pain on eye movement

• sudden onset of unilateral loss of vision over several hours to several days

CT:

• normal / mildly enlarged optic nerve + chiasm

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• may show enhancement

MR:

• mild enlargement + enhancement of optic nerve well demonstrated on axial T1WI

Prognosis:

spontaneous improvement of visual acuity within 1 2 weeks

Perioptic Neuritis

Etiology:

demyelination from

• Multiple sclerosis

• Infection: measles, mumps, syphilis

• Sarcoidosis

• leptomeningeal enhancement obscures lucent optic nerve

Persistent Hyperplastic Primary Vitreous

= rare condition with persistence + proliferation of embryonic hyaloid vascular system of primary vitreous due to arrest of normal regression

May be associated with:

any severe ocular malformation / optic dysplasia / trisomy 13

Bilaterality is a feature of a congenital syndrome (Norrie disease, Warburg disease)!

• Primary vitreous

  • = fibrillar ectodermal meshwork + mesodermal tissue consisting of embryonic hyaloid vascular system; appears during 1st month of life; extends between lens + retina; involutes by 6th month of gestation

• Hyaloid artery

  • = important source of intraocular nutrition until 8th month of gestation; arises from dorsal ophthalmic artery at 3rd week of gestation; grows anteriorly with branches supplying vitreous + posterior aspect of lens

• Secondary / adult vitreous

  • begins to form during 3rd gestational month; a watery mass of loose collagen fibers + hyaluronic acid gradually replaces primary vitreous, which is reduced to a small S-shaped remnant (hyaloid canal = Cloquet canal) and serves as lymph channel

• unilateral leukokoria (2nd most common cause) [2 3% of leukokoria cases]

• seizures, mental deficiency, hearing loss

• cataract

• ophthalmoscopy: S-shaped tubular mass extending between posterior surface of lens + region of optic nerve head; lens opacity may preclude diagnosis

  • microphthalmia = small hypoplastic globe

  • retinal detachment (due to vitreoretinal traction in 30%)

US:

• hyperechoic band extending from posterior pole of globe to posterior surface of lens (= embryonic rest of primary vitreous)

• central anechoic line (= persistent hyaloid artery) visible in cases of echogenic vitreous hemorrhage

• hyperechoic band extending from papilla to ora serrata (= retinal detachment)

CT:

• enhancing cone-shaped central retrolental density extending from lens through vitreous body to back of orbit, just lateral to optic nerve

• small optic nerve

• deformity of globe + lens

• hyperdense vitreous (from previous hemorrhage)

• fluid-fluid levels from breakdown of recurrent hemorrhage in subhyaloid (between vitreous + retina) / subretinal space (between sensory + pigment epithelium)

• NO calcifications

MR:

• hyperintense vitreous body on T1WI + T2WI from chronic blood degradation products (methemoglobin) / proteinaceous fluid

• hypo- to isointense thin triangular band with base near optic disc and apex at posterior surface of lens

• marked enhancement of fibrovascular mass within vitreous

Cx:

• Glaucoma, cataract from recurrent spontaneous intravitreal hemorrhage (due to friable vessels)

• Proliferation of embryonic tissue

• Retinal detachment from organizing hemorrhage / traction

• Hydrops / atrophy of globe + resorption of lens

• Phthisis bulbi (scarred shrunken eye)

Pseudotumor of Orbit

• = Idiopathic Inflammatory Pseudotumor

• = nongranulomatous inflammatory process affecting all intraorbital soft tissues

Etiology:

• cause not apparent at time of study: bacterial, viral, foreign body

• systemic disease presently not apparent: sarcoidosis, collagen, endocrine

• idiopathic: probably abnormal immune response

Incidence:	25% of all cases of unilateral exophthalmos; most common cause of an intraorbital mass lesion in adult
Age:	young female
Histo:	lymphocytic infiltrate
May be associated with:	Wegener granulomatosis, sarcoidosis, fibrosing mediastinitis, retroperitoneal fibrosis, thyroiditis, cholangitis, vasculitis, lymphoma

• unilateral painful ophthalmoplegia

• proptosis, chemosis, lid injection

• impaired ocular movement

Location:

retrobulbar fat (76%), extraocular muscle (57%), optic nerve (38%), uveal-scleral area (33%), lacrimal gland (5%)

• tumefactive type (common)

  • discrete / poorly defined intra- / extraconal mass = pseudotumor close to surface margin of globe

• myositic type (unusual)

  • enlargement of one / more extraocular muscles close to insertion in globe with ill-defined margins

  • typically involves muscles + tendon insertions (DDx to Graves disease with muscle involvement only)

• inflammatory stranding of retrobulbar fat (may involve anterior compartment)

• uveoscleral thickening and enhancement (sclera near Tenon capsule)

• orbital muscle thickening

P.351




• enhancement of optic nerve sheath

• enlarged lacrimal gland

• proptosis

MR:

• lesion isointense to fat on T2WI

Prognosis:

• (1) remitting / chronic + progressive course

• (2) rapid dramatic + lasting response to steroid therapy

DDx:

• Lymphoma (may be confused with lymphoma clinically, radiographically, pathologically)

• Thyroid ophthalmopathy (tapering of distal muscles, painless proptosis)

• Radiation therapy

Retinal Astrocytoma

= low-grade neoplasm / hamartoma arising from the nerve fiber layer of retina / optic nerve, usually associated with tuberous sclerosis

Etiology:	tuberous sclerosis (53%); neurofibromatosis type 1 (14%); sporadic (33%)
Path:	usually multiple + bilateral in tuberous sclerosis; (1) small flat noncalcified semitranslucent lesion in posterior / peripheral retina (2) mulberry lesion = raised white tumor in posterior retina with fine nodularity containing calcifications + cystic fluid accumulations
Histo:	spindle-shaped fibrous astrocytes

• leukokoria (3% of all childhood cases of leukokoria)

• asymptomatic, progressive loss of vision

Location:	retina near optic disc retinal mass enhancement typically unilateral (DDx to drusen)
Cx: (1) Central retinal vein occlusion + secondary hemorrhage (2) Neovascular glaucoma (3) Extensive tumor necrosis

Retinal Detachment

Cause: trauma, tumor, exudative / inflammatory process, scar

US:

• curvilinear area of high echogenicity fixed at optic disk (= papilla) + extending to ora serrata

• V-shaped (with total detachment)

• in one quadrant only (partial detachment)

• thick folded retina with loss of mobility (long-standing detachment)

• subretinal space normal / occupied by blood, inflammation / tumor (depending on cause)

DDx: vitreous membranes, choroidal detachment (point of fixation not at papilla)

Retinoblastoma

= rare malignant congenital intraocular tumor arising from primitive photoreceptor cells of retina (included in primitive neuroectodermal tumor group)

Types:

• Nonheritable form (66%)

  • Sporadic postzygotic somatic mutation (subsequent generations unaffected)

    Mean age at presentation:

    23 months unilateral disease

  • Chromosomal anomaly

    • = monosomy 13 / deletions of 13q

    Associated with:

    microcephaly, ear changes, facial dysmorphism, mental retardation, finger + toe abnormalities, malformation of genitalia

• Heritable form

  • Heritable sporadic form (20 25%)

    • = sporadic germinal mutation (50% chance to occur in subsequent generations)

    Mean age at presentation:

    12 months
    bilateral retinoblastomas in 66%

  • Familial retinoblastoma (5 10%)

    • = autosomal dominant with abnormality of band 14 in chromosome 13 (95% penetrance)

    • Mean age at presentation: 8 months

    • usually 3 to 5 ocular tumors per eye

    • bilateral tumors in 66%

    • Risk of secondary nonocular malignancy:

    • osteo~, chondro~, fibrosarcoma, malignant fibrous histiocytoma (20% risk within 10 years, >90% by 30 years of age)

    • Trilateral retinoblastoma (rare variant)

      • = bilateral retinoblastomas + neuroectodermal pineal tumor (pineoblastoma)

    • Quadrilateral retinoblastoma

      • = trilateral retinoblastoma + 4th focus in suprasellar cistern

Incidence:	1:15,000 34,000 livebirths; most common intraocular neoplasm in childhood; 1% of all pediatric malignancies
Age:	mean age at presentation is 18 months; 98% in children <5 years of age; M:F = 1:1
Path:	(1) Exophytic form = proliferation into subretinal space with detachment of retina + invasion of vascular choroid (hematogenous spread) (2) Endophytic form = centripetal tumor invasion causing floating islands of tumor within semiliquid vitreous anterior chamber (3) Diffuse form = thin en-plaque lesion extending along retina

Histo:

• Flexner-Wintersteiner rosettes (in 50%)

  • = neuronal cells line up around an empty central zone filled with polysaccharides

    • Very specific for retinoblastomas!

• Homer-Wright rosettes

  • = neuronal cells line up around a central area containing a cobweb of filaments (also found in other primitive neuroectodermal tumors)

• fleurettes

  • = flowerlike groupings of tumor cells that form photoreceptor elements (specific for retinal differentiation)

• cat's eye = leukokoria (whitish mass behind lens) in 60%

  • About 50% of all childhood leukokoria are caused by retinoblastoma!

• decreased visual acuity, heterochromia iridis

• strabismus (crossed eyes), proptosis (less common)

• hyphema

• iris neovascularization, phthisis bulbi

P.352




• ocular pain from secondary angle-closure glaucoma

Location:

posterolateral wall of globe (most commonly); 60% unilateral; 40% bilateral + frequently synchronous (90% bilateral in inherited forms)

normal ocular size

US:

• heterogeneous hyperechoic solid intraocular mass

• cystic appearance upon tumor necrosis

• secondary retinal detachment in all cases

• acoustic shadowing (in 75%)

• vitreous hemorrhage frequent

CT:

• solid smoothly marginated lobulated retrolental hyperdense mass in endophytic type (rarer exophytic type grows subretinally causing retinal detachment)

• partial punctate / nodular calcification (50 75 95%)

  • Retinoblastoma is the most common cause of orbital calcifications!

• dense vitreous (common)

• extraocular extension (in 25%): optic nerve enlargement, abnormal soft tissue in orbit, intracranial extension

• contrast enhancement usual

• macrophthalmia

MR:

• iso- to mildly hyperintense tumor on T1WI relative to vitreous + moderate to marked enhancement

• distinctly hypointense on T2WI (similar to uveal melanoma)

• subretinal exudate usually hyperintense on T1WI + T2WI (proteinaceous fluid)

Cx:	(1) Metastases to: meninges (via subarachnoid space), bone marrow, lung, liver, lymph nodes (2) Radiation-induced sarcomas develop in 15 20%
Prognosis:	spontaneous regression in 1%; calcifications = favorable prognostic sign contrast enhancement = poor prognostic sign

Mortality:

• choroidal invasion: 65% if significant, 24% if slight

• optic nerve invasion:

  • <10% if not invaded

  • 15% if through lamina cribrosa

  • 44% if significantly posterior to lamina cribrosa

• margin of resection not free of tumor: >65%

DDx:

• Retinoma = retinocytoma (benign variant)

• Toxocara canis infection (no calcification)

• Retrolental fibroplasia (microphthalmia)

• Coats disease (subretinal exudation, no calcification)

• Norrie disease (retinal dysplasia)

• Persistent hyperplastic primary vitreous (hypoplastic globe, no calcification)

Retrolental Fibroplasia

• = Retinopathy of Prematurity

• = bilateral often asymmetric postnatal fibrovascular organization of vitreous humor, which usually leads to retinal detachment

Pathophysiology:

• retinal vascularization occurs in 4th 9th months of fetal life progressing from the papilla to the periphery; vascularization is incomplete in premature neonates especially in temporal sectors

Predisposed: premature infants with respiratory distress syndrome requiring prolonged oxygen therapy

Severity directly related to:

• degree of prematurity

• birth weight

• amount of oxygen used in therapy

• leukokoria in severe cases (traction retinal detachment, usually bilateral + temporal) [3 5% of all childhood leukokoria cases]

• Ophthalmoscopic stages:

  1st stage	=	arteriolar narrowing of most immature vessels at the border of the vascular-avascular retina (from spasm as a reaction to hyperoxygenation)
  2nd stage	=	dilatation + elongation + tortuosity of retinal vessels (after oxygen withdrawal)
  3rd stage	=	retinal neovascularization with growth into vitreous leads to vitreous hemorrhage
  4th stage	=	fibrosis with retraction of fibrovascular tissue + retinal detachment

  bilateral microphthalmia retinal detachment

US:

• hyperechoic tracts extending from temporal side of periphery of retina to vitreous behind the lens

CT:

• dense vitreous bilaterally (neovascular ingrowth)

• dystrophic calcifications in choroid + lens (late stage)

MR:

• hyperintense vitreous on T1WI + T2WI (from chronic subretinal hemorrhage)

• hypointense retrolental mass (apposition of detached leaves of retina displaced from retinal pigment layer)

Prognosis:

• spontaneous regression of vitreous neovascularization (85 95%) retinal detachment

• progression to cicatricial stage characterized by formation of dense membrane of gray-white vascularized tissue in retrolental vitreous + retinal detachment + microphthalmia

DDx: Retinoblastoma (calcifications in eye of normal size)

Rhabdomyosarcoma

Most common primary malignant orbital tumor in childhood

• 10% occur primarily in orbit

• 10% metastasize to / invade orbit

Incidence:	3 4% of all pediatric orbital masses
Histo:	arising from undifferentiated mesenchyma of orbital soft tissues (not from striated muscle) (1) embryonal type (75%) (2) alveolar type (15%) (3) pleomorphic type (10%)
Age at presentation:	average 7 years; 90% by 16 years of age; M > F
Rarely associated with:	neurofibromatosis

• rapidly progressive exophthalmos + proptosis of upper lid

Location:

superior orbit / retrobulbar (71%), lid (22%), conjunctiva (7%)

• large soft-tissue density mass with ill-defined margins (extraocular muscles not involved)

• extension into preseptal space, adjacent sinus, nasal cavity, intracranial cavity with bony erosion

P.353




• may show significant enhancement

US:

• heterogeneous well-defined irregular mass of low to medium echogenicity

Metastases:	lung, bone marrow, cervical lymph nodes (rare)
Prognosis:	(1) 40% survival after exenteration (2) 80 90% survival after radiation therapy (4,000 5,000 rad) + chemotherapy (vincristine, cyclophosphamide, doxorubicin)
DDx:	pseudotumor, lymphoma

Staphyloma

= sacculation of posterior pole of globe (or berrylike protrusion of cornea)

Prevalence:	increasing with size of globe
Cause:	axial myopia (temporal side of optic disc / anteriorly / along equator), trauma, scleritis, necrotizing infection
focal bulge + thinning of sclera
Cx:	advanced chorioretinal degeneration (77%), choroid retraction from optic disc, posterior vitreous detachment, choroidal hemorrhage, retinal detachment, cataract, glaucoma

Uveal Melanoma

Most common primary intraocular neoplasm in adult Caucasian

Age:	50 70 years
Location:	choroid (85 93%) > ciliary body (4 9%) > iris (3 6%); almost always unilateral

• retinal detachment, vitreous hemorrhage

• astigmatism, glaucoma

US:

• small flat hyperechoic solid mass

CT:

• ill-defined hyperdense thickening of wall of globe with inward bulge

MR:

• sharply circumscribed hyperintense lesion on T1WI (paramagnetic properties of melanin)

Metastases to:

globe, optic nerve; liver, lung, subcutis

Varix of Orbit

Etiology:

• Congenital: venous malformation / venous wall weakness

• Acquired: intraorbital / intracranial AVM

• intermittent exophthalmos associated with straining

• frequent blindness

• involvement of superior / inferior orbital vein; phleboliths rare

• may produce bony erosion without sclerotic reaction

• enlargement of mass during Valsalva maneuver / jugular vein compression

• well-defined markedly enhancing mass

• spontaneous thrombosis (common)

US:

• anechoic tubular / oval structure thrombus

• venous flow increasing with Valsalva

MR:

• flow void (rapid flow) / flow-related enhancement (slow flow)

Warburg Disease

= autosomal recessive syndrome characterized by

• bilateral persistent hyperplastic primary vitreous

• hydrocephalus, lissencephaly

• mental retardation

• bilateral leukokoria + microphthalmia