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Current Otolaryngology > XIV. Skull Base > Chapter 64. Osseous Dysplasias of the Temporal Bone >
| Osseous Dysplasias of the Temporal Bone: Introduction Patients with osseous dysplasias of the temporal bone, notably, fibrous dysplasia, Paget disease, osteopetroses, and osteogenesis imperfecta, present with hearing loss and external auditory canal obstruction that result in infection, lower cranial neuropathies, and temporal bone deformation. Differentiation among these entities is greatly helped by using coronal and axial high-resolution computed tomography (CT) imaging of the temporal bone and skull base. Outer, middle, and inner ear structures are detailed and foraminal stenoses are identified. Bone mineralization density appearance is the single most important imaging feature to secure a diagnosis. | | Fibrous Dysplasia Essentials of Diagnosis - External auditory canal stenosis.
- Progressive conductive hearing loss.
- Enlargement of the temporal bone.
- Abnormal skin pigmentation.
- Radiographic "ground glass" appearance.
General Considerations Fibrous dysplasia is perhaps the most common benign fibro-osseous disorder of the temporal bone. This poorly understood entity has three major classifications: (1) monostotic, (2) polyostotic, and (3) the McCune-Albright syndrome. The monostotic variant is the most common variety, accounting for approximately 70% of all cases, and is seen late in childhood. The disease may enter a dormant phase in puberty. Polyostotic disease manifests as multiple bony lesions and often has long bone involvement. The active phase of the disease extends into the third and fourth decades. McCune-Albright syndrome affects mostly females and is characterized by polyostotic fibrous dysplasia with endocrinopathy, cutaneous hyperpigmentation, and precocious puberty. Pathogenesis The radiographic appearance of fibrous dysplasia reflects the erosion of cortical bone by fibro-osseous tissue in the medullary cavity . Cortical bone is thinned by medullary fibrous tissue that is vascular , compressible , and weak. Histologically, there are interspersed regions of predominantly soft tissue or bone. Soft areas are abundant in collagen, and occasionally contain cysts. Areas of intermediate consistency are populated by fibroblasts. Clinical Findings Symptoms and Signs Common clinical manifestations of fibrous dysplasia of the temporal bone include external auditory canal stenosis, progressive hearing loss, and increased temporal bone size presenting as postauricular swelling. The dysplastic process may entrap skin within the external auditory canal, resulting in conductive hearing loss. Uncommonly, facial nerve paralysis may result from infected or erosive cholesteatoma. Imaging Studies The CT appearance of fibrous dysplasia may have several radiographic patterns: pagetoid, sclerotic, and cystic . Pagetoid is characterized by a mixture of dense and radiolucent areas of fibrosis with bone expansion. Sclerotic is homogeneously dense with bone expansion. Cystic has either spheric or ovale lucent regions with dense boundaries. Treatment & Prognosis The treatment for fibrous dysplasia is aimed at maintaining the patency of the external auditory canal and cranial nerve conduits . For ear canal stenosis, wide meatoplasty is performed to restore patency and exteriorize entrapped skin. Although sarcomatous degeneration is rare for those with fibrous dysplasia, the estimated incidences are 0.4% in monostotic and polyostotic disease, and 4% in McCune-Albright syndrome. Clinical features that suggest sarcomatous degeneration include pain, swelling, and radiographic evidence of bony destruction. The prognosis for malignant transformation is poor. | | Osteopetroses Essentials of Diagnosis - Conductive or sensorineural hearing loss.
- Cranial neuropathies.
- Facial dysfunction.
General Considerations The osteopetroses are a group of inheritable metabolic bone disorders. They result in diffuse, dense sclerosis and faulty bony remodeling. There are two forms: congenital and tarda. The congenital or lethal form is autosomal recessive, and manifests during infancy with pancytopenia secondary to obliteration of marrow spaces. Death due to hemorrhage, anemia, or overwhelming infection is common in infancy or childhood. The tarda or adult form is also known as Albers-Schƒnberg disease and is most commonly autosomal dominant. The adult form is benign and has a variable clinical course. Symptomatic patients present with problems that relate to bony overgrowth and foraminal stenosis. Hearing loss may be conductive or sensorineural owing to ossicular involvement or cochlear nerve impingement. Facial nerve function may be weak and spastic as a result of internal auditory canal narrowing. Other cranial nerve neuropathies may result from progressive stenosis of neural foramina. Pathogenesis The osteopetroses result from osteoclast dysfunction. Remodeled bone is faulty. Histologically, regions of endochondral ossification contain abnormal calcified cartilage. The osteopetrotic bone is immature, thick, dense, and brittle. This appearance gives rise to the names chalk or marble bone disease. Clinical Findings Symptoms and Signs In osteopetrosis congenita, findings that result from foraminal stenosis include optic atrophy, hearing loss, and facial palsy. Hearing loss tends to be conductive and is the result of ossicular infiltration by osteopetrotic bone and exostoses. In adult-type osteopetrosis, patients suffer multiple cranial nerve palsies involving cranial nerves I, II, III, V, and VII. Facial nerve paralysis can be recurrent and results from narrowing of the internal auditory, and labyrinthine and vertical fallopian canals. Conductive or mixed hearing loss is also due to ossicular chain involvement. Sensorineural hearing loss may arise from otic capsule and internal auditory canal infiltration by osteopetrotic bone. Imaging Studies Temporal bone CT findings in osteopetrosis congenita are notable for a small middle ear cavity with normal ossicles, obliteration of the mastoid antrum, and normal-appearing otic capsule. Temporal bone CT findings in osteopetrosis tarda are remarkable for a diffusely chalky, thickened cranial vault. Stenosis of neural foramina, encroachment of pneumatic spaces, infiltration of ossicles, and involvement of the otic capsule are other findings. Treatment & Prognosis There is no effective medical therapy for the osteopetroses, so limited surgical intervention may be indicated to decompress cranial canals and foramina. Of note, conductive hearing loss resulting from osteopetroses may be caused by either direct bony ossicular infiltration or epitympanic fixation. Treatment of conductive hearing loss by ossiculoplasty may be technically difficult because of dense middle ear bony disease and footplate abnormalities. Nonsurgical therapy with hearing aid rehabilitation should be considered before surgical intervention. It may be necessary to perform surgery to enlarge the external auditory canal to accommodate a hearing aid. Surgical decompression of the acoustic nerve for stabilization of sensorineural hearing loss is unproven. Facial nerve dysfunction generally presents with acute and recurrent episodes of facial palsy. Presurgical planning with a fine-resolution temporal bone CT scan can delineate stenotic sites for decompression. | | Paget Disease Essentials of Diagnosis - External auditory canal stenosis.
- Mixed hearing loss.
- Facial nerve dysfunction.
- Radiographic "cotton wool" appearing lesions.
General Considerations Paget disease, or osteitis deformans, is a disorder of excessive bone remodeling, primarily of the axial skeleton. Most cases are sporadic, but up to 15% are inherited in an autosomal pattern. The disease tends to occur after the fifth decade . The diagnosis is often made during evaluation for skeletal pain or incidentally on routine radiography. Pathogenesis The evidence for a possible viral etiology for Paget disease is based on findings of an immunoregulatory defect in chromosome 6 in association with viral inclusions in osteoclasts. The histologic pattern in Paget disease is one of alternating waves of osteoclastic and osteoblastic activity. Bone remodeling activity results in haphazard bony resorption followed by deposition of structurally weakened, demineralized cancellous bone. The early phase of the disease is dominated by bone resorption, which is seen as lytic lesions. The marrow space subsequently fills with fibrovascular tissue, which later undergoes sclerosis. Multifocal areas of lysis and sclerosis within the temporal bone and cranial base are seen. Temporal bone findings in Paget disease are notable for a tortuous external auditory canal, constriction of the middle ear cleft, bony changes of the ossicular chain, and demineralization of the otic capsule. Narrowing of the internal auditory canal can also cause acoustic-vestibular-facial dysfunction. Clinical Findings Symptoms and Signs Patients with Paget disease of the temporal bone present with tinnitus, vertigo, and hearing impairment . The pattern of hearing loss is mixed. The conductive component is most pronounced in the lower frequencies, whereas the sensorineural component most commonly involves the higher frequencies. Other cranial neuropathies due to foraminal stenosis are hemifacial spasm, trigeminal neuralgia, and optic atrophy. Imaging Studies Plain film x-rays of the skull may be diagnostic in Paget disease. The "cotton wool" appearance (coexistence of osteolysis and sclerosis) is almost pathopneumonic. The only other diagnostic consideration is the pagetoid variant of fibrous dysplasia. In approximately 10% of cases, Paget disease may present as a sharply delineated osteolytic skull lesion, osteoporosis circumscripta cranii. The CT appearance of the temporal bone reflects varying degrees of bone remodeling activity. There are two radiographic patterns: mosaic and translucent. In the mosaic pattern, diffuse areas of radiolucency adjacent to foci of irregular sclerosis are seen. In the translucent variant, the appearance is homogeneous, "washed out," and blurred. The otic capsule may lack its usual sharply demarcated boundary and may be accompanied by an overall diffuse demineralization of the petrous pyramid. The internal and external auditory canals and middle ear cleft may appear stenotic. Treatment Nonsurgical Measures Treatment of symptomatic Paget disease (bone pain, neuropathies, and cardiovascular stress) with calcitonin and bisphosphonates has been shown to induce biochemical and clinical improvement. Decremental levels of alkaline phosphatase and urinary hydroxyproline are seen in association with clinical improvement. Radiographic evaluation may document the arrest of bony lesions. Surgical Measures Surgical therapy for hearing loss and cranial neuropathy in Paget disease should be considered only as the last resort. Surgery for conductive hearing loss in Paget disease has not been satisfactory. Modern hearing devices are excellent alternatives to middle ear exploration and should be encouraged. Persistent symptomatic internal auditory canal stenosis with sensorineural hearing loss and facial nerve dysfunction following medical therapy may be an indication for surgical decompression. | | Osteogenesis Imperfecta Essentials of Diagnosis - Fragile bones.
- Blue sclera.
- Conductive and sensorineural hearing loss.
General Considerations Osteogenesis imperfecta carries the hallmark of fragile bones susceptible to easy fracture. Osteogenesis imperfecta has two major variants: congenita and tarda. The congenita variant is lethal. The newborn suffers from severe and life- threatening fractures sustained in utero and in the peripartum period. The tarda variant has a broad range of clinical outcomes that span the range from mild to lethal disease. Inheritance of the tarda variant is through either autosomal dominant or recessive transmission. The classic triad of blue sclera, multiple fractures, and early hearing loss is inherited through an autosomal dominant pattern of transmission. Pathogenesis The histopathology of osteogenesis imperfecta is marked by the deposition of osteopenic immature bony tissue that is weak and fragile. There is an increase in osteocytes in both woven and lamellar bone, and a relative reduction of matrix substance. The bone turnover rate is high. Conflicting theories have been proposed to explain the pathogenesis of this disease. Some advocate the hypothesis of osteoblast dysfunction that is responsible for immature bone deposition; others advocate the hypothesis of increased osteoclast activity. Still others implicate abnormal cell signaling due to defects of the extracellular matrix. Clinically, the regulatory defect in bone turnover results in pathologic fractures and hearing loss. Clinical Findings Symptoms and Signs Osteogenesis imperfecta tarda is a systemic disease and thus affects multiple organ systems, producing a broad array of clinical manifestations. Some of these conditions are dentinogenesis imperfecta, blue sclerae, loose joints, mitral valve prolapse, easy bruising, and growth deficiency. The hearing loss pattern may be conductive, sensorineural, or mixed. The onset of hearing loss is between the second and third decades. Hearing loss in osteogenesis imperfecta tarda can be audiometrically indistinguishable from otosclerosis. However, osteogenesis imperfecta has an earlier onset of hearing impairment and a higher incidence of sensorineural loss compared with otosclerosis. Footplate fixation in osteogenesis imperfecta tarda can arise either from an otospongiosis-like focus, as seen in early otosclerosis, or diffuse changes within the otic capsule. Several operative findings during stapedectomy differentiate osteogenesis imperfecta from otosclerosis. The canal wall skin is thin and fragile, and the scutum is brittle. Crural fractures are not uncommon, and there is excessive bleeding. The sensorineural component of the hearing loss in osteogenesis imperfecta is poorly understood but may involve microfractures of the otic capsule and encroachment of the bony labyrinth by dysplastic bone. Facial nerve dysfunction is a rare complication of osteogenesis imperfecta. Imaging Studies Temporal bone CT findings in osteogenesis imperfecta have substantial overlap with those found in otosclerosis. Both entities may have fenestral and retrofenestral findings. In fenestral disease, CT scanning shows an excrescent mass at the level of the promontory. In retrofenestral disease, the cochlea may be demineralized, with or without sclerosis. The "double ring" sign refers to the hypodense band that spirals along the cochlea. Extensive endochondral demineralization of the otic capsule is evident in severe cochlear otosclerosis. However, diffuse resorptive changes in vast areas of the otic capsule are more often seen in osteogenesis imperfecta. The findings of extensive facial nerve canal involvement and severe proliferative otic capsule dysplasia differentiate osteogenesis imperfecta tarda from cochlear otosclerosis. Treatment & Prognosis The primary otologic symptom in osteogenesis imperfecta is conductive hearing loss that occurs between the second and third decades. The benefit of medical therapy with calcitonin, sodium fluoride, and vitamin D is unclear. Surgical intervention with stapedectomy to improve conductive hearing loss in osteogenesis imperfecta tarda is technically more demanding than in otosclerosis. There is a greater tendency for bleeding and difficult footplate mobilization . Despite these challenges, stapes surgery in osteogenesis imperfecta has favorable short- and long- term results. Alternately, patients may choose to improve hearing with an amplification device. In the rare event of facial nerve dysfunction, CT imaging is useful to evaluate the fallopian canal. Sites obstructed by dysplastic bone can be delineated for surgical decompression. Aharinejad S, Grossschmidt K, Streicher J et al. Auditory ossicle abnormalities and hearing loss in the toothless mutation in the rat and their improvement after treatment with colony-stimulating factor 1. J Bone Miner Res. 1999;14:415. (Describes the effects of treating mutant rats with CSF-1 on hearing and temporal bone pathology.) [PMID: 10027906]
| Albright F, Butler MA, Hampton AO et al. Syndrome characterized by osteitis fibrosa disseminata, areas of pigmentation and endocrine dysfunction with precocious puberty in females. N Engl J Med. 1937;216:727. (Seminal article describing McCune Albright syndrome.)
| Bartynski WS, Barnes PD, Wallman JK. Cranial CT of autosomal-recessive osteopetrosis. Am J Neuroradiol. 1989;10:543. (Radiographic, clinical review of 8 patients with autosomal recessive osteopetrosis.) [PMID: 2501985]
| Benecke JE. Facial nerve dysfunction in osteopetrosis. Laryngoscope. 1993;103:494. (Review of the literature regarding facial nerve outcome in osteopetrosis.) [PMID: 8483364]
| Bergstrom LV. Osteogenesis imperfecta: otologic and maxillofacial aspects. Laryngoscope. 1977;87(Suppl 6):1. (Review article of patient clinical manifestations of osteogenesis imperfecta in the temporal bone and maxillofacial region.) [PMID: 330992]
| Bollerslev J, Grontved A, Andersen PE Jr. Autosomal dominant osteopetrosis: an otoneurologic investigation of the two radiological types. Laryngoscope. 1988;98:411. (Clinical findings correlated in a retrospective fashion with radiographic findings of 14 patients with autosomal dominant osteopetrosis.) [PMID: 3352441]
| Collins DH, Winn JM. Focal Paget's disease of the skull (osteoporosis circumscripta). J Pathol. 1955;69:1. (Seminal article describing the pathologic features of osteogenesis.)
| d'Archambeau O, Parizel PM, Koekelkoren E et al. CT diagnosis and differential diagnosis of otodystrophic lesions of the temporal bone. Europ J Radiol. 1990;11:22. (Retrospective review of 55 patients and their CT scans in order to assess the diagnostic and differential value of high-resolution CT scanning in the evaluation of temporal bone dysplasia.) [PMID: 2397727]
| Dort JC, Pollak A, Fisch U. The fallopian canal and facial nerve in sclerosteosis of the temporal bone: a histopathologic study. Am J Otol. 1990;11(5):320. (Study looking at detailed measures of the fallopian canal and facial nerve, correlating cross-sectional areas with facial nerve function.) [PMID: 2240173]
| Freeman DA. Southwestern internal medicine conference: Paget's disease of bone. Am J Med Sci. 1988;295(2):144. (Review of Paget disease.) [PMID: 3278610]
| Garretsen JTM, Cremers WRJ. Ear surgery in osteogenesis imperfecta. Arch Otolaryngol. 1990;116:317. (Presentation of pre- and postoperative hearing results after stapes surgery in osteogenesis imperfecta.) [PMID: 2306350]
| Hamersma H. Osteopetrosis (marble bone disease) of the temporal bone. Laryngoscope. 1970;80:1518. (Review article of osteopetrosis involving the temporal bone.) [PMID: 4991443]
| Khetarpal U, Schuknecht HF. In search of pathologic correlates for hearing loss and vertigo in Paget's disease: a clinical and histopathologic study of 26 temporal bones. Ann Otol Rhinol Laryngol. 1990;99(Suppl 145):1. (Histopathologic review of 26 patients to determine the etiology of conductive hearing loss.) [PMID: 2106820]
| Lustig LR, Holliday MJ, McCarthy EF, Nager GT. Fibrous dysplasia involving the skull base and temporal bone. Arch Otolaryngol. 2001;127:1239. (Retrospective review of the clinical presentation of 21 patients with histopathologically confirmed fibrous dysplasia.) [PMID: 11587606]
| McCune DJ, Bruch H. Osteodystrophia fibrosa: report of a case in which the condition was combined with precocious puberty, pathologic pigmentation of the skin, and hyperthyroidism, with review of the literature. Am J Dis Child. 1937;54:806. (Seminal article describing McCune Albright syndrome.)
| Milroy CM, Michaels L. Temporal bone pathology of adult-type osteopetrosis. Arch Otolaryngol. 1990;116:79. (Case presentation of the pathologic features in a patient with adult osteopetrosis.) [PMID: 2294946]
| Papadakis CE, Skoulakis CE, Prokopakis EP et al. Fibrous dysplasia of the temporal bone: report of a case and a review of its characteristics. Ear Nose Throat J. 2000;79:52. (Case presentation and review of clinical features of fibrous dysplasia.) [PMID: 10665192]
| Pedersen U. Osteogenesis imperfecta: clinical features, hearing loss and stapedectomy. Acta Oto-Laryngologica. 1985;Suppl 415:1. (Comparison of stapes surgery in osteogenesis imperfecta.) [PMID: 3859176]
| Reid IR, Miller P, Lyles K et al. Comparison of a single infusion of zoledronic acid with risedronate for Paget's disease. N Engl J Med. 2005;353:898. (Recent double-blinded clinical trial of single infusion versus 60 days of oral intake.) [PMID: 16135834]
| Sillence DO, Senn A, Danks DM. Genetic heterogeneity in osteogenesis imperfecta. J Med Genet. 1979;16:101. (Epidemiologic and genetic study of osteogenesis imperfecta in Australia.) [PMID: 458828]
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