Temporal bone osteogenesis imperfecta

Clinical History

A 34-year-old woman was being studied by ENT to investigate the cause of bilateral mixed hearing loss. She had a past medical history of multiple bone fractures in adolescence, and she had a hip replacement at the age of 32 years. On clinical examination she presents blue sclera.

Imaging Findings

Computed tomography images in bone algorithm reveal bilateral and symmetric, fenestral and retrofenestral lucencies. There is predominance for the pericochlear regions, with typical band-like lucency.

Discussion

Osteogenesis imperfecta (OI) type I is a genetic disorder of connective tissue, with autosomal dominant transmission (COL1A1 or COL1A2 mutation). OI is a rare disease and the type I is the most common and mildest form. [1]
Clinically type I OI is characterized by blue sclera, multiple bone fractures (less than 100), slightly short stature and occurrence of hearing loss in 50% of the cases. Usually, conductive hearing loss occurs in the second decade of life (from fractures of the bones of the middle ear) and progresses with a sensorineural component evolving into a mixed hearing loss. [1]
For the study of the temporal bone, CT is an excellent method of diagnosis showing bone abnormalities in detail. [2] The extent of temporal bone lucency in CT correlates with the degree of hearing loss. [2] Diagnostic key features that should be highlighted are bilateral and symmetric lucencies in the region of the fissula ante fenestram and also retrofenestral, predominantly in the pericochlear regions. [2, 3]
Magnetic resonance imaging in type I OI may also demonstrate demineralized pericochlear lesions with soft tissue signal intensity and contrast enhancement. [2, 3]
The main differential diagnosis are otospongiosis, Paget disease and otosyphilis. [1-3] Otospongiosis is a localized disease of the temporal bone, and the lucency areas are more frequently antefenestral. In Paget disease the demineralization pattern of temporal bone is more diffuse and asymmetric, and usually there are other associated skull abnormalities. Syphilis has a systemic involvement and serologic tests may disclose the diagnosis.
There is still controversy regarding the best treatment approach for hearing loss in osteogenesis imperfecta. Conductive hearing loss will benefit from surgical repair of the middle-ear bones. For sensorineural hearing loss hearing aids may be helpful, and cochlear implants may be used when hearing aids will no longer be useful. Some authors advocate stapedotomy showing successful results. [1, 4]

The diagnosis of osteogenesis imperfecta is usually suggested by family history, the combination of blue sclera, short stature and multiple fractures. Definitive diagnosis may be achieved with a genetic testing. [1] Patients should be surveilled for hearing loss starting from infancy, and clinical or surgical management will depend on the individual course of the disease. Temporal bone imaging abnormalities are characteristic with pericochlear band-like lucency, and bilateral and symmetric involvement. [1-4]

Differential Diagnosis List

Final Diagnosis

Temporal bone type I osteogenesis imperfecta

URL:	https://www.eurorad.org/case/11432
DOI:	10.1594/EURORAD/CASE.11432
ISSN:	1563-4086