Internal auditory canal atresia and vestibulocochlear nerve hypoplasia
Presentation
Bilateral deafness. For cochlear implant.
Patient Data
Right internal auditory canal stenosis/atresia measuring 1.5mm along its max AP diameter on its midportion. Absent hypoplastic the cisternal and intracanailcular segments of the right vestibulocochlear nerves.
Enlarged dysplastic right vestibule with absent right lateral semicircular canal.
Relative narrowing of the left internal auditory canal measuring 2.4 mm along its max AP diameter on its midportion. ,Normal left 7th and 8th nerves.
Normal inner ear structures on the left side.
Right internal auditory canal stenosis/atresia measuring 1.5mm along its max AP diameter on its midportion. Absent hypoplastic the cisternal and intracanailcular segments of the right vestibulocochlear nerves.
Enlarged dysplastic right vestibule with absent right lateral semicircular canal.
Relative narrowing of the left internal auditory canal measuring 2.4 mm along its max AP diameter on its midportion. ,Normal left 7th and 8th nerves.
Normal inner ear structures on the left side.
Case Discussion
Internal auditory canal atresia is a rare entity. Hypoplasia of the vestibulocochlear nerves is a common association and an important consideration in the differential diagnosis of sensorineural hearing loss.
Internal auditory canal (IAC) stenosis is usually a unilateral temporal bone abnormality linked to congenital hearing loss. It frequently coexists with other inner ear abnormalities as well. Isolated congenital IAC stenosis without other inner ear anomalies has very rarely been reported.
Congenital internal auditory canal stenosis can be an important cause of sensorineural hearing loss, facial nerve palsy, and vestibular dysfunction.
Most IAC stenoses have normal facial nerve function, for it is assumed that the development
of the facial nerve is separate from that of the vestibulocochlear nerve. However, many cases with associated facial nerve palsy were reported. It was suggested that facial palsy might develop after inflammation, compression, or ischemia of the nerve within the stenosed IAC
Radiographically, IAC stenosis is diagnosed when the IAC diameter is < 2 mm in vertical diameter on MRI or CT.
IAC stenosis is an important consideration in the differential diagnosis of sensorineural hearing loss, as it is a relative contraindication for cochlear implant placement.
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