Internal auditory canal atresia with hypoplasia of the facial and vestibulocochlear nerves
Presentation
Right sensorineural hearing loss and facial palsy since birth.
Patient Data
Right internal auditory canal stenosis/atresia. Poor delineation/aplasia of the intracanailcular segments of the right facial and vestibulocochlear nerves.
Absent right lateral semicircular canal.
Normal left internal auditory canal, left 7th and 8th nerves and inner ear structures on the left side.
Case Discussion
Internal auditory canal atresia is a rare entity. Hypoplasia of the vestibulocochlear nerve 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 have been reported. It has been suggested that facial palsy might develop after inflammation, compression, or ischaemia 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 contraindication for cochlear implant placement secondary to nerve hypoplasia.
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