Presentation
Bilateral sensorineural hearing loss. Preoperative for cochlear implantation.
Patient Data
Bilateral internal auditory canal stenosis measuring 1.3 mm along their max diameter on each side, respectively, with poor delineation (hypoplasia) of the vestibulocochlear nerves in the IAC on both sides.
Normal inner ear structures on both sides.
CT shows diminished IAC diameters measuring 1.3mm on the mid-portion of the IAC on each side respectively (less than 2 mm)
Normal inner ear structures.
Normal labyrinthine segments and normal course of both facial nerves.
Case Discussion
Internal auditory canal (IAC) stenosis 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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