Duplication of the internal auditory canal: radiographic imaging case of the month.

As many as 40% of patients with congenital sensorineural hearing loss will have a structural inner ear malformation identified on a temporal bone imaging study (1). Anomalies of the internal auditory canal (IAC) are rare and have been reported to account for only 12% of all congenital temporal bone abnormalities. Internal auditory canal abnormalities may be associated with hypoplasia or aplasia of the vestibulocochlear nerve with resultant sensorineural hearing loss. Sensitive magnetic resonance imaging (MRI) techniques are able to examine in great detail the anatomy and contents of the IAC and to diagnose aplasia or hypoplasia of the vestibular and/or cochlear nerves (2). Duplication of the IAC is an extremely rare finding involving a redundant bony canal extending from the cerebellopontine angle through the otic capsule bone toward the labyrinth or cochlea. A narrow, duplicated IAC can be associated with congenital sensorineural hearing loss secondary to aplasia of the vestibulocochlear nerve.