Cochlear Implantation in Narrow Duplicated Internal Auditory Canal: Case Report and Systematic Review

Background: Narrow duplicated internal auditory canal (IAC) is a rare congenital malformation frequently associated with severe-to-profound sensorineural hearing loss. Case Presentation: We present a one-year-old girl with bilateral narrow duplicated IAC and profound hearing loss evaluated through CT/MRI and electrically evoked auditory brainstem response (EABR). Methods: We conducted a systematic review (1990–2023), identifying 59 published cases of which 24 were bilateral. The mean age at diagnosis was 10.34 years, and 25 cases presented additional inner ear malformations. Only seven patients underwent cochlear implantation, and EABR was performed in four cases. Outcomes of cochlear implantation were heterogeneous. Discussion: In our case, EABR showed a reproducible wave V on the right side, supporting candidacy for cochlear implantation which led to positive early auditory responses. Conclusions: This case and review highlight the role of EABR in identifying residual cochlear nerve functionality and guiding candidacy for cochlear implantation in narrow duplicated IAC.