Bilateral duplication of the internal auditory canals and bilateral cochlear implant outcomes and review

Objectives: Bilateral duplication of the internal auditory canal (IAC) is rare and is associated with profound sensorineural hearing loss. The present study aims to review our experience with bilateral cochlear implantation (CI) in children with a duplication of the IAC and to review the literature. Methods: The Sydney Cochlear Implant Centre database was searched for children with duplication of the internal auditory canal. Data was collected regarding clinical history, MRI and CT findings, auditory brainstem responses (ABR), tympanometry and otoacoustic emissions (OAE), visually reinforced orientation audiometry, auditory brainstem response, electrocochleography (ECochG), transtympanic electrical auditory brainstem response (ABR), aided cortical evoked potentials (CAEP) and intraoperative neural response telemetry (NRT) and CI evoked electrical auditory brainstem testing. Results: two children with bilateral duplication of the IAC were identified who successfully underwent bilateral cochlear implantation. Audiological development was monitored for 2 and 3 years respectively, both children could spontaneously verbalise and displayed Categories of Auditory Performance (CAP) score of 5 and 6 respectively. Conclusion: Children with duplication of the IAC, with accompanying cochlear nerve dysplasia (CND) can benefit from CI surgery, and verbal receptive and expressive language is possible.