Cochlear nerve aplasia: its importance in cochlear implantation.
OBJECTIVE
The objective of this study was to outline the possible implications and potentially valuable techniques for managing cases in which the neural integrity of the peripheral auditory system is in question.


METHODS
This study was a retrospective case review.


METHODS
A 3-year-old child with a profound blilateral sensorineural hearing loss was assessed for suitability of cochlear implantation. Audiologic tests confirmed that the child met the audiologic criteria for cochlear implantation. Computed tomographic scanning and magnetic resonance imaging were undertaken.


RESULTS
Computed tomographic scanning showed bilateral narrow internal auditory canals. Magnetic resonance imaging showed the absence of the acousticofacial bundle on the left side and possible atrophy of the bundle on the right. After detailed discussion, the parents elected to proceed with implantation on the right ear using the Nucleus mini-22 cochlear implant. Tuning of the device resulted in myogenic facial activity with no electrically stimulated auditory sensation. Postoperative electrophysiologic testing confirmed the presence of a compound muscle action potential only.


CONCLUSIONS
Seven months after implantation, the child was explanted uneventfully. The electrical auditory nerve action potential and the electrically evoked auditory brainstem response, using intracochlear stimulation, are potentially valuable measurements to assess neural integrity before the decision to proceed with implantation is made.
Maxwell
A P
AP
Nottingham Paediatric Cochlear Implant Programme, Ropewalk House, United Kingdom.
Mason
S M
SM
O'Donoghue
G M
GM
D001284:Atrophy / Q000473:pathology; D002675:Child, Preschool; D019929:Cochlear Implantation; D003056:Cochlear Nerve / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000151:congenital / Q000209:etiology / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D012086:Reoperation; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed