Intraoperative Monitoring of the Cochlear Nerve during Vestibular Schwannoma Surgery

Neurofibromatosis type 2 causes degradation of cochlea and or cochlear nerve function. Auditory brainstem implantation, a technique that relies on direct cochlear nucleus stimulation, offers the possibility of a degree of hearing restoration for patients who would otherwise be bilaterally profoundly deaf. Cochlear implantation is a superior method of hearing restoration but relies on a functioning cochlear nerve. Currently it is not possible to tell whether patients have suffered a cochlea loss alone that would enable cochlear implantation, or a cochlear nerve loss that would necessitate auditory brainstem implantation. For this reason, patients receive an auditory brainstem implant as it guarantees some function.

Our study describes an electrophysiological technique for recording cochlear nerve action potentials (CNAPs) to direct cochlear nerve stimulation for the assessment of cochlear nerve function during vestibular schwannoma removal. The technique will enable real-time assessment of cochlear nerve function during tumor resection, and the appropriate selection of implant at the same sitting. It will offer significantly better hearing rehabilitation for patients with a devastating disease that causes progressive patient isolation.