Monitoring Cochlear Nerve Integrity During Vestibular Schwannoma Microsurgery in Real-Time Using Cochlear Implant Evoked Auditory Brainstem Response and Streaming Neural Response Imaging

Objective:Intraoperative far-field auditory brainstem response (ABR) and direct cochlear nerve action potential monitoring using neural response imaging (NRI) are techniques for monitoring the cochlear nerve during vestibular schwannoma (VS) surgery. A new paradigm has developed where the cochlear nerve is anatomically preserved during tumor removal to facilitate cochlear implantation in select circumstances. This report describes the use of an unmodified commercial cochlear implant (CI) to elicit electrically-evoked direct cochlear nerve and far-field ABR monitoring to evaluate the status of the cochlear nerve during tumor resection in real time.Patients:Adult female with unilateral, sporadic VS.Intervention(s):Cochlear implantation followed by translabyrinthine resection of VS in single operation.Main Outcome Measures:During tumor resection intra-cochlear electrodes were used to deliver electrical stimulation and measure NRI or the cochlear nerve action potential. Electrically-evoked ABR (eABR) was measured using surface electrodes and wave V was monitored (far-field ABR) during surgery.Results:A 61-year-old female was evaluated for a unilateral, enlarging intracanalicular VS with asymmetric SNHL. The patient opted for microsurgery and due to her bilateral hearing loss was a candidate for CI. Cochlear implantation with an unmodified, commercially available lateral wall electrode was performed. The remainder of the approach and tumor resection was performed under continuous eABR and NRI monitoring. Gross total resection was achieved with intact eABR and NRI at the conclusion of the case. Changes in ABR and NRI consistently recovered after modifying dissection strategy. The patient reported auditory percepts with her cochlear implant postoperatively.Conclusions:This report demonstrates the feasibility of using real-time NRI and eABR with a CI to facilitate preservation of the cochlear nerve during VS microsurgery. Using this method to mitigate cochlear nerve trauma during microsurgery may preserve the option of CI for hearing rehabilitation.