Perioperative Recording of Cochlear Implant Evoked Brain Stem Responses After Removal of the Intralabyrinthine Portion of a Vestibular Schwannoma in a Patient with NF2.

Abstract

To predict and optimize hearing outcomes with a cochlear implant (CI) in patients with intracochlear schwannoma and neurofibromatosis type 2 (NF2). A patient with NF2 and bilateral deafness. The intracochlear portion of a vestibular schwannoma was removed with a partial cochleoectomy. During the procedure, a CI was implanted. Perioperatively, electrically evoked auditory brainstem responses (eABRs) were recorded with a novel intracochlear, CI-evoked, broad band stimulus to support the decision to implant a CI. We found positive eABR responses, with thresholds at around the 200 current level. The eV wave was discernible at all stimulated electrodes, with a prolonged latency of about 6.5 ms. The eIII wave was detected at electrodes 9 and 13, with a latency of 4.5 ms. The acoustic reflex was detectable at all stimulated electrodes. Subjective auditory perception could be achieved by stimulating 3 days after surgery. In open-set word recognition, the patient achieved 60% recognition of monosyllables after the first audio processor fitting and 100% 1 month later. After a partial cochleoectomy, this method may serve as a peri-operative, objective assessment of cochlear nerve integrity that could potentially impact the prediction of CI performance. Potential future applications might be assessments of cochlear nerve integrity in patients with inner ear malformations, radiologically suspected cochlear nerve deficiencies, and resected or irradiated spontaneous vestibular schwannomas or NF2.