Direct cochlear nerve monitoring: First report on a new atraumatic, self-retaining electrode

Objective: To assess the efficacy and safety of a new autraumatic, self-ret aining cranial nerve electrode for direct cochlear nerve monitoring during cerebellopontine angle surgery. Study Design: Prospective clinical investigation. Setting: The Skull Base Surgery Center at Kaiser Permanente, San Diego, a t ertiary referral center for neurotologic and skull-base surgery within Sout hern California Permanente Medical Group. Patients: Eighteen patients, with aidable preoperative hearing, underwent d irect cochlear nerve monitoring with this new electrode during cerebellopon tine angle surgery for a variety of diagnoses. Methods: Intraoperative observations of cochlear nerve action potential amp litude and latency were recorded. Preoperative and I-month postoperative au diograms were compared to assess the degree of hearing preservation. Postop erative facial nerve function was assessed using the House-Brackmann method . Results: Good auditory function was preserved in four of eight acoustic tum ors, with poor hearing preserved in two additional patients. Good auditory function was preserved in the remaining ten patients. Cochlear nerve action potential amplitudes between 5 and 70 mu V were recorded. Postoperative fa cial nerve function was House-Brackmann class I-LI in all 18 patients. Conclusion: The authors find this new electrode to be safe and effective fo r monitoring cochlear nerve function during cerebellopontine angle surgery.