Novel continuous and quantitative intraoperative facial nerve-monitoring system for temporal bone lesions

Intraoperative systems for monitoring facial nerve function, in which temporal electrical stimulation is applied to the facial nerve through electrodes, are used in many surgeries requiring facial nerve preservation; however, continuous stimulation or quantitative evaluation of facial nerve function is difficult with this approach. We examined the usefulness of a continuous and quantitative facial nerve-monitoring system for temporal bone lesions by using our experience to modify the existing methods used for cases involving vestibular schwannomas. Retrospective observational study. Department of Otorhinolaryngology-Head and Neck Surgery at our hospital. We modified the electrode placement and examined the usefulness of the modified system under several conditions. The study population consisted of patients who were operated on for temporal bone lesions at our department and underwent continuous nerve monitoring using the modified system. Case details, electrode-placement sites, and facial nerve function data before and after the surgery were obtained and retrospectively evaluated. Electrodes were placed safely during surgery in all cases. No obvious deterioration in facial nerve function was observed, except in one case. The advantages of this system include its ability to perform quantitative intraoperative evaluations and prevent unexpected nerve damage in cases where the facial nerve shows complicated pathways. This monitoring system is useful, even in complex temporal bone surgeries.