Real-Time Monitoring of Brainstem Auditory Evoked Response (BAER) during Cerebellopontine Angle (CPA) Surgery

Abstract

The signal-to-noise ratio of brainstem auditory evoked responses (BAER) can be greatly enhanced by use of optimal digital filtering before averaging. This permits accurate assessment of auditory nerve status every 5 to 10 seconds, making real-time intraoperative monitoring possible. The major advantages yielded by real-time monitoring—in our experience thus far—have been (1) identification of potentially adverse functional consequences of apparently uneventful surgical maneuvers, reducing postoperative dysfunction, (2) early indication of potential for improved clinical function, and (3) potential identification and localization of neural tissue in the face of absent surgical landmarks. Examples of these advantages will be provided from case studies, and the possibility that real-time monitoring may improve ability to preserve hearing will be discussed.