Nervus intermedius influences continuous facial nerve EMG-monitoring

Background: In vestibular schwannoma surgery, facial nerve function may be monitored by quantification of A-trains, a specific pathological pattern, using the parameter traintime (1). However, false positive results with high traintime and comparatively mild postoperative functional deficits have been observed (2). This study tries to link this phenomenon to the presence of an anatomically and/or electrophysiologically identifiable Nervus intermedius (NI). Methods: In a consecutive group of 87 patients undergoing vestibular schwannoma surgery, the operative videotapes and electrophysiological data from intermitt…