Multichannel facial nerve monitoring: value in detection of mechanically elicited electromyographic activity and prediction of postoperative outcome

• Published in: Otology & neurotology Vol. 35; no. 7; p. 1290
• Main Authors: Ashram, Yasmine A, Badr-El-Dine, Mohamed M K
• Format: Journal Article
• Language: English
• Published: United States 01.08.2014
• Subjects: Adolescent; Adult; Aged; Electromyography; Facial Nerve - physiopathology; Facial Nerve - surgery; Female; Humans; Male; Middle Aged; Monitoring, Intraoperative - methods; Neuroma, Acoustic - physiopathology; Neuroma, Acoustic - surgery; Postoperative Period; Prospective Studies; Treatment Outcome; Young Adult
• ISSN: 1537-4505
• DOI: 10.1097/MAO.0000000000000441

To determine the value of using a multichannel facial nerve (FN) monitoring setup in detecting mechanically elicited EMG activity during vestibular schwannoma (VS) surgery. Prospective study. Tertiary referral center. This study was conducted on 42 patients operated for VS removal. The FN was monitored using a 5-channel setup with electrodes inserted in mentalis, o.oris, nasalis, o.oculi, and frontalis. The number of channels activated simultaneously in response to a particular event was recorded together with the amplitude of response on each muscle. EMG activity occurring simultaneously on all 5 channels was referred to as "all-channels activity." Postoperative FN function was assessed immediately and 1 year postoperatively using the House-Brackmann classification. The 5-channel setup detected a significantly higher number of mechanically elicited EMG activity than would have been possible using a 2-channel setup. The number and amplitude of EMG activity detected on the mentalis muscle was significantly higher compared with other muscles. Patients with higher percentage of events in which the mentalis fired while o.oris and o.oculi did not were more likely to develop a better long-term outcome. Positive correlation was found between the number of all-channels activity and postoperative outcome (p < 0.001). The use of a multichannel setup allowed earlier and efficient detection of mechanically elicited EMG activity. Including the mentalis muscle significantly increased the detection rate, which tended to reflect as improvement in the long-term outcome. The occurrence of all-channels activity should be considered a prompt warning sign.