Multichannel facial nerve monitoring: value in detection of mechanically elicited electromyographic activity and prediction of postoperative outcome.
OBJECTIVE
To determine the value of using a multichannel facial nerve (FN) monitoring setup in detecting mechanically elicited EMG activity during vestibular schwannoma (VS) surgery.


METHODS
Prospective study.


METHODS
Tertiary referral center.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
*Department of Physiology, Faculty of Medicine, University of Alexandria, Alexandria, Egypt; and †Department of Otolaryngology, Faculty of Medicine, University of Alexandria, Alexandria, Egypt.
Yasmine A
YA
Ashram
Mohamed M K
MM
Badr-El-Dine
D000293:Adolescent; D000328:Adult; D000368:Aged; D004576:Electromyography; D005154:Facial Nerve / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009464:Neuroma, Acoustic / Q000503:physiopathology / Q000601:surgery*; D011184:Postoperative Period; D011446:Prospective Studies; D016896:Treatment Outcome; D055815:Young Adult