Intraoperative electromyography and surgical observations as predictive factors of facial nerve outcome in vestibular schwannoma surgery.
OBJECTIVE
To evaluate the predictive value of electromyographic recordings for the immediate facial nerve outcome after solitary vestibular schwannoma (VS) removal.


METHODS
Prospective cohort study.


METHODS
Tertiary referral center.


METHODS
From November 2005 to July 2007, 120 operated solitary VSs monitored by NIM Response 2.0 (Medtronic, Xomed, Jacksonville, FL, USA) were included. Intraoperative direct facial nerve stimulation at the brainstem (proximal pre site) before resection and at the brainstem (proximal post and distal sites, respectively) and internal acoustic meatus after resection were performed. Intraoperative recordings were performed on 4 muscles: Frontalis, Orbicularis oculi, Orbicularis oris, and chin muscles (CM). Postoperative facial function (House-Brackmann classification) was evaluated at postoperative Days (D) 2, 8, and 30. Grades 1 or 2 were considered as a good result.


RESULTS
A good postoperative facial function was obtained in 71, 63, and 77% at postoperative D2, D8, and D30, respectively. Maximal conduction block was found at Day 8. Poor facial nerve outcomes were observed for large tumor with a facial nerve superior to the tumor with a strong adhesion to the nerve. With a stimulation threshold at proximal site after proximal site tumor resection at less than or equal to 0.04 mA, a good facial function was observed in 77% at Day 8. Using these criteria together with CM responses greater than 800 muV to supramaximal stimulation at (proximal post site) and a proximal/distal post ratio at CM response greater than 0.6, 93% of patients presented with a good facial function at Day 8.


CONCLUSIONS
Using CM recording stimulation and supramaximal stimulation of the facial nerve in combination with thresholds seem to increase the predictive value of the monitoring for the immediate facial nerve function for VS surgery.
Bernat
Isabelle
I
AP-HP, Hôpital Beaujon, Otolaryngology Department, Clichy, France.
Grayeli
Alexis Bozorg
AB
Esquia
Gonzalo
G
Zhang
Zhihua
Z
Kalamarides
Michel
M
Sterkers
Olivier
O
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001933:Brain Stem / Q000502:physiology; D004428:Ear Neoplasms / Q000473:pathology / Q000601:surgery*; D004558:Electric Stimulation; D004576:Electromyography; D005154:Facial Nerve / Q000502:physiology; D020220:Facial Nerve Injuries / Q000453:epidemiology* / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009431:Neural Conduction / Q000502:physiology; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D013506:Otologic Surgical Procedures / Q000009:adverse effects*; D011183:Postoperative Complications / Q000453:epidemiology*; D011237:Predictive Value of Tests; D055815:Young Adult