Intraoperative Facial Nerve Monitoring (IFNM) Predicts Facial Nerve Outcome after Resection of Vestibular Schwannoma

Abstract Aim To evaluate the effectiveness of multi-channel electromyographic monitoring of the facial nerve in improving the detection of mechanically elicited EMG activity and providing new predictive criteria for post-operative facial nerve function. Method The Study was conducted on 20 patients undergoing vestibular schwannoma resection in a tertiary referral cerntre. All patients were subjected to facial nerve monitoring during the surgery by a 5-channel setup monitoring the frontalis, O.oculi, nasalis, O.oris, and mentalis muscle. Mechanically elicited EMG activities of the monitored facial muscles were recorded for analysis. After tumour removal, the facial nerve was stimulated proximal to the tumour site using two different types of probes: Prass and flush-tip. Post-operative facial nerve function was assessed using House-Brackmann scale immediately post-operatively and after six months and correlated to the study tested parameters. Results The use of 5-channel montage led to significantly higher sensitivity in detecting mechanically elicited EMG activity than would have been possible with the ordinary 2-channel one. Mentalis muscle showed significantly higher number and amplitude of spontaneous EMG activities than other facial muscles. Positive correlation was found between the proximal threshold and the post-operative facial nerve outcome. The Prass stimulator showed significantly lower threshold than the ball-tip probe. Conclusions The use of multi-channel facial nerve monitoring allowed earlier and more efficient monitoring of the facial nerve. The use of the Prass stimulator is more accurate and correlates more with the real threshold needed for post-resection stimulation of the facial nerve than the ball-tip.

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Prognostic factors for the incidence and recovery of delayed facial nerve palsy after vestibular schwannoma resection

Journal of Neurosurgery ◽

10.3171/2010.5.jns091854 ◽

2011 ◽

Vol 114 (2) ◽

pp. 375-380 ◽

Cited By ~ 16

Author(s):

Ryan P. Morton ◽

Paul D. Ackerman ◽

Marc T. Pisansky ◽

Monika Krezalek ◽

John P. Leonetti ◽

...

Keyword(s):

Prognostic Factors ◽

Facial Nerve ◽

Vestibular Schwannoma ◽

Facial Palsy ◽

Late Onset ◽

Postoperative Recovery ◽

Nerve Monitoring ◽

Facial Nerve Monitoring ◽

Patient Groups

Object Preservation of facial nerve function in vestibular schwannoma (VS) resections remains a significant operative challenge. Delayed facial palsy (DFP) is one specific challenge yet to be fully elucidated. The aim of this study was to evaluate DFP among VS resection cases to identify significant prognostic factors associated with its incidence and clinical recovery. Methods This investigation involves a retrospective review of 104 cases of VS resection that occurred between December 2005 and May 2007. Patients who developed DFP were compared with patients exhibiting no facial palsy postoperatively with regard to surgical approach, severity and day of palsy onset, tumor size, intraoperative facial nerve monitoring, and postoperative recovery and treatment. Patients who demonstrated immediate facial palsy (IFP) following VS resection were also analyzed. Furthermore, specific analyses were performed in 2 distinct DFP patient groups: those who developed DFP after postoperative Day 3 (“late onset DFP”), and those whose palsy worsened after initial DFP identification (“deteriorators”). Results Of the 104 patients who underwent VS resection, 25.0% developed DFP and 8.6% demonstrated IFP postoperatively. The DFP group did not differ significantly in any measure when compared with patients with no postoperative facial palsy. However, patients with DFP presented with significantly smaller tumor sizes than patients with IFP. This IFP group averaged significantly smaller intraoperative facial nerve responses than patients without facial palsy, and larger tumor sizes than both the DFP and no facial palsy groups. Within the DFP group, patients with late onset DFP showed diminished intraoperative facial nerve responses when compared with the total DFP patient population. In total, 25 (96.2%) of 26 patients with DFP and 7 (77.8%) of 9 patients with IFP recovered to normal or near-normal facial function (House-Brackmann Grade I or II) at longest clinical follow-up. Conclusions Although patients with DFP did not exhibit any distinguishable characteristics when compared with patients without postoperative facial palsy, our analysis identified significant differences in patients with palsy presenting immediately postoperatively. Further study of patients with DFP should be undertaken to predict its incidence following VS resection.

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