Use of supramaximal stimulation to predict facial nerve outcomes following vestibular schwannoma microsurgery: Results from a decade of experience - Clinical article

William R. Schmitt, Jasper R. Daube, Matthew L. Carlson, Jayawant N. Mandrekar, Charles W. Beatty, Brian A. Neff, Colin L. Driscoll, Michael J. Link

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Object. The goal of vestibular schwannoma surgery is tumor removal and preservation of neural function. Intraoperative facial nerve (FN) monitoring has emerged as the standard of care, but its role in predicting long-term facial function remains a matter of debate. The present report seeks to describe and critically assess the value of applying current at supramaximal levels in an effort to identify patients destined for permanent facial paralysis. Methods. Over more than a decade, the protocol for stimulating and assessing the FN during vestibular schwannoma surgery at the authors' institution has consisted of applying pulsed constant-current stimulation at supramaximal levels proximally and distally following tumor resection to generate an amplitude ratio, which subtracted from 100% yields the degree to which the functional integrity of the FN "dropped off" intraoperatively. These data were prospectively collected and additional variables that might impact postoperative FN function were retrospectively reviewed from the medical record. Only patients with anatomically intact FNs and > 12 months of follow-up data were analyzed. Results. There were 267 patients available for review. The average posterior fossa tumor diameter was 24 mm and the rate of long-term good (House-Brackmann Grade I-II) FN function was 84%. Univariate logistic regression analysis revealed that prior treatment, neurofibromatosis Type 2 status, tumor size, cerebellopontine angle extension, subjectively thinned FN at the time of operation, minimal stimulation threshold, percent dropoff by supramaximal stimulation (SMS), and postoperative FN function all correlated statistically (p < 0.05) with long-term FN function. When evaluating patients with significant FN weakness at the time of hospital discharge, only the percent dropoff by SMS remained a significant predictor of long-term FN function. However, the positive predictive value of SMS for long-term weakness is low, at 46%. Conclusions. In a large cohort of patients, the authors found that interrogating intraoperative FN function with SMS is safe and technically simple. It is useful for predicting which patients will ultimately have good facial function, but is very limited in identifying patients destined for long-term facial weakness. This test may prove helpful in the future in tailoring less than grosstotal tumor removal to limit postoperative facial weakness.

Original languageEnglish (US)
Pages (from-to)206-212
Number of pages7
JournalJournal of neurosurgery
Volume118
Issue number1
DOIs
StatePublished - Jan 1 2013

Keywords

  • Acoustic neuroma
  • Electrophysiological monitoring
  • Facial nerve
  • Vestibular schwannoma

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology

Fingerprint Dive into the research topics of 'Use of supramaximal stimulation to predict facial nerve outcomes following vestibular schwannoma microsurgery: Results from a decade of experience - Clinical article'. Together they form a unique fingerprint.

  • Cite this