title: Role of Facial Nerve Motor-Evoked Potential Ratio in Predicting Facial Nerve Function in Vestibular Schwannoma Surgery Both Immediate and at 1 Year.
abstract: To determine whether transcranial electrical stimulation-induced facial motor-evoked potential (FMEP) monitoring of the facial nerve (FN) during vestibular schwannoma (VS) tumor resection can predict both immediate and 1 year postoperative FN functional outcome.
  
  
  
  Prospective consecutive non-comparative observational case series.
  
  
  
  Tertiary referral center.
  
  
  
  Facial function, immediate post operation and at 1 year using House-Brackmann (HB) grading scale.
  
  
  
  The study included 367 consecutive patients (men 178; women 189; age 13-81 years) monitored during primary sporadic VS microsurgery between November 2002 and April 2015. Neurofibromatosis type II, revision surgery, previous radiotherapy treatment, preoperative facial nerve weakness, and non-VS cases were excluded retrospectively during analysis of data. Data of facial function were missing from eight patients at 1 year and were excluded. The correlation between the final-to-baseline FMEP ratio and immediate and 1 year facial nerve function was examined.
  
  
  
  Using logistic regression model, the cut-off points of FMEP ratio were 0.62 (PPV 0.96) and 0.59 (PPV 0.98) which predicted satisfactory FN function (HB grades 1 or 2) immediately postoperative and at 1 year after surgery, respectively.
  
  
  
  Transcranial electrical stimulation FMEP is a valuable tool for monitoring facial nerve function during resection of vestibular schwannoma. Maintaining a FMEP event-to-baseline ratio of 60% or greater is predictive of satisfactory long-term FN function.
authors.affiliation: *Division of Otolaryngology-Head & Neck Surgery†Division of Neurosurgery, Department of Surgery, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Sanjiv K
authors.initials: SK
authors.lastname: Bhimrao
authors.forename: Trung N
authors.initials: TN
authors.lastname: Le
authors.forename: Charles C
authors.initials: CC
authors.lastname: Dong
authors.forename: Serge
authors.initials: S
authors.lastname: Makarenko
authors.forename: Sarin
authors.initials: S
authors.lastname: Wongprasartsuk
authors.forename: Brian D
authors.initials: BD
authors.lastname: Westerberg
authors.forename: Ryojo
authors.initials: R
authors.lastname: Akagami
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology; D005154:Facial Nerve / Q000502:physiology* / Q000601:surgery; D020220:Facial Nerve Injuries / Q000503:physiopathology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D008297:Male; D008866:Microsurgery; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000601:surgery*; D011183:Postoperative Complications / Q000517:prevention & control; D011446:Prospective Studies; D012189:Retrospective Studies; D055815:Young Adult