title: Intraoperative facial nerve motor evoked potential monitoring during skull base surgery predicts long-term facial nerve function outcomes.
abstract: OBJECTIVE
  This study was designed to clarify whether facial nerve motor evoked potentials (FNMEPs) elicited by transcranial electrical stimulation during skull base surgery are useful for predicting long-term facial nerve function.
  
  
  METHODS
  We analyzed FNMEP findings in 35 patients with skull base tumors. Mean follow-up was 24.4 months. Corkscrew electrodes positioned at C3 or C4 and Cz were used to deliver supramaximal stimuli. FNMEPs were recorded from the orbicularis oculi and oris muscles.
  
  
  RESULTS
  The correlation between the final-to-baseline FNMEP ratio and initial or long-term facial nerve function was examined. Initial post-operative facial nerve function correlated significantly with the FNMEP ratios in the orbicularis oculi (r = -0.53, P < 0.005) and orbicularis oris (r = -0.80, P < 0.001) muscles. The correlations between FNMEP ratios and facial nerve function remained significant during long-term follow-up (orbicularis oculi muscle: r = -0.43, P < 0.05; orbicularis oris muscle: r = -0.71, P < 0.001). All patients in whom the FNMEP ratio in the orbicularis oculi muscles remained above 50% were assigned to the satisfactory facial nerve function (House-Brackmann Grades i and ii) group at the final examination.
  
  
  CONCLUSIONS
  FNMEP monitoring can predict facial nerve function not only immediately after surgery but also long-term.
authors.affiliation: Department of Neurosurgery, Brain Research Institute, University of Niigata, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukuda
authors.forename: Makoto
authors.initials: M
authors.lastname: Oishi
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hiraishi
authors.forename: Akihiko
authors.initials: A
authors.lastname: Saito
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Fujii
mesh_terms: D019054:Evoked Potentials, Motor / Q000502:physiology*; D005154:Facial Nerve / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods*; D011237:Predictive Value of Tests; D019291:Skull Base / Q000294:innervation / Q000502:physiology* / Q000601:surgery*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D016896:Treatment Outcome