title: The cutoff amplitude of transcranial motor-evoked potentials for predicting postoperative motor deficits in thoracic spine surgery.
abstract: METHODS
  Prospective clinical study of intraoperative transcranial motor-evoked potentials (TcMEP) amplitudes and postoperative motor deficits.
  
  
  OBJECTIVE
  To determine the cutoff amplitude during intraoperative TcMEP monitoring for predicting postoperative motor deficits after thoracic spine surgery.
  
  
  BACKGROUND
  Several alarm points when monitoring with TcMEP have been advocated, but there have been no reports on an actual cutoff amplitude of TcMEP for predicting the occurrence of postoperative motor deficits.
  
  
  METHODS
  Among 80 consecutive surgical cases, 28 had a deterioration in TcMEP amplitude in at least 1 monitored muscle during surgery. We examined intraoperative electrophysiological changes and postoperative motor deficits in 270 monitorable muscles in those 28 patients. Through receiver operating characteristic curve analysis, we identified the cutoff amplitudes at the intraoperative point of deterioration and at the end of surgery for predicting postoperative motor deficits in both relative and absolute values.
  
  
  RESULTS
  The relative and the absolute cutoff amplitudes of TcMEP at the intraoperative point of deterioration and at the end of thoracic spine surgery were 12% of control amplitude and 1.9 μV and 25% of control amplitude and 3.6 μV, respectively. Sensitivity/specificity for those cutoff points are 88%/64%, 69%/83%, 90%/64%, and 70%/82%, respectively.
  
  
  CONCLUSIONS
  We determined the cutoff amplitude for predicting postoperative motor deficits in thoracic spine surgery. The results may help establish the alarm criteria for thoracic spine surgery.
authors.affiliation: Department of Orthopedic Surgery, Nagoya University School of Medicine, Nagoya, Aichi, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Muramoto
authors.forename: Shiro
authors.initials: S
authors.lastname: Imagama
authors.forename: Zenya
authors.initials: Z
authors.lastname: Ito
authors.forename: Norimitsu
authors.initials: N
authors.lastname: Wakao
authors.forename: Kei
authors.initials: K
authors.lastname: Ando
authors.forename: Ryoji
authors.initials: R
authors.lastname: Tauchi
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hirano
authors.forename: Hiroki
authors.initials: H
authors.lastname: Matsui
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Matsuyama
authors.forename: Naoki
authors.initials: N
authors.lastname: Ishigro
mesh_terms: D000328:Adult; D000368:Aged; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods* / Q000592:standards; D011183:Postoperative Complications / Q000175:diagnosis* / Q000503:physiopathology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D013904:Thoracic Vertebrae / Q000473:pathology / Q000601:surgery*; D050781:Transcranial Magnetic Stimulation / Q000379:methods* / Q000592:standards; D055815:Young Adult