title: Variability in amplitude and stimulation threshold values in motor evoked potential (MEP) monitoring during the resection of brain lesions.
abstract: OBJECTIVE
  Criteria for motor evoked potential (MEP) monitoring include the amplitude criterion and threshold criterion. The aim of our study for the amplitude criterion during removal of brain lesions was to determine a suitable stimulus intensity that can reduce the variability in amplitudes. We also assessed the usefulness of the threshold criterion and amplitude criterion by comparing the variability between the two methods as a preliminary study.
  
  
  METHODS
  Seventeen patients including 12 cases with no neurological deterioration after surgery were enrolled in this study. The amplitudes in various stimulus intensities and the stimulation threshold (ST) were repeatedly measured during surgery. The stimulus intensities used in the amplitude criterion are described as 'the ST just after dura opening (ST(0))+additional intensity'. The variability was assessed with the coefficient of variation (CV).
  
  
  RESULTS
  With direct cortical stimulation (DCS), the CVs of amplitudes were significantly lower at stimulus intensities of more than ST(0)+4 mA, with the smallest at ST(0)+10 mA. The CV of STs was significantly smaller than that of amplitudes.
  
  
  CONCLUSIONS
  The variability in the amplitude criterion was significantly reduced using stimulus intensities of more than ST(0)+4 mA. The variability in the threshold criterion was significantly smaller than that of the amplitude criterion, even when using a strong stimulus intensity.
  
  
  CONCLUSIONS
  The maximal stimulus intensity with no body motion should be used in the amplitude criterion for intraoperative MEP elicited by DCS.
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan; Master's Program in Medical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Emiko
authors.initials: E
authors.lastname: Okamoto
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan. Electronic address: e-ishikawa@md.tsukuba.ac.jp.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Ishikawa
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Masahide
authors.initials: M
authors.lastname: Matsuda
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Nakai
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Matsushita
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Masuda
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Akutsu
authors.affiliation: Department of Health, Faculty of Health Sciences, National University Corporation Tsukuba University of Technology, Tsukuba, Ibaraki, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ayuzawa
authors.affiliation: Department of Clinical Laboratory, University of Tsukuba Hospital, Tsukuba, Ibaraki, Japan.
authors.forename: Fumiko
authors.initials: F
authors.lastname: Sakamaki
authors.affiliation: Department of Clinical Laboratory, University of Tsukuba Hospital, Tsukuba, Ibaraki, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Matsumura
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000502:physiology* / Q000601:surgery*; D046690:Deep Brain Stimulation / Q000379:methods* / Q000592:standards; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
keywords: Glioma surgery; Motor evoked potential; Variability