title: Strategies and Pitfalls of Motor-Evoked Potential Monitoring during Supratentorial Aneurysm Surgery.
abstract: BACKGROUND
  The aims of this study were to reveal the strategies and pitfalls of motor-evoked potential (MEP) monitoring methods during supratentorial aneurysm surgery, and to discuss the drawbacks and advantages of each method by reviewing our experiences.
  
  
  METHODS
  Intraoperative MEP monitoring was performed in 250 patients. Results from 4 monitoring techniques using combinations of 2 stimulation sites and 2 recording sites were analyzed retrospectively.
  
  
  RESULTS
  MEP was recorded successfully in 243 patients (97.2%). Direct cortical stimulation (DCS)-spinal recorded MEP (sMEP) was used in 134 patients, DCS-muscle recorded MEP (mMEP) in 97, transcranial electrical stimulation (TES)-mMEP in 11 and TES-sMEP in 1. TES-mMEP during closure of the skull was used in 21 patients. DCS-mMEP was able to detect waveforms from upper and/or lower limb muscles. Alternatively, DCS-sMEP (direct [D]-wave) could accurately estimate amplitude changes. A novel "early warning sign" indicating ischemia was found in 21 patients, which started with a transiently increased amplitude of D-wave and then decreased after proximal interruption of major arteries. False-negative findings in MEP monitoring in 2 patients were caused by a blood insufficiency in the lenticulostriate artery and by a TES-sMEP recording, respectively.
  
  
  CONCLUSIONS
  The results of this study suggest that to perform accurate MEP monitoring, DCS-mMEP or DCS-sMEP recording should be used as the situation demands, with combined use of TES-mMEP recording during closure of the skull. DCS-sMEP is recommended for accurate analysis of waveforms. We also propose a novel "early warning sign" of blood insufficiency in the D-wave.
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan. Electronic address: ymaruta@yamaguchi-u.ac.jp.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Maruta
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Fujii
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Hirochika
authors.initials: H
authors.lastname: Imoto
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Sadahiro
authors.initials: S
authors.lastname: Nomura
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tanaka
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Inamura
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Sadahiro
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Fumiaki
authors.initials: F
authors.lastname: Oka
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Hisaharu
authors.initials: H
authors.lastname: Goto
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Shirao
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ideguchi
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoneda
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Eiichi
authors.initials: E
authors.lastname: Suehiro
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Koizumi
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Ishihara
authors.affiliation: Department of Neurosurgery, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
authors.forename: Michiyasu
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D009044:Motor Cortex / Q000503:physiopathology*; D012189:Retrospective Studies
keywords: Cerebral aneurysm; direct cortical stimulation; intraoperative monitoring; motor-evoked potential; transcranial electrical stimulation