title: The effects of EEG suppression and anesthetics on stimulus thresholds in functional cortical motor mapping.
abstract: OBJECTIVE
  To investigate the effects of EEG suppression and anesthetics on variability of electrical stimulus thresholds during functional cortical motor mapping, and the possible influences of age, lesion location and pathology.
  
  
  METHODS
  Multivariate regression analysis was performed to study these relationships in 60 cases of successful mapping using the monopolar multipulse train technique.
  
  
  RESULTS
  An increase in the length of EEG "flats" by 1s produced an increase in stimulus threshold by 1.08 mA (p=0.0004). Administration of TIVA (total intravenous anesthesia) or inhalational agents produced an additional increase in threshold by 1.27 mA (p=0.38) or 4.84 mA (p=0.04) respectively, when compared to awake patients.
  
  
  CONCLUSIONS
  Depth of cortical suppression impacts the stimulus thresholds. The effect of TIVA on thresholds is mediated by its effect on cortical excitability. The effects of inhalational agents on thresholds involve their influence on excitability at other levels of the neuraxis.
  
  
  CONCLUSIONS
  The study represents an important step towards building a predictive model for stimulus thresholds. It also improves our understanding of the relationships of anesthetics, EEG burst suppression pattern and age with cortical excitability.
authors.affiliation: Clinical Neurophysiology Division, Department of Neurology, Boston, MA, USA. mvsimon@partners.org
authors.forename: Mirela V
authors.initials: MV
authors.lastname: Simon
authors.forename: Costas
authors.initials: C
authors.lastname: Michaelides
authors.forename: Sonya
authors.initials: S
authors.lastname: Wang
authors.forename: Keith H
authors.initials: KH
authors.lastname: Chiappa
authors.forename: Emad N
authors.initials: EN
authors.lastname: Eskandar
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000777:Anesthetics / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D001931:Brain Mapping; D004056:Differential Threshold / Q000187:drug effects; D004558:Electric Stimulation; D004569:Electroencephalography / Q000187:drug effects*; D004827:Epilepsy / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D007430:Intraoperative Care; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D011300:Preoperative Care; D012189:Retrospective Studies; D015173:Supratentorial Neoplasms / Q000175:diagnosis* / Q000601:surgery; D055815:Young Adult
chemical_list: D000777:Anesthetics; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous