title: Validity of transcranial motor evoked potentials as early indicators of neural compromise in rat model of spinal cord compression.
abstract: METHODS
  Randomized controlled study of intraoperative transcranial motor evoked potentials (TcMEPs) as early indicators of neural compromise in a rat model of spinal cord compression.
  
  
  OBJECTIVE
  To determine the temporal threshold at which a complete (100%) loss of intraoperative TcMEPs will result in significant postoperative functional deficits.
  
  
  BACKGROUND
  There is controversy about the best TcMEP alarm criteria for intraoperative spinal cord protection. Clinical trials provide some evidence, but randomized controlled trials, which are not feasible in humans, are lacking.
  
  
  METHODS
  Twenty-four adult male Wistar rats were divided into 3 experimental groups according to the length of time that a 100% TcMEP signal loss was maintained; all animals had preoperative functional testing. After surgical placement of a balloon catheter in the thoracic sublaminar space, TcMEPs were recorded while the spinal cord was compressed by balloon inflation. The recordings were terminated after maintaining a 100% TcMEP loss for different time periods (0, 5, or 15 min). Functional behavioral testing was repeated after 24 hours.
  
  
  RESULTS
  Only the groups wherein the catheter was left inflated for 5 or 15 minutes after a complete (100%) loss of TcMEP amplitude showed a significant deterioration in functional testing as compared with preoperative baseline values. Functional testing remained normal for both the control group and the group in which termination of spinal cord compression occurred immediately after a decrease of TcMEP amplitude to 100%. There was a strong correlation between TcMEP amplitude recovery postintervention and functional ability at 24 hours postsurgery.
  
  
  CONCLUSIONS
  If a 100% loss of TcMEP signals is immediately recognized and reversed by rapid removal of the compressive force on the spinal cord, normal postoperative function was observed in this rat model. However, delaying intervention for even 5 minutes can result in significant postoperative functional deficits.
  
  
  METHODS
  N/A.
authors: *IWK Health Centre, Halifax, Nova Scotia, Canada †Department of Surgery, Dalhousie University, Halifax, Nova Scotia, Canada ‡Division of Paediatric Orthopaedics, Sidra Medical and Research Center, Doha, Qatar; and §Department of Physiology & Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada.
authors: Susan H
authors: SH
authors: Morris
authors: Jason J
authors: JJ
authors: Howard
authors: Douglas D
authors: DD
authors: Rasmusson
authors: Ron
authors: R
authors: El-Hawary
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D019054:Evoked Potentials, Motor / Q000502:physiology*; D064795:Intraoperative Neurophysiological Monitoring / Q000379:methods*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function; D013116:Spinal Cord / Q000503:physiopathology*; D013117:Spinal Cord Compression / Q000503:physiopathology*; D013131:Spine / Q000601:surgery*; D013997:Time Factors