Monitoring spinal cord motor and somatosensory evoked potentials in anesthetized primates.
Monitoring Motor Evoked Potential (MEP) to Transcranial Stimulation (TMS) monitoring (MEP) is a growing technique to assess motor function under anesthesia. The following primate study was conducted to analyze the non-myogenic spinal motor and sensory volleys and to examine their reproducibility under nitrous oxide-methohexidone anesthesia. The traveling periodic spinal descending MEP to TMS and ascending somatosensory (SEP) to posterior tibial nerve stimulation across the thoracic cord were recorded in 12 cynomolgus monkeys. Through a small T11-T12 laminotomy, an insulated stainless steel electrode was inserted into the epidural thoracic space. The potentials were analyzed under 50 vol% NO in O2 with methohexital (0.1-0.2 mg kg-1 min-1). A well-defined periodic TMS-MEPs and PTN-SEPs were recorded with high reproducibility and consistency in repeated trials under N2O-methohexital anesthesia. MEP tracing consisted of an initial peak (direct (D) wave), occurring at 2.43 (+/- 0.28) msec followed by subsequent five positive (indirect (I) waves). Spinal SEPs-MEPs were clearly defined, morphologically stable, and consistent over time under N2O-methohexitone anesthesia. The present primate study may set a model to monitor both modalities in anesthetized neurosurgical patients.
Ghaly
R F
RF
Chicago Institute of Neurosurgery and Neuroresearch, Department of Anesthesiology and Pain Management, IL 60614, USA.
Stone
J L
JL
Lee
J J
JJ
Ham
J H
JH
Levy
W J
WJ
D000768:Anesthesia, General / Q000379:methods; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D004567:Electrodes, Implanted; D055590:Electromagnetic Phenomena / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D008251:Macaca; D012121:Respiration, Artificial / Q000379:methods; D013116:Spinal Cord / Q000502:physiology*; D013979:Tibial Nerve / Q000502:physiology