A comparative study of recording procedures for motor evoked potential signals

Motor evoked potential (MEP) signals serve as an objective measure of the functional integrity of motor pathways in the spinal cord. Hence, they provide a reliable assessment of the extent of spinal cord injury (SCI). There are two methods currently being used for serial MEP recordings in rats: a low-frequency and a high-frequency method. In this paper, we compared the two methods and determined the better method for MEP recordings. We also compared the effect of two anesthetic agents — inhalational isoflurane and intraperitoneal ketamine — on the MEP signals. We found that under ketamine anesthesia, low-frequency stimulation led to more consistent results, while high-frequency stimulation required greater stimulation intensity and was prone to unwanted side-effects including excessive head twitches. We further found that isoflurane anesthesia severely depressed the MEP response for both low-frequency and high-frequency stimulation which rendered the resulting signal unusable.

[1]  K. Sugahara,et al.  Transcranial motor-evoked potentials monitoring can detect spinal cord ischemia more rapidly than spinal cord-evoked potentials monitoring during aortic occlusion in rats , 2007, European Spine Journal.

[2]  M. Fehlings,et al.  Epidemiology, demographics, and pathophysiology of acute spinal cord injury. , 2001, Spine.

[3]  H. Morton,et al.  Stimulation of the cerebral cortex in the intact human subject , 1980, Nature.

[4]  M. Kawaguchi,et al.  Effect of Isoflurane on Motor-evoked Potentials Induced by Direct Electrical Stimulation of the Exposed Motor Cortex with Single, Double, and Triple Stimuli in Rats , 1996, Anesthesiology.

[5]  K. Sugahara,et al.  Myogenic transcranial motor evoked potentials monitoring cannot always predict neurologic outcome after spinal cord ischemia in rats. , 2005, The Journal of thoracic and cardiovascular surgery.

[6]  M. Fehlings,et al.  Motor and somatosensory evoked potentials recorded from the rat. , 1988, Electroencephalography and clinical neurophysiology.

[8]  C. Kalkman,et al.  Spinal cord monitoring: somatosensory- and motor-evoked potentials. , 2001, Anesthesiology clinics of North America.

[9]  R. Hopf,et al.  Serial recording of sensory, corticomotor, and brainstem-derived motor evoked potentials in the rat. , 2001, Somatosensory & motor research.

[10]  R. Nashmi,et al.  Serial recording of somatosensory and myoelectric motor evoked potentials: role in assessing functional recovery after graded spinal cord injury in the rat. , 1997, Journal of neurotrauma.

[11]  R. Simpson,et al.  Corticomotor evoked potentials in acute and chronic blunt spinal cord injury in the rat: correlation with neurological outcome and histological damage. , 1987, Neurosurgery.

[12]  R. Hopf,et al.  The effect of ketamine/xylazine anesthesia on sensory and motor evoked potentials in the rat , 2002, Spinal Cord.