The evoked potential monitoring system has been used to assess the functional integrity of sensory and motor and motor pathways of spinal cord in various spinal cord injuries. Recent studies reported that motor evoked potentials (MEPs) and spinal
cord
evoked potentials (SCEPs) were more sensitive than somatosensory evoked potentials (SSEPs) to evaluate the recovery of motor function after spinal cord injury.
The purpose of this study was to characterize the normal SCEPs elicited by epidural electrical stimulation of the spinal cord, and compare changes of SCEPs with those of MEPs following acute spinal cord injury in Sprague Dawley rats. MEPs were
evoked by
transcranial electrical stimulation of the somatic motor cortex through a stainless steel screw and SCEPs by direct electrical epidural stimulation of C2 spinal cord using bipolar silver ball electrodes. both evoked potentials were recorded from
two
pairs of stainless steel wire which located epidurally at L1 spinal cord. Twenty animals received a 12.5g/cm (n=10), 25g/cm (n=10) weight drop injury of the spinal cord at T10 cord level and ventral or dorsal section of spinal cord was performed
at
T9-T10 levels in other animals (n=6).
@ES The results of the experiment are as followings:
@EN 1. The normal MEPs comprised of reproducible 3 waves, P1, P2, P3, and conduction velocity of each wave was 59.7, 37,5, 20.6m/sec, respectively.
2. The normal SCEPs composed of typical 2 waves, P1, P2, and conduction velocity was 51.4, 17.2m/sec, respectively.
3. P1 wave of SCEPs was abolished following the ventral cord section, whereas P2 wave was abolished by dorsal cord section.
4. Following 12.5g/cm drop injury, reduction of amplitude in SCEPs and MEPs was 34%. 66% of preinjury, which there was significant difference between SCEPs and MEPs (P<0.05).
5. By 25g/cm droup injury SCEPs were abolished in 80% of experimental cases and MEPs in 60%. Also, amplitude was decreased to 48% and 69% of preinjury in SCEPs and MEPs, respectively.
These results suggest that SCEPs result from activation of both dorsal and ventral columns of the spinal cord and that changes of SCEPs are more sensitive than MEPs to acute spinal cord injury caused by weight drop techique.
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