Motor Evoked Potentials and Recovery of Motor Function in Spinal Cord Injuried Rats

ABSTRACT

Electrical monitoring of the nervous system offers the potential for the detection of injury and diagnosis of disease. Existing evoked potentials monitor one or another sensory modality, but no generally usable motor monitor exists. Recovery rates of motor function in rats with spinal cord injury were comparetively observed by MEP (Motor Evoked Potential) recorded in 20 spinal cord injured rats and 10 control from distal portion of the injury during stimulation of the cerebral motor cortex. Experimental animals were divided into 10 control and 20 spinal cord injury group which were 10 rats received 20 gcm using weight drop method injury and 10 rats received 50 gcm injury to the spinal cord injury. The relationship of changes in MEQ measured pre-and post-injury respectively and a recovery rats of motor function was analysed and obtained the following results. 1) In postinjury MEP by 20gcm spinal cord-injury rats, 28% latency increase (11.4+/-1.33 msec, control 8.25+/-1.01 msec) and 14% amplitude decrease (17.77+/-7.7 microV, control 20.70+/-2.71 microV) were noted in the recording at 1 week after the injury. However, with the passage of time MEP showed improvement in latency and amplitude. In 50 gcm spinal cord-injury group, 76% latency increase (14.49+/-1.48 msec) and 65% amplitude decrease (6.70+/-2.21 microV) were observed and the latency and amplitude were not improved with the passage of time. 2) A recovery rate of motor function in the injury group was noted to be slowly increased after injury to the spinal cord in 20 gcm spinal cord-injury group, however there was no recovery of motor function in the 50 gcm spinal cord-injury group. 3) Histological examination demonstrated that ecchymotic hemorrhage was found in less than 25% of the cord in 20 gcm spinal cord-injury group, however, approximately 50% of the cord was noted to have ecchymosis and distruption of the neural tissue in 50 gcm spinal cord-injury group. MEP is probably sensitive in the detection of motor dysfunction after spinal cord injury, and clinically whenever MEP showed an improvement, recovery of motor function was followed. MEP might be clinically an important indicator for the prediction of motor function recovery in the patients with spinal cord injury.