Motor versus somatosensory evoked potential changes after acute experimental spinal cord injury in rats.

In this study, averaged cortical somatosensory evoked potentials (SEP) after sciatic nerve stimulation, and lower extremity muscle responses after motor cortex stimulation (MEP) were compared in rats. 10 animals served as light (25 g-cm) and 10 animals as severe (80 g-cm) acute spinal cord injury group after weight dropping trauma. After the initial loss of components, both SEP and MEP recovered in most cases in the light injury group. In the severe injury group, however, no recovery was observed in cortical SEPs, while the muscle MEP recovered in some animals. Light spinal cord injury had little effect on muscle MEPs and caused a paradoxical amplitude increase in some MEP recordings. Latency values of muscle MEPs did not show great changes after either kind of injury, while cortical SEP latency was considerably delayed. In this model cortical SEPs were more sensitive to light spinal cord injury than muscle MEPs after single electrical cortical stimuli. Severe spinal cord injury caused amplitude changes or loss of waves from both SEP and MEP.