Change of muscle motor-evoked potentials after motor cortex stimulation caused by acute spinal cord injury in cats.

The validity of the evoked compound muscle action potential (ECMAP) as an index of spinal cord injury has not been established in neurophysiologic monitoring of motor function, although evoked spinal cord potential (ESCP) has been. In the current study, nine cats were used. After craniotomy, electric stimuli were applied to the motor area. Four cats were given stimulation of various numbers and frequencies, and the other five cats underwent graded compression of the spinal cord, and then ECMAPs and ESCPs were recorded. Three cats were awakened and their motor functions were assessed 3 weeks later. The amplitude of the ESCP never decreased to 60% or less of the control value, even when ECMAPs disappeared. No motor dysfunction was present 3 weeks after the experiment. ECMAP is clinically useful, providing information on impairments of the spinal cord that otherwise would remain undetected.