Estimation of normal motor conduction velocity of spinal cord by using transcranial electric stimulation and F-wave study.

A non-invasive method for estimation of motor conduction velocity of the spinal cord was performed by transcranial electric stimulation of motor cortex and an F-wave study of the peripheral nerve. Fourty normal persons including 24 men and 16 women ranging in age from 24 to 55 years (mean, 32 years) participated in the study. With a transcortical electric stimulation over the motor cortex, both the conduction time to the contralateral abductor pollicis brevis and the anterior tibial muscles, and the amplitude of the muscle action potentials were recorded. F-wave studies were performed in the median and peroneal nerves. Motor spinal cord conduction velocity (SCCV) was calculated by measuring the distance from 7th cervical to 12th thoracic spinal processes and dividing by the central conduction time obtained by the motor evoked potential studies and the F-wave latencies. The results showed a motor SCCV of 63.3 +/- 8.6 (mean +/- 1 SD) m/sec in all subjects. There was no difference in male and female groups. The conduction time from the motor cortex to the target muscles was not different in both sex groups correlating to the factor of body height. From these results the conclusion was made that the estimation of motor SCCV is measurable and provides valuable data in the detection of electrophysiological function of spinal motor pathways.