Magnetic stimulation of the motor system is a new painless, noninvasive neurophysiologic technique enabling examination of the central motor pathways in awake persons.
Fifty five healthy adults were studied.
The mean central motor conduction time w as 5.82 ± 0.67 msec, 6.31 ± 0.39 msec, 6.81 ± 0.61 msec and 13.53 ± 1.52 msec when recording from biceps brachii, extensor digitorum brevis, abductor digiti quinti and tibialis anterior respectively and all those showed no significant difference in both side.
The onset latencies obtained by magnetic root stimulation were always shorter than the peripheral motor conduction time estimated by F-wave study, and the difference is 0.78 ± 0.67 msec in the abductor digiti quinti and 3.01 ± 1.05 msec in the tibialis anterior. And motor evoked potential was not elicited in the tibialis anterior muscle by cervical stimulation. Therefore the origin of the responses in the sine was due to excitation of the peripheral nerves or roots and not spinal cord.
With increment of height, the mean latencies of motor evoked potentials become significantly prolonged (p<0.01), but central motor conduction time showed no change.
