Normal values of Motor Evoked Potentials by Transcranial Magnetic Stimulation.

Lee, Ho Geun; Kim, Gook Ki; Lim, Young Jin; Kim, Tae Sung; Rhee, Bong Arm; Leem, Won

Original Article

Journal of Korean Neurosurgical Society 1991;20(8): 609-620.

Ho Geun Lee, Gook Ki Kim, Young Jin Lim, Tae Sung Kim, Bong Arm Rhee, Won Leem

Departments of Neurosurgery, College of medicine, Kyung Hee University, Seoul, Korea.

ABSTRACT

Electrical stimulation has been used for evaluating central motor system and deep portion of peripheral nerve, but it was painful. And then magnetic stimulation was introduced recently and used widely because it was painless and easily repeated, compared to electrical stimulation. This study was undertaken in order to obtain normal valued of motor evoked potentials by transcranial magnetic stimulation. Ninety-two volunteers, free of neurological disease, were tested with Medelec Magstim model 200 and Medelec MIstral. There were 55 male and 37 female, ranging in height from 130 to 180 centimeter, with a mean height of 165.9 centimeter, in age from 13 to 70 years, with a mean age of 34 years. Transcranial magnetic stimulation cause contralateral hand and foot muscle responses, and the resultant motor evoked potentials can be recorded. Stimulating sites were near vertex in head, Erb's point in cervical region and L45 interspace in lumbar region. Recording sites wre abductor pollicis brevis(APB) in hand and abductor hallucis(AH) in foot. Our results were as follow ; 1) Latency between head and contralateral APB was 20.9+/-1.5ms, latency between cervical region and ipsilateral APB was 11.7+/-1.1ms, and there-by CMCT was 9.2+/-1.1ms. 2) Latency between head and contralateral AH was 39.0+/-2.6ms, latency between lumbar region and ipsilateral AH was 20.9+/-2.1ms, and there-by CMCT was 1.8+/-2.0ms. 3) Latency was statistically well correlated with subject height, but not CMCT. 4) There was no statistical significance, between male and female, right and left side, among age group, in latency and CMCT. 5) By voluntary muscle contractions, latency was shortened and amplitude was increased on vertex stimulation, but not hanged on stimulation of cervical and lumbar region. 6) By incraesing stimulus intensity, latency was shortened and amplitude was increased on vertex stimulation, but amplitude only was increased on stimulation of cervical region.

Key Words: Transcranial magnetic stimulation; Latency; Motor evoked potentials; Central motor conduction time