Somatosensory evoked potentials(SEPs)were recorded simultaneously from the cervical spine and scalp in 10 normal subjects and 22 patients with cerebrovascular attack(9)and syringomelia(13)using median nerve stimulation.Patients were considered as having abnormal studies

if either N_(18) were absent or if their peak latencies were prolonged more than 21.1 msec

or if the difference of (N_(13)-N_(18))conduction time was more than 7.53 msec.In addition

side-to-side value for(N_(13)-N_(18))were compared

these normally differ by less than 1.38 msec. The results may be summarized as followings: Acupuncture caused a reapperance of N_(18) in patients with absence of N_(18) and a decrease of the prolonged peak latencies by less than the upper limit of normal. Acupuncture obviously integrate the imbalance of side-to-side value for(N_(13)-N_(18))into normal range. Acupuncture exerted no significant effect on the SEPs of normal subject and patients without SEPs abnormalities.