[The pain components of somatosensory evoked potentials induced by median nerve stimulation P200-N300].

The pain components of somatosensory evoked potentials (SEPs) of induced by median nerve stimulation were studied with the way of blocking bloodstream of arm in 12 normal adults. The SEPs following the painful stimuli (0.1 msec. square wave pulse) of the right wrist were recorded from the left parietal (C3') and frontal (F3) scalp with earlobe reference electrode. The pressure of 40 mmHg above the arterial pressure was given to the right upper arm by sphygmomanometer. The result showed that the P200-N300 components (latency 234 +/- 13 msec. and 308 +/- 23 msec.) of the SEPs persisted and the others disappeared when tactile sensation disappeared but pain existed. The morphology of P200-N300 from F3 was same to that from C3'. It suggested the P200-N300 were the pain potentials of median nerve SEPs.