[Evoked potentials].

Abstract

Recent advances of evoked potentials, mainly pain-related somatosensory evoked potentials following CO2 laser stimulation (pain SEPs), were summarized. A small negative and a large positive potential, the N240-P340 and the N300-P400 following the hand and the foot stimulation, were identified in normal subjects. Conduction velocity of the A delta fibers and the spinothalamic tract was approximately 10 m/sec. Pain SEPs were significantly decreased in amplitude and the marked pain relief was induced by vibration applied to the area where laser stimulation was applied. This finding was compatible with the gate control theory. Active and passive movements of the limbs remote from and adjacent to the stimulated area significantly decreased pain SEPs in amplitude. This indicated the particular interactions between pain perception and movement-related cortical activities taken place in some areas of the brain. The theory, diffuse noxious inhibitory controls (DNIC) proposed by Le Bars et al., was also confirmed by pain SEPs. Pain SEPs were useful in clinical testing. Pain SEP findings showed a significant correlation with the clinical impairment of pain sensation, and the subclinical lesions of the ascending pathways of the painful sensation were detected by pain SEPs.