[Comparative study of the nociceptive reflex and late components of the evoked somatosensory potential during stimulation of the sural nerve in healthy subjects].

A study was carried out with 10 normal volunteers in order to find a correlation between nociceptive flexion reflexes from the biceps femoris muscle and the amplitude of the late component (N150-P220) of the vertex evoked potential elicited by sural nerve stimulations at various intensities randomly delivered. The range of stimulus varied from the perception threshold (usually 1 mA) to 2 times the reflex threshold. This latter parameter was usually found between 8 and 11 mA. While the nociceptive flexion reflex increased linearly as a function of stimulation intensity, the amplitude of N150-P220 was maximum at pain threshold and remained in plateau at this level or even slightly decreased as a function of stimulus intensity. No significant correlation was found between the recruitment curve of the nociceptive reflex and that of the late component of the evoked potential as a function of stimulus intensity. Functional implications of these data are discussed.