[P22 and N30 of median nerve SSEPs--independence of the frontal waves from parietal waves].

Median nerve short-latency somatosensory evoked potentials (MN-SSEPs) were recorded from the scalp to assess frontal lobe functions in children. Forty-nine patients, aged between three and fifty years old underwent 87 examinations. They were divided into four groups: A (3 to 4 years old); B (5 to 6 years old); C (7 to 15 years old) and D (20 to 50 years old). Stimulus electrodes were placed near the wrist on the median nerve. The study was done mostly in the waking state. To evaluate the independence of the frontal lobe from the parietal lobe we correlated the frontal P22 and parietal N20, and compared the frontal N30 with parietal negative waves. The intervals of the peak latency differed between P22 and N20 by -1.5 to 1.5 msec. Significant differences were noted between groups A and D, and between C and D. N30 and negative parietal waves resembled each other in children 3 to 4 years of age, but became different from 5 years old. They were dissimilar after 6 years old. Therefore, N30 waves were useful for evaluating the frontal elements in children over 5 years of age.