[Routine study of somatosensory evoked potentials in healthy persons. I. Median nerve].

The study was performed on 62 healthy volunteers (123 nerves) using standard technical parameters. In every case the median nerve was stimulated at the level of II + III fingers and at the wrist. This enabled us to compare potentials evoked by sensory versus mixed nerve stimulation. It has been shown that a reliable evaluation of the somatosensory system is provided by stimulation of mixed nerve. The following montage seems to be the most useful in routine diagnosis. Erb's point - Erb's point, C VII - Fz, Fz - Shoulder, C3,4 - Fz. Additionally, according to clinical situation. C VII - Shoulder and C II - Fz derivations may be used. The Fz - Shoulder derivation enables to record far-field potentials and to control the effect of Fz reference on the waveform of potentials in order derivations. In the study normal values of the main median nerve SEP parameters are presented.