Visually Evoked Sympathetic Skin Response in Normal Subjects

ABSTRACT

BACKGROUND: Sympathetic skin response (SSR) is a transient change in the electrical potential of the skin that is evoked by internal or external stimuli. In the present study, our purpose was to compare electrical and visual stimulation methods of evoking a SSR. METHODS: SSRs evoked by both electrical and visual stimulation were recorded from the palm and sole from 48 healthy volunteers. RESULTS: SSRs were obtained in all normal control subjects following both electrical and visual stimulation. The latency of SSR following electrical stimulation was 1383.75+/-223.56 msec at the palm and 1790.54+/-318.70 msec at the sole, and that following visual stimulation was 1518.75+/-252.64 msec at the palm and 1930.10+/-226.19 msec at the sole. The latencies of SSRs following visual stimulation were prolonged significantly more than those following electrical stimulation. The amplitudes of SSRs following visual stimulation were significantly lower than those following electrical stimulation, and the amplitude of SSRs following both electrical and visual stimulation had marked intersubject and intrasubject variabilities in each of the stimulations. CONCLUSIONS: The SSR evoked by visual stimulation is as reliable as known electrical stimulation for determining sympathetic functions and is a less invasive method. Latencies by visual stimulation are longer than those by electrical stimulation in both the palm and sole. The visual stimulation method of evoking a SSR is not influenced by an ascending somatosensory pathway theoretically, so we can postulate that it reflects a purely autonomic function if there is no problem in the visual pathway.