Sympathetic skin response in different regions of the palm after median or ulnar nerve injury

Abstract

Objective To explore sympathetic skin response (SSR) in the region innervated only by the median or ulnar nerve. Methods Thirty healthy volunteers, ten patients with median nerve injury, ten patients with ulnar nerve injury and three patients with both median and ulnar nerve injury were involved in the study. SSR was elicited by electrical stimulation and the latency and amplitude of the SSR were recorded in the center of the palm and on the hypothenar, and the pulps of the index and little fingers. Results After median nerve injury the SSR of the index finger pulp disappeared, the SSR amplitude of the palmar center was reduced, while the SSR amplitude of the little finger pulp was normal. In contrast, after ulnar nerve injury the SSR of the little finger pulp disappeared,the SSR amplitude of the hypothenar was reduced, while the SSR of the index finger pulp was normal. When both nerves were injured, no SSR could be elicited anywhere on the palm. Conclusions The SSR of the palmar center and hypothenar are affected by both the median and ulnar nerves. The index and little finger pulps are sites for recording SSR which represent the SSR of the median and ulnar nerve distribution, respectively. Index and little finger pulps are ideal sites for detec t ing efferent functioning of sympathetic nerves from the median and ulnar nerve paths,respectively. Key words: Sympathetic skin response; Median nerve; Ulnar nerve; Nerve injury