Chapter 7 . 1 Sympathetic skin response

The sympathetic skin response (SSR) is a change in skin potential following arousal stimulation, ®rst described by Tarchanoff (1890). SSR is a polysynaptic re ̄ex that is activated by a variety of afferent inputs. The ®nal efferent pathway involves preand postganglionic sympathetic sudomotor ®bers and ultimately activation of sweat glands by the sympathetic out ̄ow. The re ̄ex is coordinated in the posterior hypothalamus, upper brain-stem reticular formation and spinal cord. Thus, central or peripheral lesions of the sudomotor system can impair the SSR. The morphology of the SSR is variable and the potentials may be either mono-, bi-, or triphasic. The SSR has been advocated as simple means of assessing sympathetic sudomotor out ̄ow in central and peripheral nervous system disorders. However, the correlation of an abnormal SSR with more generalized abnormalities of sympathetic sudomotor dysfunction, autonomic dysfunction or small ®ber sensory neuropathy is often poor. Physiological background