Sympathetic skin response: correlation with autonomic and somatic involvement in multiple sclerosis.

The sympathetic skin response (SSR) was studied in 63 multiple sclerosis (MS) patients, 54 with clinical definite and 9 with clinical probable form. The test was recorded from palms and soles and induced by electric stimulus. SSR was abnormal, absent or mildly delayed, in 26 patients (41%). The average score in the Kurtzke Expanded Disability Status Scale was higher in patients with abnormal SSR, showing a positive correlation with the latencies (p < 0.05). When compared to other evoked responses (somatosensory, brainstem auditory and visual evoked potentials), only visual evoked potentials showed a positive correlation (p < 0.05). Among the signs of autonomic dysfunction, bladder impairment was the most frequently associated with altered SSR (p < 0.05). These results could be probably due to the higher incidence of these abnormalities during the course of the disease. It is concluded that SSR is a simple test for a dynamic evaluation of MS, well correlated with the degree of disability, able to detect subclinical lesions in the sympathetic tracts, but with slight localizing value. It has also a low sensitivity for autonomic impairment related only with the bladder dysfunction. These facts exclude the SSR as a primary diagnostic tool in MS.