Sympathetic skin response in patients with multiple sclerosis compared with patients with spinal cord transection and...

In 28 patients with definite multiple sclerosis (MS) and 21 patients with a functionally complete transection of the spinal cord sympathetic skin responses (SSR) from both the palms and soles were studied. In the patients with a complete transection at T3 or 4, SSRs were impaired in the palms as well as the soles, and most patients with a transection at T11 or T12 had normal SSRs in the soles. These findings indicate that the central pathway mediating the SSR descends to the upper thoracic cord where connections are made with the sympathetic distribution to the palms, and then to the lower thoracic cord to reach the sympathetic outflow to the soles. This is compatible with the anatomical knowledge of the sympathetic system. Of the MS patients, 75% had abnormal SSR results. The SSR for the soles was more sensitive than that for the palms. The incidence of SSR abnormality was as high as those of somatosensory evoked potential (SEP) (79%) and visual evoked potential (VEP) (75%) abnormalities. Of the patients with normal SEPs 14% had impaired SSRs and 21% had abnormal SSR with normal VEPs. When the results of these 3 tests were combined, the abnormality increased to 100%. From our study, the SSR probably reflects not only postganglionic sympathetic activity but also preganglionic function. The SSR is therefore useful in evaluating myelopathy, providing information different from that given by assessment of the somatic nervous system. Since the SSR detected a few MS lesions which were not demonstrated by other evoked potentials, it is potentially a new tool for the detection of MS lesions in addition to conventional evoked potential studies.