Sympathetic Skin Response in Amyotrophic Lateral Sclerosis

Purpose: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive loss of motor neurons, but it is increasingly recognized to be a more disseminated disease. The literature on the involvement of the sympathetic skin response (SSR) in ALS is few. Methods: We reviewed the literature with specific emphasis on SSR in ALS and investigated SSR in 120 patients with sporadic ALS and in 130 age-matched healthy subjects to determine the effects of SSR in ALS patients. The SSR was conducted in all ALS patients and healthy subjects. Results: We found prolonged mean SSR latency in ALS patients, and the mean SSR amplitude is reduced compared with that of control subjects, especially in their low extremities (P < 0.05). The disease duration seems to have little impact on the SSR latency and amplitude (P > 0.05). Yet, whichever arm or leg involved, the overall difference in lower extremity SSR measurements between the two groups is significant (P < 0.05). And there is no correlation between initial manifestation of autonomic nervous impairment and amplitude and latency of SSR (P > 0.05). Conclusions: The SSR impairment occurs mainly in lower extremities, which is earlier than clinical manifestation of autonomic nervous impairment in ALS. This may be a subclinical manifestation of ALS. We hypothesize that these results are caused by damage to the unmyelinated postganglionic fibers in ALS patients.