Motor neuron diseases are not exclusively motor; the SSR paradigm

Motor Neuron Diseases (MNDs), familial and sporadic, are progressive neurodegenerative disorders that, for an extended period in the past, were considered purely motor disorders. During the course of the disease, however, some patients exhibit concomitant non-motor signs; thus, MNDs are currently perceived as multisystem disorders. Assessment of non-motor symptoms is usually performed clinically, although laboratory tests can also be routinely used to objectively evaluate these symptoms. Sympathetic Skin Response (SSR) is an example of a neurophysiological test that has been used in cases of Amyotrophic Lateral Sclerosis, Spinal Muscular Atrophy, and Monomelic Atrophy, mostly to assess Autonomic Nervous System (ANS) disorders. Dysautonomia affects quality of life and life expectancy, as it is involved in cardiovascular events and incidents of sudden death. SSR abnormalities are present even in subclinical involvement of the ANS in MNDs. In this review, we present published research examining SSR findings in various MNDs, and discuss the correlation of SSR findings with clinical symptoms and disease severity, as well as the potential sources of abnormal findings. The aim of this study is to raise clinician awareness of autonomic dysfunction in MNDs and present the benefits of SSR examination in patient care.