Autonomic nervous system function in multiple sclerosis

Autonomic dysfunction causes significant disability in patients with multiple sclerosis (MS). Abnormalities of bladder, bowel and sexual function have been well documented in previous studies but cardiovascular and sudomotor autonomic changes have been less frequently reported. The present study has documented autonomic symptoms and results of cardiovascular and sudomotor autonomic function tests in 63 MS patients and correlated these changes with the clinical features of MS.Autonomic symptoms were common in MS patients, the most common being disorders of micturition, impotence, sudomotor and gastrointestinal disturbances, which were associated with increased MS severity. There was no significant association between autonomic symptoms and abnormalities of autonomic investigations. Abnormalities of one or more autonomic function tests, not including those of bladder, gastrointestinal or sexual dysfunction, were present in more than one half of the MS patients. Autonomic dysfunction, defined as abnormalities in two or more tests, was found in 18% of patients and was associated with increased MS severity. Postural hypotension was very uncommon. Parasympathetic cardiovascular autonomic abnormalities occurred in 16% of patients and were associated with increased MS severity. Sympathetic cardiovascular abnormalities were present in 13% of patients and showed no significant association with MS severity. The sympathetic skin response(SSR) was abnormal in nearly one half of the patients and also showed no significant association with MS severity. There was a variable and heterogenous pattern of autonomic test abnormalities found in the MS patients, which were of minor clinical significance except for postural hypotension. Cardiovascular and sudomotor autonomic abnormalities in MS patients are likely to be due to plaques distributed throughout the brainstem and spinal cord affecting anatomically widespread autonomic regulatory areas and their connections.