ms. In 5 of them (28%), SSR of the hand was delayed. SSR of the foot was absent on 9 (50%) right and 10 (56%) left legs. The others exhibited a mean latency of 2.47 Β± 0.35 ms on the right foot and 2.34 Β± 0.22 ms on the left. In 5 of them (28%) the response was delayed on the right foot and in 3 (17%) on the left. The SSR was abnormal both in the palms and in the soles in 7 (39%) MS patients (in 1 unilateral) and never isolated in the hands. The amplitudes are less reliable and, due to great variability, were neglected. Therefore we do not consider an asymmetric response to be abnormal, though it may be an important observation. The R-R interval variation was diminished in 6 patients (33%); in 1 (6%) the value was equivocal. Abnormalities in cardiovascular function are known to occur only rarely.
We agree that the interpretation of pathological SSR remains problematic. According to our study, abnormal SSR more consistently and earlier indicates subclinical lesions of the autonomic nervous system (SSR was abnormal in all patients with diminished R-R interval variation, except in 1). In all patients motor and sensory conduction studies were normal.
Multiple sclerosis patients are prone to develop autonomic disturbances. The impairment is frequently silent. The SSR is proved to be a valuable objective test for evaluation of autonomic function.