Sympathetic skin response in Parkinson's disease before and after mental stress

This study aims to evaluate sympathetic sudomotor activity in Parkinson's disease (PD) by means of the sympathetic skin response (SSR) and explore its possible changes due to mental stress.

Sudomotor function was evaluated using SSR in 29 patients with PD (Hoehn and Yahr stage I-IV) without any clinical evidence of autonomic dysfunction. Twenty-seven healthy matched controls were also evaluated. SSR was elicited by electrical stimulation of the right median nerve and simultaneously recorded on the palms of both hands. Arithmetic mental stress was evoked by means of the WAIS-R arithmetic subscale. Latency and amplitude of SSR were evaluated before and after arithmetic mental stress.

The SSR was obtained in all patients and controls. There were no significant differences in its mean latency and amplitude between patients and controls. SSR parameters were significantly correlated with disease duration, UPDRS score, and disease stage. There were also significant correlations with rigidity and bradykinesia, but not with tremor. Mental stress had no effect on SSR parameters in any group.

SSR parameters in PD without autonomic dysfunction were comparable to matched controls. Although PD patients are sensitive to mental stress, the arithmetic task had no effect on SSR parameters. Consequently, SSR as a method of evaluation of sympathetic sudomotor function is not sufficient for exploration of subclinical autonomic dysfunction in PD, but should be combined with other tests of autonomous nervous system.