Autonomic functions in the early stages of Parkinson's disease.

Disturbances of autonomic nervous functions are common in patients with Parkinson's disease (PD) and may develop as a result of pathological changes in centers of autonomic regulation such as the hypothalamus, brainstem, and sympathetic ganglia. We examined cardiovascular reflexes using bedside, noninvasive procedures in 20 unmedicated PD patients with early stages of the disease (stage 1 and 2 on the Hoehn and Yahr's scale). Sixteen patients (80%) exhibited some degree of autonomic nervous system dysfunction. These included predominantly cardiovascular functions mediated via the parasympathetic system. Our findings demonstrate: (a) a high prevalence of autonomic disturbances in early stage PD, and (b) that dysregulation of parasympathetic cardiovascular control mechanisms is a major feature of dysautonomia in early, unmedicated PD patients.