Sudomotor and Cardiovascular Dysfunction in Patients with Early Untreated Parkinson's Disease

Background: According to Braak staging of Parkinson's disease (PD), detection of autonomic dysfunction would help with early diagnosis of PD. Objective: To determine whether the autonomic nervous system is involved in the early stage of PD, we evaluated cardiovascular and sudomotor function in early untreated PD patients. Methods: Orthostatic blood pressure regulation, heart rate variability, skin vasomotor function, and palmar sympathetic sweat responses were examined in 50 early untreated PD patients and 20 healthy control subjects. Results: The mean decrease in systolic blood pressure during head-up tilt in PD patients was mildly but significantly larger than in controls (p = 0.0001). There were no differences between the 2 groups in heart rate variability, with analysis of low frequency (LF; mediated by baroreflex feedback), and high frequency (HF; mainly reflecting parasympathetic vagal) modulation. However, LF/HF, an index of sympatho-parasympathetic balance, was lower in the PD group than in controls (p = 0.02). Amplitudes of palmar sweat responses to deep inspiration (p = 0.004), mental arithmetic (p = 0.01), and exercise (p = 0.01) in PD patients were lower than in controls, with negative correlations with motor severity. Amplitudes of palmar skin vasomotor reflexes in PD patients did not differ from controls. Conclusions: Our study indicates impairment of sympathetic cardiovascular and sudomotor function with orthostatic dysregulation of blood pressure control, reduced LF/HF and reduction in palm sweat responses even in early untreated PD patients.