Cardiovascular dysautonomia in de novo Parkinson's disease

BACKGROUND: Clinical symptoms of Parkinson's disease (PD) include not only motor distress, but also autonomic dysfunction. OBJECTIVE: To clarify the progression of autonomic nervous dysfunction in PD. METHODS: The subjects were 44 patients with de novo PD. Autonomic nervous function, including cardiac sympathetic gain, was evaluated on the basis of cardiac radioiodinated metaiodobenzylguanidine (MIBG) uptake, the response to the Valsalva maneuver, and spectral analyses of the RR interval and blood pressure. RESULTS: Decreased cardiac MIBG uptake was found even in patients with early stage PD. MIBG uptake gradually decreased with increased disease severity. Hemodynamic studies using the Valsalva maneuver revealed that patients with early stage PD had reduced baroreceptor reflex sensitivity (BRS) in phase II, but not phase IV. Blood pressures normally rose in phases II and IV, but the increments decreased with disease progression. In early stage PD, the low frequency power of the RR interval (RR-LF) and the ratio (LF/HF) of RR-LF to the high frequency component of the RR interval (RR-HF) were significantly lower than the respective control values, despite no significant difference in RR-HF; these variables decreased with disease progression. CONCLUSION: Our results show that latent sympathetic nervous dysfunction without parasympathetic dysfunction, especially that involving the sinus node, is already present in early stage de novo PD. It is unclear whether the responsible lesion is central or peripheral.