Normal cerebral hemodynamic response to orthostasis in Parkinson's disease

In patients with Idiopathic Parkinson's Disease (IPD) without a history of syncope the cardiovascular and cerebrovascular response to orthostatic stress was studied to search for subclinical impairment of autoregulatory mechanisms. Fifteen patients with IPD and 15 healthy age-matched controls were studied at rest and during head-up tilt (HUT). Heart rate, mean arterial blood pressure (MAP) and mean blood flow velocity (MBFV) in the middle cerebral artery were measured simultaneously. Changes of MAP and MBFV and the relationship between both were assessed. During HUT, heart rate increased less in patients than in healthy subjects (16.3% versus 24.2%, p=0.03). In the first minute of orthostasis MAP decreased more in patients than in healthy subjects (-4.0% versus -0.6%, p=0.04). MAP reached the pre-tilt values within 2 min in healthy subjects and 5 min in patients. Cerebral blood flow velocities fell to a similar degree and with similar time characteristics in patients and controls (-15.4% versus -16.7%, p=0.3). In both groups, patients and controls, changes of MAP did not correlate with changes of MBFV. It can be concluded that in IPD patients without symptoms of orthostatic dysregulation the autonomic circulatory control is impaired while the cerebral hemodynamic regulation during orthostasis is unaffected.