Cutaneous Sympathetic Vasoconstrictor Function in Multiple System Atrophy and Parkinson's Disease

Introduction: Autonomic disturbances are common features in Parkinson's disease (PD) and multiple system atrophy (MSA). Innervation of cutaneous vessels by vasoconstrictor neurons is an important pathway of the sympathetic nervous system. It is unclear to what extent this autonomic channel is involved in the two disorders. The aim of this study was to investigate the function of cutaneous sympathetic vasoconstrictor neurons in PD and MSA. To answer the question whether the investigation may be useful as a diagnostic test to distinguish between PD and MSA, the results were compared with the established head-up tilt testing. Methods: The study was performed on 34 patients with PD and on 15 patients with MSA. All patients underwent two different autonomic tests: 1) Head-up tilt-testing was applied as a marker for sympathetic muscle vasoconstrictor outflow. 2) Skin vasoconstrictor test was performed to investigate cutaneous sympathetic activity: Skin blood flow was measured with laser Doppler flowmetry during deep inspiratory gasps leading to a vasoconstriction due to activation of sympathetic vasoconstrictor neurones. Results: Orthostatic hypotension defined as a decrease in systolic blood pressure by 20mmHg or/and diastolic blood pressure of 10mmHg after 3 minutes of 70° head-up tilting was found in 58% of MSA and 38% of PD patients (p<0.02). A disturbed cutaneous sympathetic vasoconstriction in comparison to healthy controls was found in 62% of MSA and 32% of PD patients (p<0.02). Conclusions: The function of sympathetic skin vasoconstrictor neurons was disturbed in about 2/3 of MSA and about 1/3 of PD patients. These results were similar to autonomic failure detected by the head-up tilt testing. The skin vasoconstrictor-test seems to be useful to investigate involvement of cutaneous sympathetic outflow. Supported by the Deutsche Forschungsgemeinschaft (DFG Ba 1921/1–3).