Autonomic insufficiency in pupillary and cardiovascular systems in Parkinson’s disease

BackgroundIn Parkinson’s disease (PD), neurodegenerative changes have been observed in autonomic pathways involving multiple organ systems. We explore pupillary and cardiac autonomic measures as physiological manifestations of PD neurodegeneration.MethodsPupil measures (pupillary unrest (spontaneous changes of pupil diameter in darkness), constriction velocity and redilation velocity) were assessed in 35 participants (17 PD, 18 controls). Simultaneous cardiac measures (respiratory sinus arrythmia during deep breathing, Valsalva ratio, resting heart rate variability (HRV), orthostatic change in blood pressure and orthostatic change in heart rate) were obtained. Nonparametric statistics were used to compare PD with control participants and to calculate correlation coefficients between pupillary and cardiac measures.ResultsPupillary unrest and orthostatic decreases in systolic blood pressure were greater in PD than controls. Respiratory sinus arrythmia during deep breathing and resting HRV were lower in PD. Among all participants, there was a negative correlation between HRV and redilation velocity and a positive correlation between orthostatic change in heart rate and pupillary unrest. A modifying effect of PD was found on the association between high frequency HRV and pupillary unrest.ConclusionsResults demonstrate simultaneous autonomic dysfunction in both pupillary and cardiac systems in PD. The correlations between pupillary and cardiac measures suggest shared central centers of autonomic integration, while the modifying effect of PD may reflect autonomic effects of PD-related pathology not present in controls.