The Role of Electrochemical Skin Conductance as a Screening Test of Cardiovascular Autonomic Neuropathy in Patients with Parkinson’s Disease

Autonomic disorders have been recognized as an important non-motor feature in Parkinson’s disease (PD). However, there is a paucity of information on the presence and severity of cardiovascular autonomic neuropathy (CAN) among different motor phenotypes. The aims of this study were to examine the feasibility of electrochemical skin conductance (ESC) measured by Sudoscan as a screening service for CAN in patients with PD and investigate the severity of CAN among different motor phenotypes. Design: This was a cross-sectional observational study that enrolled 63 patients with PD. Patients were divided into three phenotypes, postural instability/gait difficulty (PIGD), tremor-dominant (TD), and akinetic-rigid (AR), according to their motor symptoms. Cardiovascular autonomic function was measured, and the presence and severity of CAN was determined according to the composite autonomic scoring scale (CASS). Functional scores were measured by the Hoehn and Yahr (HY) stage and the Unified Parkinson’s Disease Rating Scale (UPDRS). The median HY stage was 2.0 [1.5, 3.0]. Median UPDRS total score was 23.0 (17.5, 30.5), 10.0 (6.0, 11.0) and 14.0 (6.3, 23.8) in groups of PIGD, TD and AR, respectively ( p = 0.001). Mean CASS was 1.7 ± 1.3, 0.6 ± 0.4, and 1.8 ± 1.5 in groups of PIGD, TD and AR, respectively ( p = 0.204). Although the ESC was not strongly associated with the cardiovascular autonomic parameters, the CAN risk score provided by Sudoscan significantly correlated with parameters of cardiovascular autonomic function, including heart rate response to deep breathing (HR_DB), Valsalva ratio (VR), and baroreflex sensitivity (BRS). By receiver-operating characteristic (ROC) analysis, if a patient’s CAN risk score is higher than 33.5 (%), it is recommended to be aware of the presence of CAN even in PD patients who are asymptomatic. The area under ROC curve was 0.704. Based on our results, CAN risk score may be used for screening of CAN in patients with PD before resorting to the more sophisticated and specific, but ultimately more time-consuming, complete autonomic function testing.