Forehead sympathetic skin responses in determining autonomic involvement in Parkinson’s disease

•Forehead sympathetic skin response was examined in comparison to extremity SSR to test the hypothesis that forehead SSR might be impaired sooner than extremity SSR in PD.•Forehead SSR was more sensitive than extremity SSR in determining autonomous nervous system dysfunction not only in the late but also in the early stage of PD patients.•With further supportive research, forehead SSR might be used as a simple diagnostic electrophysiological test in the early diagnosis of ANS dysfunction.

ObjectiveThe purpose of this study was to evaluate forehead sympathetic skin response (SSR) and demonstrate any differences with extremity SSR in determining autonomic nervous system (ANS) involvement in patients with Parkinson’s disease (PD).MethodsTwenty early stage, 20 advanced stage idiopathic PD patients and 20 healthy controls participated in this study. SSR of forehead, hands and feet, heart rate variability (HRV), orthostatic intolerance, QT intervals and dysautonomic symptoms were evaluated.ResultsAbsent forehead SSR was determined unilaterally in 4, bilaterally in 7 early stage patients, and unilaterally in 4, bilaterally in 8 advanced stage PD patients; there was significant difference between early and advanced stage PD and control groups in terms of the lack of SSR (p = 0.000). Absent extremity SSR was determined in at least 1 extremity of 3 advanced stage PD patients, and none of the early stage PD patients. No difference was noted in HRV at rest between early and advanced stage PD and control groups (p = 0.218); but HRV at deep breathing was lower in both early and advanced PD patients compared to controls (p = 0.014, p = 0.002, respectively).ConclusionForehead SSR is more sensitive in determining ANS dysfunction not only in late but also in early stage of PD.SignificanceWith further supportive research, forehead SSR might be used as a simple diagnostic electrophysiological test in the early diagnosis of ANS dysfunction enabling proper treatment and increasing the quality of life of PD patients.