Is There a Difference in Autonomic Dysfunction Between Multiple System Atrophy Subtypes?

Background Autonomic dysfunction forms the diagnostic cornerstone in MSA. Data are limited on autonomic dysfunction differences between the two subtypes, MSA-C and MSA-P. Objectives To assess autonomic dysfunction in MSA subtypes and Parkinson's disease (PD) and compare it to healthy controls. Methods We conducted a cross-sectional study. A validated questionnaire (Scales for Outcomes in Parkinson's Disease-Autonomic Dysfunction; SCOPA-AUT) was used for symptom screening. Cardiovascular autonomic testing included deep breathing (change in heart rate, E: I ratio), Valsalva ratio, diastolic blood pressure (BP) rise (hand grip, cold pressor), and postural (tilt, 30:15 ratio) tests. Disease severity was assessed by the Unified MSA Rating Scale (UMSARS), H & Y stage, and International Parkinson and Movement Disorder Society Unified Parkinson's Disease Rating scale part III. Results MSA-P (48 subjects; age, 63.6 +/- 9.7 years; UMSARS, 45.0 +/- 16.5), MSA-C (52 subjects; age, 58.0 +/- 8.1 years; UMSARS, 44.0 +/- 12.8), PD (50 subjects; age, 57.6 +/- 6.7 years), and healthy controls (50 subjects; age, 58.0 +/- 8.0 years) were enrolled. MSA patients had higher SCOPA-AUT scores in gastrointestinal, urinary, cardiovascular, and sexual domains than controls and in gastrointestinal, urinary, and cardiovascular domains compared to PD. The two MSA subtypes did not differ in autonomic dysfunction. Heart-rate change on tilt and deep breathing, and diastolic BP rise on cold pressor test, differed significantly between MSA and PD patients. Conclusions Autonomic dysfunction symptomatology and cardiovascular autonomic tests were similar between MSA-P and MSA-C patients. Autonomic symptoms were more prominent in MSA than PD. Emphasis on these domains may improve likelihood of accurate clinical diagnosis of MSA at earlier stages.