Objective: This study was designed to evaluate autonomic functions in iRBD compared to PD and controls including longitudinal follow-up assessments to evaluate their potential to serve as biomarkers.

Background: Autonomic symptoms are well-known non-motor symptoms in alpha-synucleinopathies, especially in Multi System Atrophy (MSA) and moderate to late stages of Parkinson’s disease (PD). Nevertheless, autonomic disturbances already occur in early and even prodromal stages of the disease progress as in clinically isolated REM Sleep Behavior disorder (iRBD). Thus, autonomic symptoms may serve as markers of conversion of prodromal disease stages and / or progression marker to predict outcome in iRBD and PD.

Method: We included 26 iRBD patients (age 71±7, range 57-83; f 8: 18m) and matched PD patients (n =29, age 68±10, range 47-83; f 14: 17m, UPDRS total 31,9±12,8, H&Y 2,2±0,8) as well as 38 controls (age 67±9; range 46-78; f18: m20). Exclusion criteria for each of the autonomic tests were defined according to method requirements and comprised ophthalmological and other conditions interfering with measurements (e.g. glaucoma, polyneuropathy). Detailed evaluations were performed including clinical examination (Unified Parkinson’s Disease Rating Scale (UPDRS)), questionnaires on autonomic and sleep symptoms and objective measurements using Ocular coherence tomography (SD-OCT), Pupillary light reflex testing and galvanic skin response (SudoScan) at baseline and as follow-up after 2 years in the iRBD cohort.

Results: Subjective autonomic burden was significantly elevated in patients with iRBD (p<0.001) and PD (p<0.001) compared to controls. Pupillary light reflex findings showed significant differences between PD patients and controls as well as iRBD patients and controls (e.g., amplitude, relative amplitude). Sudoscan showed impaired galvanic skin response of the hands in PD patients compared to controls (p=0.020) without significant progress over 2 years follow-up in the iRBD cohort. OCT RNFL measures did not differ significantly between groups at baseline, but mean RNFL significantly decreased over time in the iRBD cohort (P=0.011).

Conclusion: Autonomic measures showed differences between iRBD and PD patients as well as controls with progress in some of the measures over time in our cohort. Further research is needed to further evaluate these potential markers in neurodegenerative diseases.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/autonomic-symptoms-as-biomarkers-in-rem-sleep-behavior-disorder-and-parkinsons-disease/