Objective: To characterise autonomic impairment in REM sleep behaviour disorders, and to investigate the pathophysiological link between autonomic impairment and REM sleep behaviour disorder

Background: Idiopathic REM sleep behaviour disorder (iRBD) is a parasomnia characterized by lack of muscle atonia during REM sleep. It is widely regarded as a prodrome to multiple ⍺- synucleinopathies such as Parkinson’s Disease (PD), Lewy Body Dementia (DLB) and Multisystem atrophy (MSA). Autonomic nervous system dysfunction is common in iRBD. ¹ Accurate characterization of autonomic impairment, and investigation of pathological link between autonomic dysfunction and iRBD may provide a better understanding of pathophysiology of ⍺-synucleinopathies and offer targets for disease modifying therapies in the prodromal phase.

Method: We performed a literature search of Medline database using keywords: ‘REM sleep behaviour disorder’, ‘Autonomic Nervous System Diseases’, ‘Dysautonomia’, yielding 209 articles published in in English from 2000 to 2022. 26 articles met inclusion criteria and were included in this study.

Results: Questionnaire studies found higher prevalence of gastrointestinal, urinary and cardiovascular autonomic dysfunction iRBD patients than healthy control, with gastrointestinal domain most affected. Cardiovascular, sudomotor, pupillomotor domain were further characterized using objective tests comparing iRBD patients to control. Studies found reduced heart rate variability (predominantly driven by parasympathetic dysfunction), cardiac adrenergic dysfunction on cardiac scintigraphy, and sympathetic adrenergic dysfunction using cardiac reflex testing. 2 studies identified post-ganglionic sympathetic sudomotor dysfunction and 2 studies reported impaired pupillary response using pupillometry. Previous pathological studies have attributed REM sleep behaviour disorder symptoms to ventral medullar, which be responsible for generation of autonomic dysfunction.

Conclusion: Previous small-sized studies have demonstrated prevalent but heterogeneous autonomic impairment in iRBD patients. Multiple domains of autonomic nervous system may be affected. Pathologies in ventral medullar may be the common pathway generating REM sleep behaviour disorder and autonomic dysfunction. More comprehensive, accurate yet accessible test batteries are required to better evaluate autonomic impairment in iRBD patients.

References: FERINI-STRAMBI, L., et al. 2014. Autonomic symptoms in idiopathic REM behavior disorder: a multicentre case-control study. J Neurol, 261, 1112-8

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MDS Abstracts - https://www.mdsabstracts.org/abstract/autonomic-nervous-system-dysfunction-in-idiopathic-rem-sleep-behaviour-disorder/