REM sleep without atonia and nocturnal body position in prediagnostic Parkinson's disease.

BACKGROUND: Sleep disturbances are features of Parkinson's disease (PD), that can already occur before PD diagnosis. The most investigated prodromal PD sleep disorder is REM sleep behavior disorder (RBD). The relation between other polysomnographic (PSG) alterations and the prediagnostic stages of PD, however, is less clear. METHODS: We performed a retrospective case-control study to characterize polysomnographic alterations in PD and prediagnostic PD. We included 63 PD subjects (33 subjects that underwent a video-PSG before PD diagnosis [13 with and 20 without RBD] and 30 subjects that underwent a PSG after PD diagnosis) and 30 controls. PSGs were analyzed for sleep stages, different RSWA variables, body position, arousals, periodic limb movements, and REM density. RESULTS: Higher subscores of all RSWA variables were observed in subjects with PD and prediagnostic PD (with and without RBD). Total RSWA, tonic RSWA and chin RSWA severity were significant predictors for all PD and prediagnostic PD groups. Our study also shows a higher percentage of nocturnal supine body position in all PD and prediagnostic PD groups. Supine body position percentage is the highest in the PD group and has a positive correlation with time since diagnosis. CONCLUSIONS: These findings suggest that increased total, tonic and chin RSWA as well as nocturnal supine body position are already present in prediagnostic PD, independently of RBD status. Prospective longitudinal studies are necessary to confirm the additional value of these PSG abnormalities as prodromal PD biomarkers.

REM sleep without atonia and the relation with Lewy body disease.

REM sleep without atonia (RSWA) is the polysomnographic finding of persistent muscle tone during REM sleep, resulting in paroxysmal phasic or tonic EMG activity. RSWA is essential for the diagnosis of REM sleep behavior disorder (RBD), but can also occur without dream-enacting behavior. Loss of atonia during REM sleep is considered as a biomarker for synucleinopathies. We will give an overview of the pathophysiology of RSWA and will highlight the diagnostic methods for RSWA. We will describe the different etiologies of RSWA and finally we will focus on the role of RSWA as biomarker for Lewy body disease. RSWA severity in isolated RBD patients is a potential predictor for early conversion to Parkinson's disease (PD) or dementia with Lewy bodies. In PD patients, RSWA severity is associated with more severe motor symptoms and disease progression. Future studies are needed to delineate the importance of isolated RSWA as prodromal marker of Lewy body disease.