REM sleep muscle activity in idiopathic REM sleep behavior disorder predicts phenoconversion

Abstract

ObjectiveTo determine whether REM sleep without atonia (RSWA) during polysomnography (PSG) predicts phenoconversion in patients with idiopathic REM sleep behavior disorder (iRBD), a prodromal feature of a neurodegenerative disease.MethodsWe analyzed RSWA in 60 patients with iRBD, including manual phasic, tonic, and any muscle activity in the submentalis and anterior tibialis muscles and the automated REM atonia index in the submentals. We identified patients who developed parkinsonism or mild cognitive impairment (MCI) during at least 3 years of follow-up after PSG. Kaplan-Meier analysis was performed and receiver operator curves were calculated to determine RSWA cutoffs predicting faster phenoconversion.ResultsTwenty-six (43%) patients developed parkinsonism (n = 17) or MCI (n = 9). Phenoconverters were older at iRBD diagnosis (p = 0.02). Median time to phenoconversion was 3.9 ± 2.5 years. iRBD phenoconverters had significantly more RSWA at diagnosis. Phenoconversion risk from iRBD diagnosis was 20% and 35% at 3 and 5 years, respectively, with greater risk in patients with iRBD with >46.4% any combined RSWA, which increased further to 30% and 55% at 3 and 5 years for patients >65 years of age at diagnosis.ConclusionsPatients with iRBD with higher amounts of polysomnographic RSWA had a greater risk of developing Parkinson disease or MCI. Patients with older age and higher RSWA amounts had more rapid phenoconversion than younger patients with RBD. Our study suggests that RSWA is a potential biomarker for risk stratification of iRBD phenoconversion that could facilitate prognostication for patients with iRBD.Classification of evidenceThis study provides Class II evidence that for patients with iRBD, increased RSWA correlates with increased risk for developing parkinsonism or MCI.

Residual Injurious Symptoms and Its Association With Neurodegenerative Outcomes in Idiopathic Rapid Eye Movement Sleep Behavior Disorder: A Retrospective, Longitudinal Follow‐up Study

“…In addition, despite with some variations of quantifying RSWA, several studies including our own data suggested that a baseline increase in RSWA, especially tonic activities, will predict future conversion to neurodegeneration, predominantly to PD. 13,26,27 Thus, it will be interesting to study further how the evolvement of RSWA, including both chin and limb EMG activities, will predict specific type of synucleinopathy. Furthermore, "leaving the bed" in patients with RBD was reported to be associated with the development of DLB or mild cognitive impairment in the Spanish cohort.…”

Timeline of Rapid Eye Movement Sleep Behavior Disorder in Overt Alpha‐Synucleinopathies

“…Accordingly, iRBD has been recognized as a prodromal feature of alpha‐synucleinopathies. The risk of phenoconversion from iRBD to an overt alpha‐synucleinopathy is ~7 to 8% per year, approaching 35% at 5 years, and between 41 and 91% risk after 6 to 15 years 9,10,14,16–20 . RBD might even identify a distinct phenotype of PD 21,22 …”

“…synucleinopathy is~7 to 8% per year, approaching 35% at 5 years, and between 41 and 91% risk after 6 to 15 years. 9,10,14,[16][17][18][19][20] RBD might even identify a distinct phenotype of PD. 21,22 Despite the large number of studies examining RBD as a risk factor or prodromal synucleinopathy, few studies have examined the life-long sequence of RBD, including both before and after the onset of synucleinopathies.…”

Automated Assessment of Quantitative REM Sleep without Atonia for Diagnosis of REM Sleep Behavior Disorder

“…phy [1], and recent studies have shown that the degree of REM sleep without atonia (RSWA) predicts alpha-synucleionpathies [2,3]. Therefore, early detection of RBD is becoming increasingly important.…”

“…According to recent reports, tonic and phasic RSWA have different clinical implications in RBD. It was suggested that phasic activity was related to the violent expressions of dream-enacting behaviors whereas tonic activity was more closely related to disease progression to synuceinopathies [3]. It is expected that different aspects of RBD could be analyzed by calculating and quantifying tonic and phasic respectively.…”