Louis EK. Contemporary diagnostic visual and automated polysomnographic REM sleep without atonia thresholds in isolated REM sleep behavior disorder

STUDY OBJECTIVES

Accurate diagnosis of isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is crucial due to its injury potential and neurological prognosis. We aimed to analyze visual and automated REM sleep without atonia (RSWA) diagnostic thresholds applicable in varying clinical presentations in a contemporary cohort of patients with iRBD using submentalis (SM) and individual bilateral flexor digitorum superficialis (FDS) and anterior tibialis electromyography limb recordings during polysomnography.

METHODS

We analyzed RSWA in 20 patients with iRBD and 20 age-, REM-, apnea-hypopnea index-matched controls between 2017 and 2022 for phasic burst durations, density of phasic, tonic, and "any" muscle activity (number of 3-second mini-epochs containing phasic or tonic muscle activity divided by the total number of REM sleep 3-second mini-epochs), and automated Ferri REM atonia index (RAI). Group RSWA metrics were comparatively analyzed. Receiver operating characteristic curves determined optimized area under the curve (AUC) and maximized specificity and sensitivity diagnostic iRBD RSWA thresholds.

RESULTS

All mean RSWA metrics were higher in patients with iRBD than in controls (P < .05), except for selected anterior tibialis measures. Optimized, maximal specificity AUC diagnostic cutoffs for coprimary outcomes were: SM "any" 6.5%, 14.0% (AUC = 92.5%) and combined SM+FDS "any" 15.1%, 27.4% (AUC = 95.8%), while SM burst durations were 0.72, and 0.72 seconds (AUC 90.2%) and FDS RAI = 0.930, 0.888 (AUC 92.8%).

CONCLUSIONS

This study provides evidence for current quantitative RSWA diagnostic thresholds in chin and individual 4 limb muscles applicable in different iRBD clinical settings and confirms the key value of SM or SM+FDS to assure accurate iRBD diagnosis. Evolving iRBD recognition underscores the necessity of continuous assessment with future large, prospective, well-harmonized, multicenter polysomnographic analyses.

CITATION

Leclair-Visonneau L, Feemster JC, Bibi N, et al. Contemporary diagnostic visual and automated polysomnographic REM sleep without atonia thresholds in isolated REM sleep behavior disorder. J Clin Sleep Med. 2024;20(2):279-291.

Severity of REM sleep without atonia correlates with measures of cognitive impairment and depressive symptoms in REM sleep behaviour disorder

This study aimed to correlate REM sleep without atonia (RSWA) and neuropsychological data in patients with idiopathic/isolated REM sleep behaviour disorder (iRBD) and those with RBD associated with Parkinson's disease (PDRBD), in order to assess whether higher degrees of RSWA are related to poorer cognitive performance. A total of 142 subjects were enrolled: 48 with iRBD, 55 with PDRBD, and 39 PD without RBD (PDnoRBD). All participants underwent video-polysomnographic recording, clinical and neuropsychological assessment. RSWA was quantified according to two manual scoring methods (Montréal, SINBAR) and one automated (REM atonia index, RAI). Mild cognitive impairment (MCI) was diagnosed according to diagnostic criteria for MCI in Parkinson's disease. The relationship between neuropsychological scores and RSWA metrics was explored by multiple linear regression analysis and logistic regression models. Patients with iRBD showed significantly lower visuospatial functions and working memory, compared with the others. More severe RSWA was associated with a higher risk of reduced visuospatial abilities (OR 0.15), working memory (OR 2.48), attention (OR 2.53), and semantic fluency (OR 0.15) in the iRBD. In the whole group, a greater RSWA was associated with an increased risk for depressive symptoms (OR 3.6). A total of 57(40%) MCI subjects were found (17 iRBD, 26 PDRBD, and 14 PDnoRBD). Preserved REM-atonia was associated with a reduced odds of multi-domain MCI in the whole study population (OR 0.54). In conclusion, a greater severity of RSWA was associated with an increased risk for poor cognitive performance and depressive mood in patients with RBD. Moreover, higher RAI was associated with a lower risk of multi-domain MCI.

REM behavior disorder: When Parkinson's disease meets Morpheus

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by the absence of normal muscle atonia during REM sleep, resulting in excessive motor activity while dreaming. RBD can be classified as isolated which is the strongest clinical marker of prodromal synucleinopathy, or secondary, associated with other neurological diseases, mainly Parkinson's disease (PD) and dementia with Lewy bodies. The diagnosis of RBD must be systematically documented by a video polysomnography in the case of isolated RBD. PD associated with RBD may represent a distinct phenotype compared to PD without RBD, indicating a more severe and widespread synucleinopathy. Clinically, it is associated with poorer motor and cognitive performance, more severe non-motor symptoms, and faster disease progression. Imaging studies have revealed broader brain damage and significant alterations in cerebral metabolism and neurotransmission in PD patients with RBD. The management of RBD involves safety precautions and pharmacotherapy. Safety measures aim to minimize the risk of injury during RBD episodes and include creating a safe sleeping environment and separating the patient from their bed partner if necessary. Pharmacotherapy options include clonazepam and melatonin. Clonazepam must be cautiously prescribed in older patients due to potential side effects.

Quantification of REM sleep without atonia: A review of study methods and meta-analysis of their performance for the diagnosis of RBD

The present review focuses on REM sleep without atonia (RSWA) scoring methods. In consideration of the numerous papers published in the last decade, that used different methods for the quantification of RSWA, their systematic revision is an emerging need. We made a search using the PubMed, Embase, Scopus and Web of Science Databases, from 2010 until December 2021, combining the search term "RSWA" with "scoring methods", "IRBD", "alfasyn disease", and "neurodegenerative disease", and with each of the specific sleep disorders, diagnosed according to current criteria, with the identification of the references of interest for the topic. Furthermore, a Meta-analysis of the diagnostic performance of RSWA scoring methods, in terms of sensitivity and specificity, was carried out. The comparison of the hierarchical summary receiver-operating characteristic curves obtained for visual methods and that obtained for the automated REM sleep atonia index (RAI), shows substantially similar prediction areas indicating a comparable performance. This systematic review and meta-analysis support the validity of a series of visual methods and of the automated RAI in the quantification of RSWA with the purpose to guide clinicians in the interpretation of their results and their correct and efficient use within the diagnostic work-up for REM sleep behavior disorder.

Video-polysomnography procedures for diagnosis of rapid eye movement sleep behavior disorder (RBD) and the identification of its prodromal stages: guidelines from the International RBD Study Group

Video-polysomnography (v-PSG) is essential for diagnosing rapid eye movement (REM) sleep behavior disorder (RBD). Although there are current American Academy of Sleep Medicine standards to diagnose RBD, several aspects need to be addressed to achieve harmonization across sleep centers. Prodromal RBD is a stage in which symptoms and signs of evolving RBD are present, but do not yet meet established diagnostic criteria for RBD. However, the boundary between prodromal and definite RBD is still unclear. As a common effort of the Neurophysiology Working Group of the International RBD Study Group, this manuscript addresses the need for comprehensive and unambiguous v-PSG recommendations to diagnose RBD and identify prodromal RBD. These include: (1) standardized v-PSG technical settings; (2) specific considerations for REM sleep scoring; (3) harmonized methods for scoring REM sleep without atonia; (4) consistent methods to analyze video and audio recorded during v-PSGs and to classify movements and vocalizations; (5) clear v-PSG guidelines to diagnose RBD and identify prodromal RBD. Each section follows a common template: The current recommendations and methods are presented, their limitations are outlined, and new recommendations are described. Finally, future directions are presented. These v-PSG recommendations are intended for both practicing clinicians and researchers. Classification and quantification of motor events, RBD episodes, and vocalizations are however intended for research purposes only. These v-PSG guidelines will allow collection of homogeneous data, providing objective v-PSG measures and making future harmonized multicentric studies and clinical trials possible.

Assessing REM Sleep Behaviour Disorder: From Machine Learning Classification to the Definition of a Continuous Dissociation Index

Objectives: Rapid Eye Movement Sleep Behaviour Disorder (RBD) is regarded as a prodrome of neurodegeneration, with a high conversion rate to α-synucleinopathies such as Parkinson's Disease (PD). The clinical diagnosis of RBD co-exists with evidence of REM Sleep Without Atonia (RSWA), a parasomnia that features loss of physiological muscular atonia during REM sleep. The objectives of this study are to implement an automatic detection of RSWA from polysomnographic traces, and to propose a continuous index (the Dissociation Index) to assess the level of dissociation between REM sleep stage and atonia. This is performed using Euclidean distance in proper vector spaces. Each subject is assigned a dissociation degree based on their distance from a reference, encompassing healthy subjects and clinically diagnosed RBD patients at the two extremes. Methods: Machine Learning models were employed to perform automatic identification of patients with RSWA through clinical polysomnographic scores, together with variables derived from electromyography. Proper distance metrics are proposed and tested to achieve a dissociation measure. Results: The method proved efficient in classifying RSWA vs. not-RSWA subjects, achieving an overall accuracy, sensitivity and precision of 87%, 93% and 87.5%, respectively. On its part, the Dissociation Index proved to be promising in measuring the impairment level of patients. Conclusions: The proposed method moves a step forward in the direction of automatically identifying REM sleep disorders and evaluating the impairment degree. We believe that this index may be correlated with the patients' neurodegeneration process; this assumption will undergo a robust clinical validation process involving healthy, RSWA, RBD and PD subjects.

Neurophysiological Aspects of REM Sleep Behavior Disorder (RBD): A Narrative Review

REM sleep without atonia (RSWA) is the polysomnographic (PSG) hallmark of rapid eye movement (REM) sleep behavior disorder (RBD), a feature essential for the diagnosis of this condition. Several additional neurophysiological aspects of this complex disorder have also recently been investigated in depth, which constitute the focus of this narrative review, together with RSWA. First, we describe the complex neural network underlying REM sleep and its muscle atonia, focusing on the disordered mechanisms leading to RSWA. RSWA is then described in terms of its polysomnographic features, and the methods (visual and automatic) currently available for its scoring and quantification are exposed and discussed. Subsequently, more recent and advanced neurophysiological features of RBD are described, such as electroencephalography during wakefulness and sleep, transcranial magnetic stimulation, and vestibular evoked myogenic potentials. The role of the assessment of neurophysiological features in the study of RBD is then carefully discussed, highlighting their usefulness and sensitivity in detecting neurodegeneration in the early or prodromal stages of RBD, as well as their relationship with other proposed biomarkers for the diagnosis, prognosis, and monitoring of this condition. Finally, a future research agenda is proposed to help clarify the many still unclear aspects of RBD.

Neurophysiological Aspects of REM Sleep Behavior Disorder (RBD): A Narrative Review

REM sleep without atonia (RSWA) is the polysomnographic (PSG) hallmark of rapid eye movement (REM) sleep behavior disorder (RBD), a feature essential for the diagnosis of this condition. Several additional neurophysiological aspects of this complex disorder have also recently been investigated in depth, which constitute the focus of this narrative review, together with RSWA. First, we describe the complex neural network underlying REM sleep and its muscle atonia, focusing on the disordered mechanisms leading to RSWA. RSWA is then described in terms of its polysomnographic features, and the methods (visual and automatic) currently available for its scoring and quantification are exposed and discussed. Subsequently, more recent and advanced neurophysiological features of RBD are described, such as electroencephalography during wakefulness and sleep, transcranial magnetic stimulation, and vestibular evoked myogenic potentials. The role of the assessment of neurophysiological features in the study of RBD is then carefully discussed, highlighting their usefulness and sensitivity in detecting neurodegeneration in the early or prodromal stages of RBD, as well as their relationship with other proposed biomarkers for the diagnosis, prognosis, and monitoring of this condition. Finally, a future research agenda is proposed to help clarify the many still unclear aspects of RBD.

Preoperative REM Sleep Behavior Disorder and Subthalamic Nucleus Deep Brain Stimulation Outcome in Parkinson Disease 1 Year After Surgery

BACKGROUND AND OBJECTIVES

To determine whether patients with Parkinson disease (PD) eligible for subthalamic nucleus deep brain stimulation (STN-DBS) with probable REM sleep behavior disorder (RBD) preoperatively could be more at risk of poorer motor, nonmotor, and quality of life outcomes 12 months after surgery compared to those without RBD.

METHODS

We analyzed the preoperative clinical profile of 448 patients with PD from a French multicentric prospective study (PREDISTIM) according to the presence or absence of probable RBD based on the RBD Single Question and RBD Screening Questionnaire. Among the 215 patients with PD with 12 months of follow-up after STN-DBS, we compared motor, cognitive, psycho-behavioral profile, and quality of life outcomes in patients with (pre-opRBD+) or without (pre-opRBD-) probable RBD preoperatively.

RESULTS

At preoperative evaluation, pre-opRBD+ patients were older (61 ± 7.2 vs 59.5 ± 7.7 years; p = 0.02), had less motor impairment (Movement Disorder Society-sponsored version of the Unified Parkinson's Disease Rating Scale [MDS-UPDRS] III "off": 38.7 ± 16.2 vs 43.4 ± 7.1; p = 0.03) but more nonmotor symptoms on daily living activities (MDS-UPDRS I: 12.6 ± 5.5 vs 10.7 ± 5.3; p < 0.001), had more psychobehavioral manifestations (Ardouin Scale of Behavior in Parkinson's Disease total: 7.7 ± 5.1 vs 5.1 ± 0.4; p = 0.003), and had worse quality of life (Parkinson's Disease Questionnaire-39: 33 ± 12 vs 29 ± 12; p = 0.03), as compared to pre-opRBD- patients. Both pre-opRBD+ and pre-opRBD- patients had significant MDS-UPDRS IV score decrease (-37% and -33%, respectively), MDS-UPDRS III "med 'off'/stim 'on'" score decrease (-52% and -54%), and dopaminergic treatment decrease (-52% and -49%) after surgery, with no between-group difference. There was no between-group difference for cognitive and global quality of life outcomes.

CONCLUSIONS

In patients with PD eligible for STN-DBS, the presence of probable RBD preoperatively is not associated with a different clinical outcome 1 year after neurosurgery.

TRIAL REGISTRATION INFORMATION

NCT02360683.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in patients with PD eligible for STN-DBS, the presence of probable RBD preoperatively is not associated with poorer outcomes 1 year post surgery.

White matter changes in drug-naïve Parkinson's disease patients with impulse control & probable REM sleep behavior disorders

BACKGROUND

According to epidemiological studies, Parkinson's disease (PD) patients with probable REM sleep behavior disorder (pRBD) are more prone to develop impulse control disorders (ICDs), which is shown to be present in drug-naïve PD patients, and vice versa.

OBJECTIVES

To investigate white-matter integrity differences, with and without comorbid pRBD and ICDs.

METHODS

149 de-novo PD patients and 30 age- and gender-matched controls from the Parkinson's Progression Markers Initiative were studied. PD subjects were categorized into four groups with and without these comorbidities. We investigated the white matter integrity differences between these groups.

RESULTS

PDs with only ICDs manifested greater fractional anisotropy (FA) and lower mean diffusivity (MD) in ipsilateral cerebellar connections when compared to controls and to Parkinson's with both comorbid disorders. In contrast, significantly lower FA and higher MD in the ipsilateral fornix-stria-terminalis was observed in PDs with only pRBD compared to controls and to PDs without either comorbid disorder. Also, PDs with only pRBD manifested greater FA in contralateral putamen when compared to controls.

CONCLUSIONS

Our results suggest the presence of an underlying neural network in PDs with ICDs, particularly involving cerebellar connections, which makes the subjects susceptible to pRBD. Lower white-matter integrity in the fornix of PDs with only pRBD suggests a neuropathological pathway specific to sleep behavior disorder, independent of impulse control disorders. Greater white-matter integrity observed in PDs without comorbid ICDs, regardless of their comorbid pRBD status, might reflect compensatory mechanisms. Targeted therapies for this particular neuropathology may help prevent these comorbidities.

Biomarkers of conversion to α-synucleinopathy in isolated rapid-eye-movement sleep behaviour disorder

Patients with isolated rapid-eye-movement sleep behaviour disorder (RBD) are commonly regarded as being in the early stages of a progressive neurodegenerative disease involving α-synuclein pathology, such as Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy. Abnormal α-synuclein deposition occurs early in the neurodegenerative process across the central and peripheral nervous systems and might precede the appearance of motor symptoms and cognitive decline by several decades. These findings provide the rationale to develop reliable biomarkers that can better predict conversion to clinically manifest α-synucleinopathies. In addition, biomarkers of disease progression will be essential to monitor treatment response once disease-modifying therapies become available, and biomarkers of disease subtype will be essential to enable prediction of which subtype of α-synucleinopathy patients with isolated RBD might develop.

Associations between probable REM sleep behavior disorder, olfactory disturbance, and clinical symptoms in Parkinson's disease: A multicenter cross-sectional study

BACKGROUND

Rapid eye movement sleep behavior disorder (RBD) and olfactory dysfunction are useful for early diagnosis of Parkinson's disease (PD). RBD and severe olfactory dysfunction are also regarded as risk factors for cognitive impairment in PD. This study aimed to assess the associations between RBD, olfactory function, and clinical symptoms in patients with PD.

METHODS

The participants were 404 patients with non-demented PD. Probable RBD (pRBD) was determined using the Japanese version of the RBD screening questionnaire (RBDSQ-J) and the RBD Single-Question Screen (RBD1Q). Olfactory function was evaluated using the odor identification test for Japanese. Clinical symptoms were evaluated using the Movement Disorder Society Revision of the Unified PD Rating Scale (MDS-UPDRS) parts I-IV.

RESULTS

In total, 134 (33.2%) patients indicated a history of pRBD as determined by the RBD1Q and 136 (33.7%) by the RBDSQ-J based on a cutoff value of 6 points. Moreover, 101 patients were diagnosed as pRBD by both questionnaires, 35 by the RBDSQ-J only, and 33 by the RBD1Q only. The MDS-UPDRS parts I-III scores were significantly higher and disease duration significantly longer in the pRBD group. pRBD was significantly associated with male gender and the MDS-UPDRS part I score. The olfactory identification function was significantly reduced in the pRBD group.

CONCLUSIONS

About 33% of the patients with PD had pRBD based on the questionnaires, and both motor and non-motor functions were significantly decreased in these patients. These results suggest that more extensive degeneration occurred in patients with non-demented PD with RBD.