Idiopathic REM sleep behaviour disorder and neurodegeneration - an update

Genome-wide association study of REM sleep behavior disorder identifies polygenic risk and brain expression effects

Rapid-eye movement (REM) sleep behavior disorder (RBD), enactment of dreams during REM sleep, is an early clinical symptom of alpha-synucleinopathies and defines a more severe subtype. The genetic background of RBD and its underlying mechanisms are not well understood. Here, we perform a genome-wide association study of RBD, identifying five RBD risk loci near SNCA, GBA, TMEM175, INPP5F, and SCARB2. Expression analyses highlight SNCA-AS1 and potentially SCARB2 differential expression in different brain regions in RBD, with SNCA-AS1 further supported by colocalization analyses. Polygenic risk score, pathway analysis, and genetic correlations provide further insights into RBD genetics, highlighting RBD as a unique alpha-synucleinopathy subpopulation that will allow future early intervention.

Neuropsychiatric, neuropsychological, and neuroimaging features in isolated REM sleep behavior disorder: The importance of MCI

BACKGROUND

Mild cognitive impairment (MCI) is frequently diagnosed in patients with isolated rapid eye movement (REM) sleep behavior disorder (iRBD), although the extent of MCI-associated neuropathology has not yet been quantified. The present study compared the differences in neuropsychiatric, neuropsychological, and neuroimaging markers of neurodegeneration in MCI-iRBD and iRBD patients with normal cognition.

METHODS

Sixty-one patients with iRBD were included in the study: 30 patients were included in the MCI subgroup (RBD-MCI) and 31 in the normal cognition subgroup (RBD-NC). Both groups underwent neuropsychiatric and neuropsychological assessments to evaluate psychopathological symptoms and neuropsychological functions. Brain [18F]FDG PET and 123I-FP-CIT-SPECT were performed to evaluate brain glucose metabolism and nigrostriatal dopaminergic function in convenient subgroups of patients, respectively.

RESULTS

Neuropsychological measures generally confirmed overall cognitive decline in patients with iRBD-MCI. Immediate long-term verbal memory and visuospatial functions, as well as attentional-executive impairment were evident in the MCI group compared to the NC group. Neuroimaging results indicated reduced brain glucose uptake in the bilateral posterior cingulate cortex and more evident nigrostriatal deafferentation in the RBD-MCI group. There were no differences in psychopathological symptoms between the two groups.

CONCLUSIONS

This study confirmed that iRBD patients with MCI had a more impaired cognitive status that those with NC. Moreover, the MCI subgroup presented reduced cerebral glucose consumption in brain areas critical for cognition, and a more severe deafferentation of the nigro-striatal regions, highlighting the importance of identifying iRBD patients with MCI for urgent neuroprotective trials.

Emerging insights between gut microbiome dysbiosis and Parkinson's disease: Pathogenic and clinical relevance

Parkinson's disease (PD) is a complicated neurodegenerative disease, of which gastrointestinal disturbance appears prior to motor symptoms. Numerous studies have shed light on the roles of gastrointestinal tract and its neural connection to brain in PD pathology. In the past decades, the fields of microbiology and neuroscience have become ever more entwined. The emergence of gut microbiome has been considered as one of the key regulators of gut-brain function. With the advent of multi-omics sequencing techniques, gut microbiome of PD patients has been shown unique characteristics. The resident gut microbiota can exert considerable effects in PD and there are suggestions of a link between gut microbiome dysbiosis and PD progression. In this review, we summarize the latest progresses of gut microbiome dysbiosis in PD pathogenesis, further highlight the clinical relevance of gut microbiota and its metabolites in both the non-motor and motor symptoms of PD. Furthermore, we draw attention to the complex interplay between gut microbiota and PD drugs, with the purpose of improving drug efficacy and prescription accordingly. Further studies at specific strain level and longitudinal prospective clinical trials using optimized methods are still needed for the development of diagnostic markers and novel therapeutic regimens for PD.

A postmortem study suggests a revision of the dual-hit hypothesis of Parkinson's disease

The dual-hit hypothesis of Parkinson's disease (PD) originally postulated that a neurotropic pathogen leads to formation of α-synuclein pathology in the olfactory bulb (OB) and dorsal motor nucleus of the vagus (DMV) and then invades the brain from these two entry points. Little work has been conducted to validate an important underlying premise for the dual-hit hypothesis, namely that the initial Lewy pathology does arise simultaneously in the OB and the enteric nervous system (ENS) plexuses and DMV at the earliest disease stage. We conducted a focused re-analysis of two postmortem datasets, which included large numbers of mild Lewy body disease (LBD) cases. We found that cases with α-synuclein pathology restricted to the peripheral autonomic nervous system and/or lower brainstem (early body-first LBD cases) very rarely had any OB pathology, suggesting that Lewy pathology commonly arises in the ENS without concomitant involvement of the OB. In contrast, cases with mild amygdala-predominant Lewy pathology (early brain-first LBD cases) nearly always showed OB pathology. This is compatible with the first pathology being triggered in the OB or amygdala followed by secondary spreading to connected structures, but without early involvement of the ENS or lower brainstem. These observations support that the pathologic process starts in either the olfactory bulb or the ENS, but rarely in the olfactory bulb and gut simultaneously. More studies on neuropathological datasets are warranted to reproduce these findings. The agreement between the revised single-hit hypothesis and the recently proposed brain-first vs. body-first model of LBD is discussed.

Tonic REM sleep muscle activity is the strongest predictor of phenoconversion risk to neurodegenerative disease in isolated REM sleep behaviour disorder

Previous studies have shown that rapid eye movement sleep without atonia during polysomnography can predict the risk of phenoconversion to neurodegenerative disease in patients with isolated rapid eye movement sleep behaviour disorder. Discrepancy remains with regards to the morphology of rapid eye movement sleep without atonia that best predicts phenoconversion risk. This study aimed to ascertain the predictive value of tonic, phasic and mixed rapid eye movement sleep without atonia in patients with isolated rapid eye movement sleep behaviour disorder, at time of diagnosis. Sixty-four patients with polysomnography-confirmed isolated rapid eye movement sleep behaviour disorder, including 19 who phenoconverted during follow-up, were identified from an existing database. Tonic, phasic, mixed and "any" rapid eye movement sleep without atonia activity from the mentalis, tibialis anterior and flexor digitorum superficialis muscles was analysed blind to status using the diagnostic polysomnography. Rapid eye movement sleep without atonia variables were compared between converters and non-converters. Rapid eye movement sleep without atonia cut-offs predicting phenoconversion were established using receiver-operating characteristic analysis. The mean follow-up duration was 5.50 ± 4.73 years. Phenoconverters (n = 19) had significantly higher amounts of tonic (22.2 ± 19.1%, p = 0.0014), mixed (18.1 ± 14.1%, p = 0.0074) and "any" (mentalis muscle; 58.7 ± 28.0%, p = 0.0009) and all muscles (68.0 ± 20.8%, p = 0.0049) rapid eye movement sleep without atonia at diagnosis than non-converters. Optimal rapid eye movement sleep without atonia cut-off values predicting phenoconversion were 5.8% for tonic (73.7% sensitivity; 75.6% specificity), 7.3% for mixed (68.4% sensitivity; 73.3% specificity) and 43.6% for "any" (mentalis muscle; 68.4% sensitivity; 80.0% specificity) activity. "Any" (mentalis muscle) rapid eye movement sleep without atonia had the highest area under the curve (0.809) followed by tonic (0.799). The percentage of tonic rapid eye movement sleep without atonia was the strongest biomarker of phenoconversion in this cohort of patients with isolated rapid eye movement sleep behaviour disorder.

Isolated dream‐enactment behaviours as a prodromal hallmark of rapid eye movement sleep behaviour disorder

Recurrent dream-enactment behaviours (DEB) and rapid eye movement (REM) sleep without atonia (RSWA) are two diagnostic hallmarks of REM sleep behaviour disorder (RBD), a specific prodrome of α-synucleinopathy. Whilst isolated RSWA (without DEB) was suggested as a prodrome of RBD, the implication of 'isolated' recurrent DEB remains under-investigated. In this cross-sectional study, we sought to investigate neurodegenerative markers amongst the first-degree relatives (FDRs, aged >40 years) of patients with RBD who underwent clinical assessment for DEB, neurodegenerative markers, and video-polysomnography assessment. Isolated recurrent DEB was defined as: (i) three or more episodes of DEB, (ii) had a DEB episode in the past 1 year, and (iii) subthreshold RSWA. We identified 29 FDRs (mean [SD] age 53.4 [8.3] years, 55.2% male) with isolated recurrent DEB and 98 age and sex-matched FDRs as controls. Isolated DEB was associated with nightmare (27.6% versus 11.2%, p = 0.02), and the DEB group had a higher rate of current smoking (27.6% versus 3.1%, p = 0.006), type 2 diabetes mellitus (24.1% versus 10.2%, p = 0.003), anxiety disorder (24.1% versus 11.2%, p = 0.02), and constipation (hard lump of stool, 31.0% versus 7.1%, p < 0.001) than the control group. The present findings revealed that family relatives of patients with RBD with isolated recurrent DEB have increased risk of RBD and neurodegenerative features, which adds to the emerging data that isolated DEB is a prodromal feature of RBD and α-synucleinopathy neurodegeneration.

A Machine Learning Approach for Detecting Idiopathic REM Sleep Behavior Disorder

Background and purpose: Growing evidence suggests that Machine Learning (ML) models can assist the diagnosis of neurological disorders. However, little is known about the potential application of ML in diagnosing idiopathic REM sleep behavior disorder (iRBD), a parasomnia characterized by a high risk of phenoconversion to synucleinopathies. This study aimed to develop a model using ML algorithms to identify iRBD patients and test its accuracy. Methods: Data were acquired from 32 participants (20 iRBD patients and 12 controls). All subjects underwent a video-polysomnography. In all subjects, we measured the components of heart rate variability (HRV) during 24 h recordings and calculated night-to-day ratios (cardiac autonomic indices). Discriminating performances of single HRV features were assessed. ML models based on Logistic Regression (LR), Random Forest (RF) and eXtreme Gradient Boosting (XGBoost) were trained on HRV data. The utility of HRV features and ML models for detecting iRBD was evaluated by area under the ROC curve (AUC), sensitivity, specificity and accuracy corresponding to optimal models. Results: Cardiac autonomic indices had low performances (accuracy 63-69%) in distinguishing iRBD from control subjects. By contrast, the RF model performed the best, with excellent accuracy (94%), sensitivity (95%) and specificity (92%), while XGBoost showed accuracy (91%), specificity (83%) and sensitivity (95%). The mean triangular index during wake (TIw) was the best discriminating feature between iRBD and HC, with 81% accuracy, reaching 84% accuracy when combined with VLF power during sleep using an LR model. Conclusions: Our findings demonstrated that ML algorithms can accurately identify iRBD patients. Our model could be used in clinical practice to facilitate the early detection of this form of RBD.

Sleep-related hallucinations in patients with Parkinson's disease

Given that sleep-wake cycle dysfunction can cause hallucinations in Parkinson's disease patients, sleep-related hallucinations may be a different subtype from hallucinations that occur only during full wakefulness. However, few studies that distinguish the onset situations of hallucinations related to sleep from those that occur in full wakefulness have been conducted to investigate hallucinations in Parkinson's disease patients. Therefore, we conducted a multicenter observational study to investigate the prevalence of and factors associated with sleep-related hallucinations in patients with Parkinson's disease. Information on hallucinations was collected by using a questionnaire and face-to-face interviews. Of 100 consecutive patients with Parkinson's disease, 29 (29%) reported sleep-related hallucinations, and 16 (16%) reported hallucinations only in the full wakefulness. A longer duration of Parkinson's disease treatment (OR 1.35, 95% CI 1.07 to 1.72), higher Beck Depression Inventory-II scores (OR 1.07; 95% CI 1.01 to 1.14), and higher rapid eye movement sleep behavior disorder scores (OR 5.60; 95% CI 1.54 to 20.38) were independent factors associated with the presence of sleep-related hallucinations in a multivariable analysis. Sleep-related hallucinations, but not daytime hallucinations, were associated with probable rapid eye movement sleep behavior disorder. Phenomenological discrimination between sleep-related hallucinations and daytime hallucinations is important for elucidating the full pathology in Parkinson's disease and the mechanisms underlying hallucinations.

Polysomnographic Predictors of Sleep, Motor, and Cognitive Dysfunction Progression in Parkinson's Disease

PURPOSE OF REVIEW

Sleep disturbances are an important nonmotor feature of Parkinson's disease (PD) that can cause polysomnographic (PSG) alterations. These alterations are already present in early PD and may be associated with a specific disease course. This systematic review describes the role of PSG variables as predictors of sleep dysfunction, motor and cognitive dysfunction progression in PD.

RECENT FINDINGS

Nineteen longitudinal cohort studies were included. Their main findings were that (1) REM sleep behavioral events, REM sleep without atonia (RSWA), and electroencephalography (EEG) changes (mainly microsleep instability) are predictors of the development of REM sleep behavior disorder (RBD); (2) RBD, RSWA, and lower slow-wave sleep energy predict motor progression; (3) RBD, EEG slowing, and sleep spindles changes are predictors of cognitive deterioration; and (4) OSA is associated with severe motor and cognitive symptoms at baseline, with inconsistent findings on the effect of continuous positive airway pressure (CPAP) therapy for these symptoms. The results of our systematic review support a role of the video-PSG in disease progression prediction in PD and its usefulness as a biomarker. However, future studies are needed to investigate whether treatment of these PSG abnormalities and sleep disturbances may have a neuroprotective effect on disease progression.

Deep Clinical Phenotyping of Parkinson's Disease: Towards a New Era of Research and Clinical Care

Despite recent advances in technology, clinical phenotyping of Parkinson's disease (PD) has remained relatively limited as current assessments are mainly based on empirical observation and subjective categorical judgment at the clinic. A lack of comprehensive, objective, and quantifiable clinical phenotyping data has hindered our capacity to diagnose, assess patients' conditions, discover pathogenesis, identify preclinical stages and clinical subtypes, and evaluate new therapies. Therefore, deep clinical phenotyping of PD patients is a necessary step towards understanding PD pathology and improving clinical care. In this review, we present a growing community consensus and perspective on how to clinically phenotype this disease, that is, to phenotype the entire course of disease progression by integrating capacity, performance, and perception approaches with state-of-the-art technology. We also explore the most studied aspects of PD deep clinical phenotypes, namely, bradykinesia, tremor, dyskinesia and motor fluctuation, gait impairment, speech impairment, and non-motor phenotypes.

Sleep Disturbances in Neurological Disease: A Target for Intervention

Sleep is a biological function required for neurological and general health, but a significant and under-recognized proportion of the population has disturbed sleep. Here, we briefly overview the biology of sleep, sleep requirements over the lifespan, and common sleep disorders. We then turn our attention to five neurological diseases that significantly contribute to global disease burden and neurology practice makeup: epilepsy, headache, ischemic stroke, Parkinson's disease, and Alzheimer's disease. For each disease, we review evidence that sleep disturbances contribute to disease risk and severity and discuss existing data that addressing sleep disturbances may have disease-modifying effects. We provide recommendations derived from the literature and existing clinical guidelines to facilitate the evaluation and management of sleep disturbances within the context of each neurological disease. Finally, we synthesize identified needs and commonalities into future directions for the field and practical sleep-related recommendations for physicians caring for patients at risk for or currently suffering from neurological disease.

Efficacy of idebenone in the Treatment of iRBD into Synucleinopathies (EITRS): rationale, design, and methodology of a randomized, double-blind, multi-center clinical study

Background

As the strongest prodromal marker of α-synuclein-specific neurodegeneration, idiopathic REM sleep behavior disorder (iRBD) is becoming a focus of interest in disease-modifying therapy. Idebenone has been widely portrayed as a potent antioxidant targeting mitochondrial dysfunction. Previous study has identified the effect of idebenone on Parkinson's disease with promising outcomes by regulating mitophagy. A novel indication of idebenone should be highlighted in iRBD population.

Methods

The EITRS study is a randomized, double-blind, multi-center clinical study assessing the efficacy and safety of idebenone in the treatment of iRBD into synucleinopathies. One hundred forty-two patients (aged 40-75 years old) with clinically diagnosed iRBD are planned to be recruited with 80% statistical power and randomly assigned to idebenone (30 mg each time, three times a day) or matching placebo orally for 5 years. The assessment of rating scales, blood testing and neuroimaging examinations will be conducted at baseline, the 1st, 3rd and 5th year of follow-up. The primary efficacy endpoint is the 5-year conversion rate in patients with iRBD. The secondary endpoint is the safety and tolerability of idebenone in the treatment of iRBD. The study has been launched in July 2020.

Discussion

This is the first prospective study designed to identify the efficacy and safety of idebenone on the treatment of iRBD into synucleinopathies. The current results are expected to promote the development of evidence-based recommendations for the management of patients with iRBD. Furthermore, we hope to provide insights on a possible disease-modifying approach with robust evidence.

Trial Registration

Clinicaltrials.gov, identifier: NCT04534023.

Research trends and frontiers in exercise for movement disorders: A bibliometric analysis of global research from 2010 to 2021

Objective

To conduct a bibliometric analysis of trends and frontiers on exercise-based non-pharmacological treatments for movement disorders published between 2010 and 2021.

Methods

The Web of Science (WOS) Core Collection database was searched for articles published between 2010 and 2021. The CiteSpace software was used for in-depth analysis of the countries, institutions, journals, and collaboration networks among authors and their types of articles, developmental directions, references, and hot keywords of published articles.

Results

A total of 2,626 published articles were retrieved by search formula and included in the analysis. The number of publications fluctuated during this period, with 96 countries, 3,058 institutions, and 886 academic journals having published articles in this area, with subject classifications that focused on Clinical Neurology and Neurosciences. The United States has maintained its dominant and most influential position in exercise-based non-pharmacological research on movement disorders. Among research institutions and journals, the League of European Research Universities and Movement Disorders journals published the highest number of academic articles. In the last five years, the hot research topics by burst keyword analysis, are focused on treatments, research advances, and clinical treatments.

Conclusion

Research on exercise-based non-pharmacological treatments for movement disorders is generally on the rise from 2010 to 2021. The bibliometric analysis of this area will help provide potential collaborations among researchers, frontiers, and directions for development.

Prevalence and correlates of REM sleep behaviour disorder in patients with major depressive disorder: a two-phase study

OBJECTIVE

To investigate the prevalence and clinical correlates of video polysomnography (vPSG)-confirmed rapid eye movement sleep behaviour disorder (RBD) in patients with major depressive disorder (MDD).

METHODS

This is a clinic-based two-phase epidemiological study. In phase 1, patients with MDD were screened by a validated questionnaire, RBD Questionnaire-Hong Kong (RBDQ-HK). In phase 2, a subsample of both the screen-positive (RBDQ-HK >20) and screen-negative patients with MDD underwent further clinical and sleep assessment (vPSG) to confirm the diagnosis of RBD (MDD+RBD). Poststratification weighting method was used to estimate the prevalence of MDD+RBD. The total likelihood ratio and the probability of prodromal Parkinson's disease (PD) were calculated from prodromal markers and risk factors, as per the Movement Disorder Society research criteria.

RESULTS

A total of 455 patients with MDD were screened (median age (IQR)=52.66 (15.35) years, 77.58% woman, 43.74% positive). Eighty-one patients underwent vPSG and 12 of them were confirmed MDD+RBD. The prevalence of MDD+RBD was estimated to be 8.77% (95% CI: 4.33% to 16.93%), with possibly male predominance. MDD+RBD were associated with colour vision and olfaction deficit and a higher probability for prodromal PD.

CONCLUSIONS

Almost 9% of patients with MDD in the psychiatric outpatient clinic has vPSG-confirmed RBD. Comorbid MDD+RBD may represent a subtype of MDD with underlying α-synucleinopathy neurodegeneration. Systematic screening of RBD symptoms and necessity of vPSG confirmation should be highlighted for capturing this MDD subtype with a view to enhance personalised treatment and future neuroprotection to prevent neurodegeneration.

Association of Nucleus Basalis of Meynert Functional Connectivity and Cognition in Idiopathic Rapid-Eye-Movement Sleep Behavior Disorder

BACKGROUND AND PURPOSE

Cognitive impairments are common in isolated rapid-eye-movement sleep behavior disorder (iRBD), in which the cholinergic system may play an important role. This study aimed to characterize the cortical cholinergic activity using resting-state functional connectivity (FC) of the nucleus basalis of Meynert (NBM) according to the cognitive status of iRBD patients.

METHODS

In this cross-sectional study, 33 patients with polysomnography-confirmed iRBD and 20 controls underwent neuropsychological evaluations and resting-state functional magnetic resonance imaging. Thirteen of the iRBD patients had mild cognitive impairment (iRBD-MCI), and the others were age-matched patients with normal cognition (iRBD-NC). The seed-to-voxel NBM-cortical FC was compared among the patients with iRBD-MCI, patients with iRBD-NC, and controls. Correlations between average values of significant clusters and cognitive function scores were calculated in the patients with iRBD.

RESULTS

There were group differences in the FC of the NBM with the left lateral occipital cortex and lingual gyrus (adjusted for age, sex, and education level). The strength of FC was lower in the iRBD-MCI group than in the iRBD-NC and control groups (each post-hoc p<0.001). The average NBM-lateral occipital cortex FC was positively correlated with the memory-domain score in iRBD patients.

CONCLUSIONS

The results obtained in this study support that cortical cholinergic activity is impaired in iRBD patients with MCI. FC between NBM and posterior regions may play a central role in the cognitive function of these patients.

Metabolic connectivity of resting-state networks in alpha synucleinopathies, from prodromal to dementia phase

Previous evidence suggests that the derangement of large-scale brain networks reflects structural, molecular, and functional mechanisms underlying neurodegenerative diseases. Although the alterations of multiple large-scale brain networks in Parkinson’s disease (PD) and Dementia with Lewy Bodies (DLB) are reported, a comprehensive study on connectivity reconfiguration starting from the preclinical phase is still lacking. We aimed to investigate shared and disease-specific changes in the large-scale networks across the Lewy Bodies (LB) disorders spectrum using a brain metabolic connectivity approach. We included 30 patients with isolated REM sleep behavior disorder (iRBD), 28 with stable PD, 30 with DLB, and 30 healthy controls for comparison. We applied seed-based interregional correlation analyses (IRCA) to evaluate the metabolic connectivity in the large-scale resting-state networks, as assessed by [18F]FDG-PET, in each clinical group compared to controls. We assessed metabolic connectivity changes by applying the IRCA and specific connectivity metrics, such as the weighted and unweighted Dice similarity coefficients (DC), for the topographical similarities. All the investigated large-scale brain resting-state networks showed metabolic connectivity alterations, supporting the widespread involvement of brain connectivity within the alpha-synuclein spectrum. Connectivity alterations were already evident in iRBD, severely affecting the posterior default mode, attentive and limbic networks. Strong similarities emerged in iRBD and DLB that showed comparable connectivity alterations in most large-scale networks, particularly in the posterior default mode and attentive networks. Contrarily, PD showed the main connectivity alterations limited to motor and somatosensory networks. The present findings reveal that metabolic connectivity alterations in the large-scale networks are already present in the early iRBD phase, resembling the DLB metabolic connectivity changes. This suggests and confirms iRBD as a risk condition for progression to the severe LB disease phenotype. Of note, the neurobiology of stable PD supports its more benign phenotype.

Rapid eye movement sleep behaviour disorder: Past, present, and future

This manuscript presents an overview of REM sleep behaviour disorder (RBD) with a special focus on European contributions. After an introduction examining the history of the disorder, we address the pathophysiological and clinical aspects, as well as the diagnostic issues. Further, implications of RBD diagnosis and biomarkers are discussed. Contributions of European researchers to this field are highlighted.

[Cognitive disorders and sleep disturbances in long COVID]

BACKGROUND

During the last 2 years of the coronavirus disease 2019 (COVID-19) pandemic, knowledge about the long-term effects of the disease, the so-called long COVID, has rapidly grown; however, many questions remain unanswered, especially regarding the causes of persistent symptoms and their prognosis. Cognitive disorders and sleep disturbances are among the most frequent complaints. Both are associated with severe suffering and significant impairment in everyday functioning.

OBJECTIVE

What is known about the occurrence of cognitive disorders and sleep disturbances in long COVID? What are the influencing factors and what is known about the course over time and possible underlying mechanisms? What treatment options are available?

MATERIAL AND METHOD

In a narrative review, the most important findings on cognitive disorders and sleep disturbances in long COVID are presented. An overview of cohort studies with data on the prevalence and influencing factors of both symptom complexes is given. Current knowledge and hypotheses on pathophysiological mechanisms are presented and an outlook on treatment approaches is given.

RESULTS

About one in five of those affected report cognitive impairment more than 3 months after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and about one third report sleep disturbances. The latter comprise symptoms of insomnia as well as hypersomnia. Cognitive impairment and sleep disturbances occur in patients with all levels of initial disease severity. There are indications of an improvement of cognitive deficits over time but further longitudinal studies are needed.

CONCLUSION

In addition to the prognosis, the underlying disease mechanisms are still insufficiently understood. Furthermore, there is a great need for research on the efficacy and specific effective factors of therapeutic interventions.

Linguistic Abnormalities in Isolated Rapid Eye Movement Sleep Behavior Disorder

BACKGROUND

Patients with synucleinopathies frequently display language abnormalities. However, whether patients with isolated rapid eye movement sleep behavior disorder (iRBD) have prodromal language impairment remains unknown.

OBJECTIVE

We examined whether the linguistic abnormalities in iRBD can serve as potential biomarkers for conversion to synucleinopathy, including the possible effect of mild cognitive impairment (MCI), speaking task, and automation of analysis procedure.

METHODS

We enrolled 139 Czech native participants, including 40 iRBD without MCI and 14 iRBD with MCI, compared with 40 PD without MCI, 15 PD with MCI, and 30 healthy control subjects. Spontaneous discourse and story-tale narrative were transcribed and linguistically annotated. A quantitative analysis was performed computing three linguistic features. Human annotations were compared with fully automated annotations.

RESULTS

Compared with control subjects, patients with iRBD showed poorer content density, reflecting the reduction of content words and modifiers. Both PD and iRBD subgroups with MCI manifested less occurrence of unique words and a higher number of n-grams repetitions, indicating poorer lexical richness. The spontaneous discourse task demonstrated language impairment in iRBD without MCI with an area under the curve of 0.72, while the story-tale narrative task better reflected the presence of MCI, discriminating both PD and iRBD subgroups with MCI from control subjects with an area under the curve of up to 0.81. A strong correlation between manually and automatically computed results was achieved.

CONCLUSIONS

Linguistic features might provide a reliable automated method for detecting cognitive decline caused by prodromal neurodegeneration in subjects with iRBD, providing critical outcomes for future therapeutic trials. © 2022 International Parkinson and Movement Disorder Society.

What Is the Prognostic Significance of Rapid Eye Movement Sleep Without Atonia in a Polysomnogram?

SUMMARY

Freud said we are lucky to be paralyzed during sleep, so we cannot act out our dreams. Atonia of skeletal muscles normally present during rapid eye movement sleep prevents us from acting out our dreams. Observing rapid eye movement sleep without atonia in a polysomnogram in older adults first and foremost warrants consideration of rapid eye movement behavior disorder. Seventy-five to 90% of older adults with isolated rapid eye movement behavior disorder will develop a neurodegenerative disease within 15 years, most often a synucleinopathy. Rapid eye movement sleep without atonia in those younger than 50 years is commonly found in individuals with narcolepsy and those taking antidepressant medications.

End-to-end Deep Learning of Polysomnograms for Classification of REM Sleep Behavior Disorder

Rapid eye movement (REM) sleep behavior disorder (RBD) is parasomnia and a prodromal manifestation of Parkinson's disease. The current diagnostic method relies on manual scoring of polysomnograms (PSGs), a procedure that is time and effort intensive, subject to interscorer variability, and requires high level of expertise. Here, we present an automatic and interpretable diagnostic tool for RBD that analyzes PSGs using end-to-end deep neural networks. We optimized hierarchical attention networks in a 5-fold cross validation directly to classify RBD from PSG data recorded in 143 participants with RBD and 147 age-and sex-matched controls. An ensemble model using logistic regression was implemented to fuse decisions from networks trained in various signal combinations. We interpreted the networks using gradient SHAP that attribute relevance of input signals to model decisions. The ensemble model achieved a sensitivity of 91.4 % and a specificity of 86.3 %. Interpretation showed that electroencephalography (EEG) and leg electromyography (EMG) exhibited most patterns with high relevance. This study validates a robust diagnostic tool for RBD and proposes an interpretable and fully automatic framework for end-to-end modeling of other sleep disorders from PSG data. Clinical relevance- This study presents a novel diagnostic tool for RBD that considers neurophysiologic biomarkers in multiple modalities.

Isolated REM sleep behaviour disorder: current diagnostic procedures and emerging new technologies

Isolated REM sleep behaviour disorder (iRBD) is characterised by dream enactment behaviours, such as kicking and punching while asleep, and vivid/violent dreams. It is now acknowledged as a prodromal phase of neurodegenerative disease-approximately 80% of people with iRBD will develop dementia with Lewy Bodies, Parkinson's disease or another degenerative brain disease within 10 years. It is important that neurologists and other clinicians understand how to make an early accurate diagnosis of iRBD so that affected people can have the opportunity to take part in clinical trials. However, making a diagnosis can be clinically challenging due to a variety of reasons, including delayed referral, symptom overlap with other disorders, and uncertainty about how to confirm a diagnosis. Several methods of assessment are available, such as clinical interview, screening questionnaires and video polysomnography or 'sleep study'. This review aims to support clinical neurologists in assessing people who present with symptoms suggestive of iRBD. We describe the usefulness and limitations of each diagnostic method currently available in clinical practice, and present recent research on the utility of new wearable technologies to assist with iRBD diagnosis, which may offer a more practical assessment method for clinicians. This review highlights the importance of thorough clinical investigation when patients present with suspected iRBD and emphasises the need for easier access to diagnostic procedures for accurate and early diagnosis.

Clinical manifestation of patients with isolated rapid eye movement sleep behavior disorder after modest-to-long disease duration

Study Objectives

Patients with isolated rapid eye movement (REM) sleep behavior disorder (iRBD) are known to be at risk of neurodegenerative diseases but the time process of neurodegeneration remains unclear and its ethnic difference is rarely discussed. The objective of this study was to investigate the clinical manifestation of iRBD according to disease duration in a Korean cohort.

Methods

Patients who had been diagnosed with iRBD for at least 5 years were tracked and those currently remaining as iRBD were invited for motor, autonomic, olfactory, color discrimination, and cognitive tests. Cross-sectional comparison between patients with iRBD with modest disease duration (5–9.9 years) and long disease duration (≥10 years) was conducted.

Results

There were total of 198 patients with iRBD (135 males, 68.2%) tracked, whose average age at diagnosis was 65.9 years. Thirty-three had developed parkinsonism and 17 had developed dementia, resulting in a phenoconversion risk of 35.7% at 10 years. Hazard rate showed a gradually increasing trend over time, beginning from 2.1 conversions per year to 8.5 at 10 years. Patients with iRBD with a long disease duration (n = 19) had slightly higher motor scores than those with a modest duration (n = 82). However, they showed no difference in the frequency of motor abnormality or other clinical markers.

Conclusions

There is a possible racial or geographical difference of phenoconversion risk. The progression of neurodegeneration might be very subtle in that patients with iRBD with longer disease duration do not necessarily show higher frequency of neurodegeneration markers.

The relevance of synuclein autoantibodies as a biomarker for Parkinson's disease

Several studies have investigated if the levels of α-synuclein autoantibodies (α-syn AAb) differ in serum of Parkinson's disease (PD) patients and healthy subjects. Reproducible differences in their levels could serve as a biomarker for PD. The results of previous studies however remain inconclusive. With the largest sample size examined so far, we aimed to validate serum α-syn AAb levels as a biomarker for PD and investigated the presence of AAbs against other synucleins. We performed ELISA and immunoblots to determine synuclein AAb levels in the serum of 295 subjects comprising 157 PD patients from two independent cohorts, 46 healthy subjects, and 92 patients with other neurodegenerative disorders. Although serum α- and β-syn AAb levels were significantly reduced in patients with PD and other neurodegenerative disorders as compared to controls, the AAb levels displayed high inter-and intra-cohort variability. Furthermore, α-syn AAb levels showed no correlation to clinical parameters like age, disease duration, disease severity, and gender, that might also be directed against beta- and gamma-syn. In conclusion, serum synuclein AAb levels do allow the separation of PD from healthy subjects but not from other neurodegenerative disorders. Thus, synuclein AAbs cannot be regarded as a reliable biomarker for PD.

Association between probable REM sleep behavior disorder and increased dermal alpha-synuclein deposition in Parkinson's disease

INTRODUCTION

Many patients with Parkinson's disease suffer from REM sleep behavior disorder, potentially preceding the onset of motor symptoms. Phospho-alpha-synuclein is detectable in skin biopsies of patients with isolated REM sleep behavior disorder several years prior to the onset of manifest PD, but information on the association between dermal phospho-alpha-synuclein deposition and REM sleep behavior disorder in patients with manifest PD is limited. We therefore aimed to investigate the alpha-synuclein burden in dermal peripheral nerve fibers in patients with Parkinson's disease with and without REM sleep behavior disorder.

METHODS

Patients with Parkinson's disease (n = 43) who had undergone skin biopsy for the immunohistochemical detection of phosphorylated alpha-synuclein were screened for REM sleep behavior disorder using RBDSQ and Mayo Sleep Questionnaire. Skin biopsies from 43 patients with isolated polysomnography-confirmed REM sleep behavior disorder were used as comparators.

RESULTS

Dermal alpha-synuclein deposition was more frequently found (81.8% vs. 52.4%, p = 0.05) and was more abundant (p = 0.01) in patients with Parkinson's disease suffering from probable REM sleep behavior disorder compared to patients without REM sleep behavior disorder and was similar to patients with isolated REM sleep behavior disorder (79.1%).

CONCLUSION

The phenotype of REM sleep behavior disorder is associated with high amounts of dermal alpha-synuclein deposition, demonstrating a strong involvement of peripheral nerves in patients with this non-motor symptom and may argue in favor of REM sleep behavior disorder as an indicator of a "body-predominant" subtype of Parkinson's disease.

Brain atrophy in prodromal synucleinopathy is shaped by structural connectivity and gene expression

Isolated REM sleep behaviour disorder (iRBD) is a synucleinopathy characterized by abnormal behaviours and vocalizations during REM sleep. Most iRBD patients develop dementia with Lewy bodies, Parkinson's disease, or multiple system atrophy over time. Patients with iRBD exhibit brain atrophy patterns that are reminiscent of those observed in overt synucleinopathies. However, the mechanisms linking brain atrophy to the underlying alpha-synuclein pathophysiology are poorly understood. Our objective was to investigate how the prion-like and regional vulnerability hypotheses of alpha-synuclein might explain brain atrophy in iRBD. Using a multicentric cohort of 182 polysomnography-confirmed iRBD patients who underwent T1-weighted MRI, we performed vertex-based cortical surface and deformation-based morphometry analyses to quantify brain atrophy in patients (67.8 years, 84% men) and 261 healthy controls (66.2 years, 75%) and investigated the morphological correlates of motor and cognitive functioning in iRBD. Next, we applied the agent-based Susceptible-Infected-Removed model (i.e., a computational model that simulates in silico the spread of pathologic alpha-synuclein based on structural connectivity and gene expression) and tested if it recreated atrophy in iRBD by statistically comparing simulated regional brain atrophy to the atrophy observed in patients. The impact of SNCA and GBA gene expression and brain connectivity was then evaluated by comparing the model fit to the one obtained in null models where either gene expression or connectivity was randomized. The results showed that iRBD patients present with cortical thinning and tissue deformation, which correlated with motor and cognitive functioning. Next, we found that the computational model recreated cortical thinning (r = 0.51, p = 0.0007) and tissue deformation (r = 0.52, p = 0.0005) in patients, and that the connectome's architecture along with SNCA and GBA gene expression contributed to shaping atrophy in iRBD. We further demonstrated that the full agent-based model performed better than network measures or gene expression alone in recreating the atrophy pattern in iRBD. In summary, atrophy in iRBD is extensive, correlates with motor and cognitive function, and can be recreated using the dynamics of agent-based modelling, structural connectivity, and gene expression. These findings support the concepts that both prion-like spread and regional susceptibility account for the atrophy observed in prodromal synucleinopathies. Therefore, the agent-based Susceptible-Infected-Removed model may be a useful tool for testing hypotheses underlying neurodegenerative diseases and new therapies aimed at slowing or stopping the spread of alpha-synuclein pathology.

Relevance of sleep and associated structural changes in GBA1 mouse to human rapid eye movement behavior disorder

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a REM parasomnia that often predicts the later occurrence of alpha-synucleinopathies. Variants in the gene encoding for the lysosomal enzyme glucocerebrosidase, GBA, strongly increase the risk of RBD. In a GBA1-mouse model recently shown to mimic prodromal stages of α-synucleinopathy, we now demonstrate striking REM and NREM electroencephalographic sleep abnormalities accompanied by distinct structural changes in the more widespread sleep neurocircuitry.

Evolution of Prodromal REM Sleep Behavior Disorder to Neurodegeneration: A Retrospective, Longitudinal Case-control Study

BACKGROUND AND OBJECTIVES

Individuals with a history of recurrent dream-enactment behaviors, but with subthreshold REM sleep without atonia levels for REM sleep behavior disorder (RBD) diagnosis, are currently classified to have prodromal RBD (pRBD). However, the REM sleep elevated EMG diagnostic cut-off, progression trajectory, and long-term neurodegenerative outcome of pRBD are not well understood. This study aimed to delineate the evolution of REM sleep EMG levels, determine the EMG cut-off score for diagnosing pRBD, and examine the risk for neurodegenerative diseases of pRBD.

METHODS

This retrospective longitudinal case-control study recruited pRBD patients and age, sex, and follow-up duration matched controls who were free of neurodegenerative disease at baseline in the Sleep Assessment Unit, the Chinese University of Hong Kong from 1997 to 2018. Patients and controls underwent clinical and video-polysomnography assessments at baseline and follow-up(s). REM sleep EMG activity level on mentalis and anterior tibialis (AT) muscles on video-polysomnography at each visit was scored. The diagnosis of neurodegenerative diseases was confirmed by a neurologist.

RESULTS

44 patients (67.4 ± 8.2 years old, 6 females) and 44 controls were recruited. The combined REM sleep EMG level on mentalis and AT muscles of pRBD patients significantly increased during 8.2 ± 3.3 years of follow-up (from 19.3 ± 9.7% to 47.3 ± 27.4% with estimated annual increase of 3.9%), yielding 29 pRBD patients (66%) meeting the full-blown RBD diagnostic criteria. Baseline REM sleep mentalis and AT muscles EMG activity of patients who developed full-blown RBD could favourably differentiate pRBD from controls (6.3% for mentalis 'any' and 9.1% for combination of mentalis 'any' and bilateral AT muscles phasic EMG with AUC of 0.88 [0.78-0.98] and 0.97 [0.92-1.00] respectively). pRBD patients had a higher risk for neurodegenerative diseases (9 developed Parkinson's disease and 3 developed dementia with Lewy bodies) when compared to controls (5 developed Alzheimer's disease, adjusted hazard ratio = 2.95, 95% CI = 1.02-8.54).

CONCLUSIONS

pRBD has a predictive progression in both pathophysiology and neurodegenerative outcome. This finding has significant implications to the nosological status of pRBD, the current REM sleep-related EMG diagnostic criteria, spectrum concept of RBD and future neuroprotective intervention.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that EMG activity during REM sleep predicts the development of prodromal REM sleep behavior disorder.

Clinical outcome measures in dementia with Lewy bodies trials: critique and recommendations

The selection of appropriate outcome measures is fundamental to the design of any successful clinical trial. Although dementia with Lewy bodies (DLB) is one of the most common neurodegenerative conditions, assessment of therapeutic benefit in clinical trials often relies on tools developed for other conditions, such as Alzheimer's or Parkinson's disease. These may not be sufficiently valid or sensitive to treatment changes in DLB, decreasing their utility. In this review, we discuss the limitations and strengths of selected available tools used to measure DLB-associated outcomes in clinical trials and highlight the potential roles for more specific objective measures. We emphasize that the existing outcome measures require validation in the DLB population and that DLB-specific outcomes need to be developed. Finally, we highlight how the selection of outcome measures may vary between symptomatic and disease-modifying therapy trials.

Effective Treatment of Adult Parasomnias with Keishikaryukotsuboreito in Four Cases

Parasomnias are undesirable behaviors or experiences during sleep that manifest clinically as abnormal behavior, emotions, and nightmares. We herein report four elderly parasomnia patients who were successfully treated for abnormal nocturnal behaviors, including rapid eye movement (REM) sleep behavior disorders, with Keishikaryukotsuboreito (KRB), a Japanese traditional herbal medicine. KRB resolved nocturnal violent behaviors and sleep walking without any adverse effects. In one patient, occipital dominant spike-wave complexes induced by 3-Hz photic stimulation were reduced after KRB treatment, suggesting that KRB has inhibitory effects on brain irritability. KRB may represent a safe therapeutic option for treating parasomnias in the elderly.

Evolution patterns of probable REM sleep behavior disorder predicts Parkinson's disease progression

The course of REM sleep behavior disorder (RBD) variates in the early stage of Parkinson's disease. We aimed to delineate the association between the evolution pattern of probable RBD (pRBD) and the progression of Parkinson's disease (PD). 281 de novo PD patients from the Parkinson's Progression Markers Initiative database were included. Patients were followed up for a mean of 6.8 years and were classified into different groups according to the evolution patterns of pRBD. Disease progression was compared among groups using survival analysis, where the endpoint was defined as progression to Hoehn-Yahr stage 3 or higher for motor progression and progression to mild cognitive impairment for cognitive decline. At the 4th year of follow-up, four types of pRBD evolution patterns were identified: (1) non-RBD-stable (55.5%): patients persistently free of pRBD; (2) late-RBD (12.1%): patients developed pRBD during follow-up; (3) RBD-stable (24.9%): patients showed persistent pRBD, and (4) RBD-reversion (7.5%): patients showed pRBD at baseline which disappeared during follow-up. The RBD-reversion type showed the fastest motor progression while the RBD-stable type showed the fastest cognitive decline. At baseline, the RBD-reversion type showed the most severe gray matter atrophy in the middle frontal gyrus, while the RBD-stable type showed gray matter atrophy mainly in the para-hippocampal gyrus. Four types of early pRBD evolution patterns featured different brain lesions and predicted different courses of motor and cognitive decline in PD.

Toward Automated Articulation Rate Analysis via Connected Speech in Dysarthrias

PURPOSE

This study aimed to evaluate the reliability of different approaches for estimating the articulation rates in connected speech of Parkinsonian patients with different stages of neurodegeneration compared to healthy controls.

METHOD

Monologues and reading passages were obtained from 25 patients with idiopathic rapid eye movement sleep behavior disorder (iRBD), 25 de novo patients with Parkinson's disease (PD), 20 patients with multiple system atrophy (MSA), and 20 healthy controls. The recordings were subsequently evaluated using eight syllable localization algorithms, and their performances were compared to a manual transcript used as a reference.

RESULTS

The Google & Pyphen method, based on automatic speech recognition followed by hyphenation, outperformed the other approaches (automated vs. hand transcription: r > .87 for monologues and r > .91 for reading passages, p < .001) in precise feature estimates and resilience to dysarthric speech. The Praat script algorithm achieved sufficient robustness (automated vs. hand transcription: r > .65 for monologues and r > .78 for reading passages, p < .001). Compared to the control group, we detected a slow rate in patients with MSA and a tendency toward a slower rate in patients with iRBD, whereas the articulation rate was unchanged in patients with early untreated PD.

CONCLUSIONS

The state-of-the-art speech recognition tool provided the most precise articulation rate estimates. If speech recognizer is not accessible, the freely available Praat script based on simple intensity thresholding might still provide robust properties even in severe dysarthria. Automated articulation rate assessment may serve as a natural, inexpensive biomarker for monitoring disease severity and a differential diagnosis of Parkinsonism.

Possible predictors of phenoconversion in isolated REM sleep behaviour disorder: a systematic review and meta-analysis

BACKGROUND

A number of promising biomarkers for predicting imminent α-synucleinopathies have been suggested in isolated rapid eye movement sleep behaviour disorder (iRBD). However, existing evidence is conflicting without quantitative evaluation.

METHODS

PubMed, Web of Science and ClinicalTrials.gov were searched through June 2021 to identify possible predictors of phenoconversion from iRBD to Parkinson's disease (PD). The pooled HRs and standardised mean differences (SMDs) with 95% CIs were calculated using fixed-effects or random-effects model.

RESULTS

A total of 123 studies were included in the meta-analysis. Significant motor dysfunction (HR 1.83, 95% CI 1.33 to 2.51, I²=86.8%, p<0.001), constipation (HR 1.52, 95% CI 1.26 to 1.84, I²=8.3%, p=0.365), orthostatic hypotension (HR 1.93, 95% CI 1.05 to 3.53, I²=54.9%, p=0.084), hyposmia (HR 2.78, 95% CI 1.83 to 4.23, I²=23.9%, p=0.255), mild cognitive impairment (HR 2.27, 95% CI 1.58 to 3.27, I²=0%, p=0.681) and abnormal colour vision (SMD -0.34, 95% CI -0.63 to -0.05, I²=45.6%, p=0.087) correlated with susceptibility to PD. The process can also be traced by putaminal dopamine transporter imaging (HR 2.60, 95% CI 1.94 to 3.48, I²=0%, p=0.781) and tonic electromyographic activity (HR 1.50, 95% CI 1.04 to 2.15, I²=70%, p=0.018).

CONCLUSIONS

The predictive value of each biomarker was initially highlighted with comprehensive evaluation. Combining specific predictors with high sensitivity is promising for detecting phenoconversion in the prodromal stage. Large-scale and multicentre studies are pivotal to extend our findings.

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.

Real-Time Quaking- Induced Conversion Assays for Prion Diseases, Synucleinopathies, and Tauopathies

Prion diseases, synucleinopathies and tauopathies are neurodegenerative disorders characterized by deposition of abnormal protein aggregates in brain and other tissues. These aggregates consist of misfolded forms of prion, α-synuclein (αSyn), or tau proteins that cause neurodegeneration and represent hallmarks of these disorders. A main challenge in the management of these diseases is the accurate detection and differentiation of these abnormal proteins during the early stages of disease before the onset of severe clinical symptoms. Unfortunately, many clinical manifestations may occur only after neuronal damage is already advanced and definite diagnoses typically require post-mortem neuropathological analysis. Over the last decade, several methods have been developed to increase the sensitivity of prion detection with the aim of finding reliable assays for the accurate diagnosis of prion disorders. Among these, the real-time quaking-induced conversion (RT-QuIC) assay now provides a validated diagnostic tool for human patients, with positive results being accepted as an official criterion for a diagnosis of probable prion disease in multiple countries. In recent years, applications of this approach to the diagnosis of other prion-like disorders, such as synucleinopathies and tauopathies, have been developed. In this review, we summarize the current knowledge on the use of the RT-QuIC assays for human proteopathies.

SNCA rs3910105 Is Associated With Development of Rapid Eye Movement Sleep Behavior Disorder in Parkinson’s Disease

Background and Purpose

Rapid eye movement (REM) Rapid eye movement sleep behavior disorder (RBD) is a common non-motor symptom of PD. However, the association between the SNCA rs3910105 genotype and RBD in Parkinson’s disease (PD) remains unclear.

Methods

This study used Parkinson’s Progression Markers Initiative (PPMI) data and included 270 patients with newly diagnosed PD without RBD who were divided into SNCA rs3910105 C carriers (CC+CT; n = 187) and TT carriers (n = 83). They were followed up for 5 years to identify the development of RBD. To investigate the influence of cerebrospinal fluid (CSF) alpha-synuclein (α-syn) and β-amyloid 1–42 (Aβ₄₂) in the association between rs3910105 and RBD, the patients were additionally classified into “high-level” and “low-level” groups using cutoff values for CSF α-syn and Aβ₄₂ levels.

Results

At baseline, the rs3910105 C allele group had lower CSF α-syn and Aβ₄₂ levels than the TT group. During the 5.0-year follow-up, the rs3910105 C allele group had a higher incidence of RBD than the TT group. In the subgroup analyses, the effect of the rs3910105 C allele was not found in the “low-level” group. However, in the “high-level” group, the rs3910105 C allele independently increased the risk of RBD.

Conclusion

The SNCA rs3910105 C allele might be a novel genetic risk factor for RBD development in PD, α-syn pathways might have a role in this association and more basic research would be needed to elucidate the mechanism in the future.

Minor hallucinations in isolated rapid eye movement sleep behavior disorder indicative of early phenoconversion: A preliminary study

OBJECTIVES

Minor hallucinations (MH) are psychotic symptoms that can occur anywhere between prodromal to early Parkinson's disease and after onset of motor problems. MH include visual illusions, presence hallucinations, and passage hallucinations. Isolated rapid eye movement sleep behavior disorder (RBD) is a harbinger of neurodegenerative diseases. We conducted a retrospective cohort study to investigate the clinical characteristics of isolated RBD with MH and the risk of phenoconversion.

MATERIALS AND METHODS

We retrospectively analyzed the data of 36 patients with isolated RBD (four females; median age, 75.0 years). We defined cases reporting at least one minor hallucination as RBD with MH. Demographic data and cognitive function were compared between patients with and without MH, and Cox proportional hazards models estimated the risk of phenoconversion.

RESULTS

We included 10 (27.8%) patients with MH and 26 (72.2%) without MH. Patients with MH were older, had less dopamine transporter accumulation, more severe autonomic dysfunction, more depressive symptoms, and lower verbal fluency and symbol coding test scores than patients without MH. After follow-up (median, 2.50 years), 13.9% (5/36) of all patients developed phenoconversion (Parkinson's disease, two patients; dementia with Lewy bodies, three patients). The rate of phenoconversion was significantly higher in patients with MH (40.0% vs. 3.8%, p = .005). The Cox proportional hazards model adjusted for age, sex, and disease duration revealed that MH was a significant risk factor for phenoconversion (hazard ratio, 14.72; 95% confidence interval, 1.35-160.5).

CONCLUSIONS

Minor hallucinations may be utilized as early clinical markers for prodromal estimation of neurodegenerative diseases.

Cerebrospinal Fluid TNF-α and Orexin in Patients With Parkinson's Disease and Rapid Eye Movement Sleep Behavior Disorder

Background

Parkinson's disease (PD) pathological changes begin before motor symptoms appear. Rapid eye movement sleep behavior disorder (RBD) has the highest specificity and predictive value of any marker of prodromal PD. Tumor necrosis factor α (TNF-α) plays a part in the pathology of PD and disease conversion in isolated RBD (iRBD). TNF can also directly impair the hypocretin system in mice in vivo. As a result, we intend to investigate the effect of TNF-α on orexin levels in PD patients with RBD.

Method

Participants were recruited from the Department of Neurology of Xuanwu Hospital, Capital Medical University to engage in assessments on motor symptoms, sleep, cognition, etc. Then we collected blood and cerebrospinal fluid of all patients and 10 controls' cerebrospinal fluid. The levels of TNF-α in the serum and cerebrospinal fluid, as well as the level of orexin in the cerebrospinal fluid, were measured in the patients.

Results

The difference in TNF- levels in cerebrospinal fluid and serum between the three groups were not statistically significant. The levels of orexin in the three groups were not significantly lower than in the control group. UPDRS-III scores were significantly higher in the PD+RBD and PD-RBD groups than in the iRBD group. There was no statistically significant difference in H-Y stages, PSQI, or ESS scores between the PD+RBD and PD-RBD groups.

Conclusion

Our findings suggest that TNF-α may not have a significant effect on the orexinergic system in patients with Parkinson's disease and iRBD. As a result, it is necessary to investigate the changes in TNF-α and orexin levels in different disease stages and to enlarge the sample size to determine whether TNF-α affects the function of the orexin system, which may be related to the occurrence of RBD and disease progression in Parkinson's disease.

Melatonin Treatment for Sleep Disorders in Parkinson's Disease: A Meta-Analysis and Systematic Review

Objective

The efficacy of melatonin on sleep disorders in Parkinson's disease (PD) is still unclear. The purpose of this study was to investigate the efficacy of melatonin on sleep disorders in PD by summarizing evidence from randomized clinical trials (RCTs).

Methods

PubMed, Cochrane Library, EMBASE, and Web of Science databases were searched for studies published before 20 August 2021. Results were analyzed using Review Manager 5.2 software. We used Trial Sequential Analysis (TSA) software to avoid false-positive results caused by random errors.

Results

We included 7 studies in this systematic review and meta-analysis. The results of the meta-analysis showed that compared with placebo, the subjective sleep quality of patients with PD significantly improved after melatonin treatment (MD = −2.19, 95% CI: −3.53 to −0.86, P = 0.001). In the systematic review, we qualitatively analyzed the efficacy of melatonin on the objective sleep quality of patients with PD, and the results showed that melatonin exerted a positive effect with good safety and tolerability. However, there was no significant improvement in excessive daytime sleepiness assessed by the Epworth Sleepiness Scale (ESS).

Conclusion

We found that melatonin can significantly improve the subjective and objective sleep quality of patients with PD with good safety and tolerability. Melatonin could be considered an effective treatment for insomnia in patients with PD.

Impaired Ocular Tracking and Cortical Atrophy in Idiopathic Rapid Eye Movement Sleep Behavior Disorder

BACKGROUND

Idiopathic rapid eye movement sleep behavior disorder (iRBD) is a prodromal stage of synucleinopathies. Patients with synucleinopathies frequently display eye movement abnormalities. However, whether patients with iRBD have eye movement abnormalities remains unknown.

OBJECTIVE

The aim of this study was to assess eye movement abnormalities and related gray matter alterations and explore whether such abnormalities can serve as biomarkers to indicate phenoconversion to synucleinopathies in iRBD.

METHODS

Forty patients with iRBD with early disease progression and 35 healthy control subjects participated in a 15-minute ocular-tracking task that evaluated their control of eye movement abilities. They also underwent clinical assessments for olfactory function, nonmotor symptoms, and autonomic symptoms, all of which are biomarkers to predict phenoconversion to synucleinopathies in iRBD. A subgroup of the participants (20 patients with iRBD and 20 healthy control subjects) also participated in structural magnetic resonance imaging.

RESULTS

The ocular-tracking ability in patients with iRBD was inferior to that of healthy control subjects in two aspects: pursuit initiation and steady-state tracking. Cortical thinning in the right visual area V4 in patients with iRBD is coupled with impaired pursuit initiation. Furthermore, prolonged pursuit initiation in patients with iRBD exhibits a trend of correlation with olfactory loss, the earliest biomarker that develops prior to other prodromal biomarkers.

CONCLUSIONS

We found ocular-tracking abnormalities in patients with iRBD even early in their disease progression that have not been reported before. These abnormalities are coupled with atrophy of brain areas involved in the perception of object motion and might indicate phenoconversion to synucleinopathies in iRBD. © 2022 International Parkinson and Movement Disorder Society.

Magnetic Resonance Parkinsonism Index Is Associated with REM Sleep Behavior Disorder in Parkinson’s Disease

We investigated the association between the Magnetic Resonance Parkinsonism Index (MRPI) and REM sleep behavior disorder (RBD). We included 226 de novo PD patients (82 PD-RBD and 144 PD-noRBD) and 19 idiopathic RBD patients. Furthermore, 3T T1-weighted MR images were used for automated brainstem calculations. MRPI values were higher in the PD-RBD (p = 0.004) compared to PD-noRBD patients. Moreover, MRPI proved to be a significant predictor of REM Behavior Disorder Screening Questionnaire scores in PD (β = 0.195, p = 0.007) and iRBD patients (β = 0.582, p = 0.003). MRPI can be used as an imaging marker of RBD in patients with de novo PD and iRBD.

Passive Immunization in Alpha-Synuclein Preclinical Animal Models

Alpha-synucleinopathies include Parkinson’s disease, dementia with Lewy bodies, pure autonomic failure and multiple system atrophy. These are all progressive neurodegenerative diseases that are characterized by pathological misfolding and accumulation of the protein alpha-synuclein (αsyn) in neurons, axons or glial cells in the brain, but also in other organs. The abnormal accumulation and propagation of pathogenic αsyn across the autonomic connectome is associated with progressive loss of neurons in the brain and peripheral organs, resulting in motor and non-motor symptoms. To date, no cure is available for synucleinopathies, and therapy is limited to symptomatic treatment of motor and non-motor symptoms upon diagnosis. Recent advances using passive immunization that target different αsyn structures show great potential to block disease progression in rodent studies of synucleinopathies. However, passive immunotherapy in clinical trials has been proven safe but less effective than in preclinical conditions. Here we review current achievements of passive immunotherapy in animal models of synucleinopathies. Furthermore, we propose new research strategies to increase translational outcome in patient studies, (1) by using antibodies against immature conformations of pathogenic αsyn (monomers, post-translationally modified monomers, oligomers and protofibrils) and (2) by focusing treatment on body-first synucleinopathies where damage in the brain is still limited and effective immunization could potentially stop disease progression by blocking the spread of pathogenic αsyn from peripheral organs to the brain.

Sleep and circadian rhythms in Parkinson's disease and preclinical models

The use of animals as models of human physiology is, and has been for many years, an indispensable tool for understanding the mechanisms of human disease. In Parkinson's disease, various mouse models form the cornerstone of these investigations. Early models were developed to reflect the traditional histological features and motor symptoms of Parkinson's disease. However, it is important that models accurately encompass important facets of the disease to allow for comprehensive mechanistic understanding and translational significance. Circadian rhythm and sleep issues are tightly correlated to Parkinson's disease, and often arise prior to the presentation of typical motor deficits. It is essential that models used to understand Parkinson's disease reflect these dysfunctions in circadian rhythms and sleep, both to facilitate investigations into mechanistic interplay between sleep and disease, and to assist in the development of circadian rhythm-facing therapeutic treatments. This review describes the extent to which various genetically- and neurotoxically-induced murine models of Parkinson's reflect the sleep and circadian abnormalities of Parkinson's disease observed in the clinic.