Clinical correlates of obstructive sleep apnoea in idiopathic normal pressure hydrocephalus

BACKGROUND AND PURPOSE

The pathogenesis of idiopathic normal pressure hydrocephalus (iNPH) remains controversial. Limited studies have indicated a high prevalence of obstructive sleep apnoea (OSA) amongst iNPH patients. The aim was to investigate the clinical correlates of OSA in iNPH patients.

METHODS

In this cross-sectional observational study, consecutive iNPH patients were prospectively enrolled. Evaluations included the iNPH Rating Scale, the Movement Disorder Society Unified Parkinson's Disease Rating Scale part III, the time and number of steps to walk 10 m, the Epworth Sleepiness Scale, the Pittsburgh Sleep Quality Index, a complete neuropsychological evaluation, 3-T brain MRI, full-night video-polysomnography, tap test and cerebrospinal fluid (CSF) neurodegeneration biomarkers.

RESULTS

Fifty-one patients were screened, of whom 38 met the inclusion criteria. Amongst the recruited patients, 19/38 (50%) exhibited OSA, with 12/19 (63.2%) presenting moderate to severe disorder. OSA+ iNPH patients required more time (p = 0.02) and more steps (p = 0.04) to complete the 10-m walking test, had lower scores on the gait subitem of the iNPH Rating Scale (p = 0.04) and demonstrated poorer performance on specific neuropsychological tests (Rey Auditory Verbal Learning Test immediate recall, p = 0.03, and Rey-Osterrieth Complex Figure, p = 0.01). Additionally, OSA+ iNPH patients had higher levels of total tau (p = 0.02) and phospho-tau (p = 0.03) in their CSF but no statistically significant differences in beta-amyloid (1-42) levels compared to OSA- iNPH patients.

CONCLUSION

Obstructive sleep apnoea is highly prevalent in iNPH patients, particularly at moderate to severe levels. OSA is associated with worse motor and cognitive performance in iNPH. The CSF neurodegeneration biomarker profile observed in OSA+ iNPH patients may reflect OSA-induced impairment of cerebral fluid dynamics.

Reading the mind in the eyes in patients with idiopathic REM sleep behavior disorder

OBJECTIVES

Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is characterized by vocalizations, jerks, and motor behaviors during REM sleep, often associated with REM-related dream content, which is considered a prodromal stage of α-synucleinopathy. The results of the Reading the Mind in the Eyes (RME) reflecting affective Theory of Mind (ToM) are inconsistent in α-synucleinopathy. The present study tried to investigate the RME in patients with iRBD.

METHODS

A total of 35 patients with iRBD and 26 healthy controls were included in the study. All participants were administered the RME and the cognitive assessments according to a standard procedure. The patients with iRBD were further divided into two groups (high or low RME) according to the scores of the RME (> 21, or ≤ 20).

RESULTS

The patients with iRBD had worse scores on cognitive tests compared with healthy controls involving global cognitive screening, memory, and visuospatial abilities (p < 0.05), but the scores of the RME were similar between the two groups (20.83 ± 3.38, 20.58 ± 3.43) (p ˃ 0.05). Patients with low RME had more obvious cognitive impairments than healthy controls. After applying Bonferroni correction for multiple tests, the low REM group only performed worse on the Sum of trials 1 to 5 and delayed recall of the RAVLT compared with the healthy control group (p < 0.001, = 0.002). The RME correlated with the scores of cognitive tests involving executive function, attention, memory, and visuospatial function.

CONCLUSIONS

The changes in RME had a relationship with cognitive impairments, especially memory, in patients with iRBD.

EEG-based machine learning models for the prediction of phenoconversion time and subtype in isolated rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

Isolated rapid eye movement sleep behavior disorder (iRBD) is a prodromal stage of α-synucleinopathies and eventually phenoconverts to overt neurodegenerative diseases including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). Associations of baseline resting-state electroencephalography (EEG) with phenoconversion have been reported. In this study, we aimed to develop machine learning models to predict phenoconversion time and subtype using baseline EEG features in patients with iRBD.

METHODS

At baseline, resting-state EEG and neurological assessments were performed on patients with iRBD. Calculated EEG features included spectral power, weighted phase lag index, and Shannon entropy. Three models were used for survival prediction, and four models were used for α-synucleinopathy subtype prediction. The models were externally validated using data from a different institution.

RESULTS

A total of 236 iRBD patients were followed up for up to 8 years (mean 3.5 years), and 31 patients converted to α-synucleinopathies (16 PD, 9 DLB, 6 MSA). The best model for survival prediction was the random survival forest model with an integrated Brier score of 0.114 and a concordance index of 0.775. The K-nearest neighbor model was the best model for subtype prediction with an area under the receiver operating characteristic curve of 0.901. Slowing of the EEG was an important feature for both models.

CONCLUSIONS

Machine learning models using baseline EEG features can be used to predict phenoconversion time and its subtype in patients with iRBD. Further research including large sample data from many countries is needed to make a more robust model.

Neuropsychological Changes in Isolated REM Sleep Behavior Disorder: A Systematic Review and Meta-analysis of Cross-sectional and Longitudinal Studies

The aim of this meta-analysis is twofold: (a) to assess cognitive impairments in isolated rapid eye movement (REM) sleep behavior disorder (iRBD) patients compared to healthy controls (HC); (b) to quantitatively estimate the risk of developing a neurodegenerative disease in iRBD patients according to baseline cognitive assessment. To address the first aim, cross-sectional studies including polysomnography-confirmed iRBD patients, HC, and reporting neuropsychological testing were included. To address the second aim, longitudinal studies including polysomnography-confirmed iRBD patients, reporting baseline neuropsychological testing for converted and still isolated patients separately were included. The literature search was conducted based on PRISMA guidelines and the protocol was registered at PROSPERO (CRD42021253427). Cross-sectional and longitudinal studies were searched from PubMed, Web of Science, Scopus, and Embase databases. Publication bias and statistical heterogeneity were assessed respectively by funnel plot asymmetry and using I2. Finally, a random-effect model was performed to pool the included studies. 75 cross-sectional (2,398 HC and 2,460 iRBD patients) and 11 longitudinal (495 iRBD patients) studies were selected. Cross-sectional studies showed that iRBD patients performed significantly worse in cognitive screening scores (random-effects (RE) model = -0.69), memory (RE model = -0.64), and executive function (RE model = -0.50) domains compared to HC. The survival analyses conducted for longitudinal studies revealed that lower executive function and language performance, as well as the presence of mild cognitive impairment (MCI), at baseline were associated with an increased risk of conversion at follow-up. Our study underlines the importance of a comprehensive neuropsychological assessment in the context of iRBD.

Prodromal dementia with Lewy bodies in REM sleep behavior disorder: A multicenter study

INTRODUCTION

Isolated/idiopathic rapid eye movement sleep behavior disorder (iRBD) is a powerful early predictor of dementia with Lewy bodies (DLB) and Parkinson's disease (PD). This provides an opportunity to directly observe the evolution of prodromal DLB and to identify which cognitive variables are the strongest predictors of evolving dementia.

METHODS

IRBD participants (n = 754) from 10 centers of the International RBD Study Group underwent annual neuropsychological assessment. Competing risk regression analysis determined optimal predictors of dementia. Linear mixed-effect models determined the annual progression of neuropsychological testing.

RESULTS

Reduced attention and executive function, particularly performance on the Trail Making Test Part B, were the strongest identifiers of early DLB. In phenoconverters, the onset of cognitive decline began up to 10 years prior to phenoconversion. Changes in verbal memory best differentiated between DLB and PD subtypes.

DISCUSSION

In iRBD, attention and executive dysfunction strongly predict dementia and begin declining several years prior to phenoconversion.

HIGHLIGHTS

Cognitive decline in iRBD begins up to 10 years prior to phenoconversion. Attention and executive dysfunction are the strongest predictors of dementia in iRBD. Decline in episodic memory best distinguished dementia-first from parkinsonism-first phenoconversion.

Cognitive and motor profiles as prodromal markers in predicting phenoconversion and phenotype in isolated REM sleep behavior disorder

OBJECTIVE

To determine the clinical markers based on cognitive and motor profiles in predicting phenoconverion and phenotype in isolated rapid eye movement sleep behavior disorder (iRBD).

METHODS

45 iRBD patients and 25 healthy controls were included in the follow-up study. All participates received comprehensive evaluations of cognitive, motor and autonomic function at baseline. Positive phenoconversion were identified according to standard diagnostic criteria during follow-up.

RESULTS

21 iRBD patients displayed phenoconversion in a mean follow-up of 2.9 ± 1.6 years, with 14 presenting motor phenotype and 7 cognitive phenotype. In iRBD, visuospatial, memory, attention-executive function, information processing speed, and motor function predicted phenoconversion, with the combination of Trail Making Test (TMT) and Alternate-tap Test (ATT) performing best (sensitivity = 95.0 %, specificity = 75.0 %); attention-executive function, information processing speed, and motor function predicted motor phenotype conversion, with the combination of TMT and ATT performing best (sensitivity = 100 %, specificity = 66.7 %); visuospatial, memory, and attention-executive function predicted cognitive phenotype conversion, with TMT performing best (sensitivity = 83.3 %, specificity = 91.7 %). Furthermore, individuals with lower z-scores of TMT, Symbol Digit Modalities Test, and ATT than the established cutoff values in iRBD exhibited a significantly higher risk for phenoconversion at follow-up (HR = 2.98, 9.53, 11.68; respectively).

CONCLUSIONS

In iRBD, the attention-executive and motor function served as optimum combined markers in predicting phenoconversion and motor phenotype, whereas the attention-executive function performed best in predicting cognitive phenotype. Poor attention-executive function, information processing speed and motor function in iRBD independently increased the risk of phenoconversion.

REM sleep behavior disorder: update on diagnosis and management

REM sleep behavior disorder (RBD) is characterized by a loss of atonia of skeletal muscles during REM sleep, associated with acting out behaviors during dreams. Knowledge of this pathology is important to predict neurodegenerative diseases since there is a strong association of RBD with diseases caused by the deposition of alpha-synuclein in neurons (synucleinopathies), such as Parkinson's disease (PD), multiple system atrophy (MSA), and dementia with Lewy bodies (DLB). Proper diagnosis of this condition will enable the use of future neuroprotective strategies before motor and cognitive symptoms. Diagnostic assessment should begin with a detailed clinical history with the patient and bed partner or roommate and the examination of any recorded home videos. Polysomnography (PSG) is necessary to verify the loss of sleep atonia and, when documented, the behaviors during sleep. Technical recommendations for PSG acquisition and analysis are defined in the AASM Manual for the scoring of sleep and associated events, and the PSG report should describe the percentage of REM sleep epochs that meet the criteria for RWA (REM without atonia) to better distinguish patients with and without RBD. Additionally, PSG helps rule out conditions that may mimic RBD, such as obstructive sleep apnea, non-REM sleep parasomnias, nocturnal epileptic seizures, periodic limb movements, and psychiatric disorders. Treatment of RBD involves guidance on protecting the environment and avoiding injuries to the patient and bed partner/roommate. Use of medications are also reviewed in the article. The development of neuroprotective medications will be crucial for future RBD therapy.

Neuropsychological evaluation of phenoconversion risk in REM sleep behaviour disorder: A scoping review

The objective of this study was to assess the role of cognitive evaluation in the prediction of phenoconversion in polysomnography-confirmed idiopathic or isolated rapid eye movement sleep behaviour disorder, through a scoping review focussing on a longitudinal comprehensive neuropsychological assessment of patients with idiopathic REM sleep behaviour disorder. A literature search (2006-2022) yielded 1034 records, and 20 were selected for analysis. The sample included 899 patients from eight different cohorts and five countries. We extracted data on clinical evolution, mild cognitive impairment diagnosis, neuropsychological tests used, and classification of cognitive domains. Tests, cognitive domains, and mild cognitive impairment definitions were heterogeneous across the studies, precluding a meta-analysis. Ten studies (50%) evaluated the presence of mild cognitive impairment; 14 studies (70%) grouped neuropsychological tests into between three (6 studies, 21.4%) and seven (1 study, 7.1%) cognitive domains. The most frequently used tests were semantic fluency, Stroop colour word test, trail making test A and B, digit span, Rey auditory verbal learning test, and Rey-Osterrieth figure. All except digit span showed a role in predicting phenoconversion. The authors did not consistently assign tests to specific cognitive domains. In conclusion, we discuss methodological differences between the studies and highlight the need for a standardised framework for neuropsychological data acquisition and presentation, based on a multilevel approach covering test selection, domain assignment, and mild cognitive impairment diagnostic criteria.

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.

Considering REM Sleep Behavior Disorder in the Management of Parkinson's Disease

Rapid eye movement (REM) sleep behavior disorder (RBD) is the result of the loss of physiological inhibition of muscle tone during REM sleep, characterized by dream-enacting behavior and widely recognized as a prodromal manifestation of alpha-synucleinopathies. Indeed, patients with isolated RBD (iRBD) have an extremely high estimated risk to develop a neurodegenerative disease after a long follow up. Nevertheless, in comparison with PD patients without RBD (PDnoRBD), the occurrence of RBD in the context of PD (PDRBD) seems to identify a unique, more malignant phenotype, characterized by a more severe burden of disease in terms of both motor and non-motor symptoms and increased risk for cognitive decline. However, while some medications (eg, melatonin, clonazepam, etc.) and non-pharmacological options have been found to have some therapeutic benefits on RBD there is no available treatment able to modify the disease course or, at least, slow down the neurodegenerative process underlying phenoconversion. In this scenario, the long prodromal phase may allow an early therapeutic window and, therefore, the identification of multimodal biomarkers of disease onset and progression is becoming increasingly crucial. To date, several clinical (motor, cognitive, olfactory, visual, and autonomic features) neurophysiological, neuroimaging, biological (biofluids or tissue biopsy), and genetic biomarkers have been identified and proposed, also in combination, as possible diagnostic or prognostic markers, along with a potential role for some of them as outcome measures and index of treatment response. In this review, we provide an insight into the present knowledge on both existing and future biomarkers of iRBD and highlight the difference with PDRBD and PDnoRBD, including currently available treatment options.

Influence of RBD onset on the clinical characteristics of Parkinson's disease patients: a retrospective study

INTRODUCTION

In Parkinson's disease (PD), rapid eye movement (REM) sleep behavior disorder (RBD) might either precede the appearance of motor symptoms, or develop during the disease course. PD patients with RBD are characterized by a higher burden of cognitive impairment and hallucinations. However, few studies have analyzed the clinical characteristics of PD patients according to the timeline of RBD onset.

METHODS

PD patients have been retrospectively enrolled. Presence and onset of probable RBD (pRBD) has been evaluated using RBD Screening Questionnaire (score ≥ 6). Presence of Mild Cognitive Impairment (MCI) at baseline has been evaluated using the MDS criteria level II. Presence of motor complications and hallucinations has been evaluated at a 5-year follow-up.

RESULTS

A total of 115 PD patients (65 men, 56.5%; mean age 62.5 ± 9.7 years; mean disease duration 3.7 ± 3.9 years) have been enrolled. Out of these, 63 fulfilled the diagnosis of pRBD (54.8%) with 21 (33.3%) reporting the RBD onset before the onset of the motor symptoms (PD-RBDpre), and 42 (66.7%) after the motor symptoms (PD-RBDpost). At enrolment presence of MCI was associated with PD-RBDpre patients (OR 5.04; 95% CI 1.33-19.05; p value 0.02). At follow-up, a higher risk of developing hallucinations was also associated with PD-RBDpre (OR 4.68; 95% CI 1.24-17.63; p = 0.022).

CONCLUSIONS

PD patients with RBD occurring before the onset of motor symptoms represent a subgroup of patients with a more severe cognitive phenotype and with a higher risk of developing hallucinations along the disease course, with significant implications in terms of prognostic stratification and therapeutic approach.

A data-driven approach to neuropsychological features in isolated REM behaviour disorder: A latent class analysis

Recent evidence demonstrated that neuropsychological assessment may be considered a valid marker of neurodegeneration in idiopathic REM sleep behaviour disorder (iRBD). However, little is known about the possible neuropsychological heterogeneity within the iRBD population. This retrospective study aimed to identify and describe different neuropsychological phenotypes in iRBD patients by means of a data-driven approach using latent class analysis. A total of 289 iRBD patients underwent a neuropsychological assessment evaluating cognitive domains: global cognition, language, short- and long-term memory, executive functions and visuospatial abilities. The presence of mild cognitive impairment (MCI) was also assessed. Latent class analysis was carried out to identify iRBD subtypes according to neuropsychological scores. The most parsimonious model identified three latent classes. Groups were labelled as follows: Class 2 "severely impaired" (n = 83/289): mean pathological scores in different tests, a high percentage of MCI multiple-domain and impairment in all neuropsychological domains. Class 1 "moderately impaired" (n = 44/289): mean neuropsychological score within the normal value, a high percentage of MCI (high risk to phenoconversion) and great impairment in the visuospatial domain. Class 3 "slightly impaired" (n = 162/289): no deficit worthy of attention except for short- and long-term memory. Our results suggest three different clinical phenotypes within the iRBD population. These findings may be relevant in the future for predicting the clinical trajectories of phenoconversion in iRBD.

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.

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.

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.

Predictors of RBD progression and conversion to synucleinopathies

Purpose of review

Rapid eye movement (REM) sleep behaviour disorder (RBD) is considered the expression of the initial neurodegenerative process underlying synucleinopathies and constitutes the most important marker of their prodromal phase. This article reviews recent research from longitudinal research studies in isolated RBD (iRBD) aiming to describe the most promising progression biomarkers of iRBD and to delineate the current knowledge on the level of prediction of future outcome in iRBD patients at diagnosis.

Recent findings

Longitudinal studies revealed the potential value of a variety of biomarkers, including clinical markers of motor, autonomic, cognitive, and olfactory symptoms, neurophysiological markers such as REM sleep without atonia and electroencephalography, genetic and epigenetic markers, cerebrospinal fluid and serum markers, and neuroimaging markers to track the progression and predict phenoconversion. To-date the most promising neuroimaging biomarker in iRBD to aid the prediction of phenoconversion is striatal presynaptic striatal dopaminergic dysfunction.

Summary

There is a variety of potential biomarkers for monitoring disease progression and predicting iRBD conversion into synucleinopathies. A combined multimodal biomarker model could offer a more sensitive and specific tool. Further longitudinal studies are warranted to iRBD as a high-risk population for early neuroprotective interventions and disease-modifying therapies.

Predictive risk factors of phenoconversion in idiopathic REM sleep behavior disorder: the Italian study "FARPRESTO"

Most patients with idiopathic REM sleep behavior disorder (iRBD) will develop an overt α-synucleinopathy over time, with a rate of phenoconversion of 73.5% after 12 years from diagnosis. Several markers of phenoconversion were identified; however, most studies investigated biomarkers separately, with retrospective study designs, in small cohorts or without standardized data collection methods. The risk FActoRs PREdictive of phenoconversion in idiopathic REM sleep behavior disorder: the Italian STudy (FARPRESTO) is a multicentric longitudinal retrospective and prospective study with a cohort of incident (prospective recruitment) and prevalent (retrospective recruitment) iRBD patients, whose primary aim is to stratify the risk of phenoconversion, through the systematic collection by means of electronic case report forms of different biomarkers. Secondary aims are to (1) describe the sociodemographic and clinical characteristics of patients with iRBD; (2) collect longitudinal data about the development of α-synucleinopathies; (3) monitor the impact of iRBD on quality of life and sleep quality; (4) assess the correlation between phenoconversion, cognitive performance, and loss of normal muscle atony during REM sleep; (5) identify RBD phenotypes through evaluating clinical, biological, neurophysiological, neuropsychological, and imaging biomarkers; and (6) validate vPSG criteria for RBD diagnosis. The FARPRESTO study will collect a large and harmonized dataset, assessing the role of different biomarkers providing a unique opportunity for a holistic, multidimensional, and personalized approach to iRBD, with several possible application and impact at different levels, from basic to clinical research, and from prevention to management. The FARPRESTO has been registered at clinicaltrials.gov (NCT05262543).

Alerting network alteration in isolated rapid eye movement sleep behavior disorder patients with mild cognitive impairment

OBJECTIVE

Mild cognitive impairment (MCI) was found in 30-50% of the isolated REM sleep behavior disorder (iRBD) patients. Furthermore, it is known that patients with Parkinson's disease have attention network defects. Given that iRBD is known to be the prodromal disease of α-synucleinopathies, our aim was to investigate whether there are attention network dysfunctions in iRBD patients following the presence of MCI.

METHODS

14 healthy controls, 48 iRBD patients, 24 with MCI and 24 without MCI, were included in this study. Attention network task (ANT) was used to assess alerting, orienting, and executive control networks. Event-related potentials (ERPs) and behavioral performances were recorded during the ANT. Parietal N1 and P3 components were analyzed to find effects of the three attention networks.

RESULTS

IRBD patients without MCI showed neuropsychological, behavioral, and ERP results similar to those of healthy controls. On the other hand, iRBD patients with MCI showed a general decline in cognitive domains with no alerting effect (controls, p = 0.043; iRBD-noMCI, p = 0.014; iRBD-MCI, p = 0.130) while preserving orienting and executive control effect. Furthermore, iRBD patients with MCI had impairments in executive function and verbal memory domains, compared to iRBD patients without MCI.

CONCLUSIONS

Our findings indicate that when cognition is reduced to MCI levels in iRBD patients, the attention network, especially the alerting component, is impaired. The attention network and cognition, on the other hand, can be preserved in iRBD patients due to the compensatory mechanism.

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.

Neurophysiological evaluation of visual function in iRBD: potential role in stratifying RBD conversion risk

STUDY OBJECTIVES

To evaluate neurophysiological alterations of visual function in idiopathic REM sleep Behavior Disorder (iRBD) both as markers and predictors of neurodegenerative disorders.

METHODS

In a longitudinal follow-up study of 46 consecutive iRBD patients (follow-up duration 8.4 ± 3.4 years), the baseline parameters in luminance-contrast pattern (VEPp), red-green color (VEPc) and motion-onset (VEPm) Visual Evoked Potentials in iRBD were compared to early (ePD) and advanced (aPD) Parkinson's Disease subjects. Parameters of latency and amplitude of iRBD converters to neurodegenerative disease were compared with those of the non-converters.

RESULTS

The VEP P100 mean latency values for both eyes and for both stimulation checks (30' and 15') were significantly longer in all the three groups of patients as compared to controls; moreover latencies were longer in aPD than in the iRBD group who did not differ from the ePD group. The same held true when we analyzed the number of abnormal subjects belonging to each diagnostic group with a higher number of abnormal subjects in the aPD group compared to both the ePD and in iRBD groups. Chromatic and motion potentials were not different from controls and did not differ in the 3 diagnostic groups. The iRBD subjects who converted to a neurodegenerative disorder showed longer P100 latencies and a higher occurrence of VEPp abnormalities than those who did not convert. Again chromatic and motion VEPs were not different depending on conversion.

CONCLUSIONS

In iRBD patients the detection of an abnormal VEPp should be considered as a red flag for possible synnucleinopathy, eventually contributing in stratifying the risk of phenoconversion.

NREM sleep arousal-related disorders reflect cognitive impairment in Parkinson's disease

BACKGROUND

Sleep disorders and cognitive impairment are frequently reported in Parkinson's disease (PD) as non-motor disabling symptoms. While it is known that REM sleep Behaviour Disorder (RBD) in PD is associated with motor and cognitive decline, little is known about the neurobiological significance of NREM sleep arousal-related disorders.

OBJECTIVES

to evaluate the cognitive and clinical correlates of arousal-related disorders in PD.

METHODS

Clinical data and video-polysomnography were analysed from one hundred-seventy consecutive subjects with PD. Based on the neuropsychological assessment, the subjects were divided into three groups: no cognitive impairment (PD; n = 58), mild cognitive impairment (PD-MCI; n = 58) and overt dementia (PDD; n = 54).

RESULTS

Arousal-related disorders by history were reported in 32.9% of the subjects: 10.3% PD, 31.6% PD-MCI and 59.3% PDD (p = 0.001). Video-PSG captured arousal-related disorders in 1.7% PD, 21.2% MCI-PD and 35.6% PDD (p = 0.001). Arousal-related disorders and RBD were recorded in the same night in 7.7% PD, 9.8% MCI-PD and 15.6% PDD (p = 0.04). Patients with arousal-related disorders captured at V-PSG have a longer disease duration (p = 0.003), higher UPDRS score (p = 0.039), longer duration of treatment with levodopa (p = 0.017) and dopamine agonists (p = 0.018), worse H&Y staging (p = 0.001), lower MMSE score (p = 0.019) and more frequently hallucinations (p = 0.004). In multivariate analysis, cognitive impairment significantly increases the risk of arousal-related disorders (OR 3.387-95% CI 1.395-8.220, p = 0.007).

CONCLUSION

Arousal-related disorders appear to be a marker of cognitive decline in PD. Recognizing arousal-related disorders should make clinicians aware of a possible cognitive decline in PD and eventually modify the therapeutic approach.