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Summary Background Isolated rapid-eye-movement (REM) sleep behaviour disorder (IRBD) can be part of the prodromal stage of the α-synucleinopathies Parkinson's disease and dementia with Lewy bodies. Real-time quaking-induced conversion (RT-QuIC) analysis of CSF has high sensitivity and specificity for the detection of misfolded α-synuclein in patients with Parkinson's disease and dementia with Lewy bodies. We investigated whether RT-QuIC could detect α-synuclein in the CSF of patients with IRBD and be used as a biomarker of prodromal α-synucleinopathy. Methods In this longitudinal observational study, CSF samples were obtained by lumbar puncture from patients with video polysomnography-confirmed IRBD recruited at a specialised sleep disorders centre in Barcelona, Spain, and from controls free of neurological disease. CSF samples were stored until analysed using RT-QuIC. After lumbar puncture, participants were assessed clinically for neurological status every 3–12 months. Rates of neurological disease-free survival were estimated using the Kaplan-Meier method. Disease-free survival rates were assessed from the date of lumbar puncture to the date of diagnosis of any neurodegenerative disease, or to the last follow-up visit for censored observations. Findings 52 patients with IRBD and 40 healthy controls matched for age (p=0·20), sex (p=0·15), and duration of follow-up (p=0·27) underwent lumbar puncture between March 23, 2008, and July 16, 2017. The CSF α-synuclein RT-QuIC assay was positive in 47 (90%) patients with IRBD and in four (10%) controls, resulting in a sensitivity of 90·4% (95% CI 79·4–95·8) and a specificity of 90·0% (95% CI 76·9–96·0). Mean follow-up from lumbar puncture until the end of the study (July 31, 2020) was 7·1 years (SD 2·8) in patients with IRBD and 7·7 years (2·9) in controls. During follow-up, 32 (62%) patients were diagnosed with Parkinson's disease or dementia with Lewy bodies a mean 3·4 years (SD 2·6) after lumbar puncture, of whom 31 (97%) were α-synuclein positive at baseline. Kaplan-Meier analysis showed that patients with IRBD who were α-synuclein negative had lower risk for developing Parkinson's disease or dementia with Lewy bodies at 2, 4, 6, 8, and 10 years of follow-up than patients with IRBD who were α-synuclein positive (log-rank test p=0·028; hazard ratio 0·143, 95% CI 0·019–1·063). During follow-up, none of the controls developed an α-synucleinopathy. Kaplan-Meier analysis showed that participants who were α-synuclein negative (ie, five patients with IRBD plus 36 controls) had lower risk of developing Parkinson's disease or dementia with Lewy bodies at 2, 4, 6, 8 and 10 years after lumbar puncture than participants who were α-synuclein positive (ie, 47 patients with IRBD plus four controls; log-rank test p Interpretation In patients with IRBD, RT-QuIC detects misfolded α-synuclein in the CSF with both sensitivity and specificity of 90%, and α-synuclein positivity was associated with increased risk of subsequent diagnosis of Parkinson's disease or dementia with Lewy bodies. Detection of α-synuclein in the CSF represents a potential prodromal marker of Parkinson's disease and dementia with Lewy bodies. If these findings are replicated in additional cohorts, detection of CSF α-synuclein by RT-QuIC could be used to enrich IRBD cohorts in neuroprotective trials, particularly when assessing interventions that target α-synuclein. Funding Department of Health and Social Care Policy Research Programme, the Scottish Government, and the Weston Brain Institute.

INTRODUCTION: In vivo PET studies in patients with isolated REM sleep behavior disorder (iRBD) have shown presence of neuroinflammation (microglial activation) in the substantia nigra, and reduced cortical acetylcholinesterase activity, suggestive of cholinergic dysfunction, that was more widespread in patients with poorer cognitive performances. This study aimed to explore whether reduced cortical acetylcholinesterase activity in iRBD is linked to microglial activation in the substantia innominata (SI), the major source of cholinergic input to the cortex.METHODS: We used 11C(R)-PK11195 and 11C-Donepezil PET to assess levels of activated microglia and cholinergic function, respectively, in 19 iRBD patients. 11C(R)-PK11195 binding potential (BPND) and 11C-Donepezil distribution volume ratio (DVR) values were correlated using the Pearson statistic.RESULTS: We found that a lower cortical 11C-Donepezil DVR correlated with a higher 11C(R)-PK11195 BPND in the SI (r = -0.48, p = 0.04). At a voxel level, the strongest negative correlations were found in the frontal and temporal lobes.CONCLUSION: Our results suggest that reduced cortical acetylcholinesterase activity observed in our iRBD patients could be linked to the occurrence of neuroinflammation in the SI. Early modulation of microglial activation might therefore preserve cortical cholinergic functions in these patients.

Background: The majority of patients diagnosed with idiopathic rapid eye movement sleep behaviour disorder (iRBD) progress over time to a Lewy-type α-synucleinopathy such as Parkinson's disease or dementia with Lewy bodies. This in vivo molecular imaging study aimed to investigate if extrastriatal monoaminergic systems are affected in iRBD patients and if this coincides with neuroinflammation. Methods: We studied twenty-one polysomnography-confirmed iRBD patients with 18F-DOPA and 11C-PK11195 positron emission tomography (PET) to investigate extrastriatal monoaminergic function and microglial activation. Twenty-nine healthy controls (n = 9 18F-DOPA and n = 20 11C-PK11195) were also investigated. Analyses were performed within predefined regions of interest and at voxel-level with Statistical Parametric Mapping. Results: Regions of interest analysis detected monoaminergic dysfunction in iRBD thalamus with a 15% mean reduction of 18F-DOPA Ki values compared to controls (mean difference = −0.00026, 95% confidence interval [−0.00050 to −0.00002], p-value = 0.03). No associated thalamic changes in 11C-PK11195 binding were observed. Other regions sampled showed no 18F-DOPA or 11C-PK11195 PET differences between groups. Voxel-level interrogation of 11C-PK11195 binding identified areas with significantly increased binding within the occipital lobe of iRBD patients. Conclusion: Thalamic monoaminergic dysfunction in iRBD patients may reflect terminal dysfunction of projecting neurons from the locus coeruleus and dorsal raphe nucleus, two structures that regulate REM sleep and are known to be involved in the early phase of PD. The observation of significantly raised microglial activation in the occipital lobe of these patients might suggest early local Lewy-type α-synuclein pathology and possibly an increased risk for later cognitive dysfunction.

Introduction: Glucocerebrosidase (GBA) gene variants are associated with the development of the Lewy body disorders (LBD) Parkinson disease (PD) and dementia with Lewy bodies (DLB). Idiopathic REM sleep behavior disorder (IRBD) represents prodromal LBD in most instances. We investigated whether GBA variants are overrepresented in IRBD and if their presence shortens the time to conversion to clinically defined LBD. Methods: All GBA coding exons from 69 polysomnography-confirmed IRBD patients and 84 matched controls were sequenced by the Sanger method. Results: Seven missense variants (E326K, L444P, A446T, A318G, R329C, T369M, N3705) were identified in eight (11.6%) IRBD patients and in one (1.2%) control (P = 0.026). After a mean follow-up of 8.9 3.8 years from IRBD diagnosis, five subjects with GBA variants developed LBD (3 DLB and 2 PD) and three remained disease-free. The risk of developing a LBD was similar in IRBD subjects with GBA variants than in those without variants (log rank test, p = 0.935). Conclusions: In IRBD, GBA variants are 1) more frequent when compared to controls, 2) associated with impending PD and DLB but 3) not indicative of a short-term risk for LBD after IRBD diagnosis. IRBD patients carrying GBA variants could be studied with disease-modifying interventions aiming to restore the GBA metabolic pathway. (C) 2018 Elsevier Ltd. All rights reserved.

Summary Background We postulated that idiopathic rapid-eye-movement (REM) sleep behaviour disorder (IRBD) represents the prodromal phase of a Lewy body disorder and that, with sufficient follow-up, most cases would eventually be diagnosed with a clinical defined Lewy body disorder, such as Parkinson's disease (PD) or dementia with Lewy bodies (DLB). Methods Patients from an IRBD cohort recruited between 1991 and 2003, and previously assessed in 2005, were followed up during an additional period of 7 years. In this original cohort, we sought to identify the nature and frequency of emerging defined neurodegenerative syndromes diagnosed by standard clinical criteria. We estimated rates of survival free from defined neurodegenerative disease by means of the Kaplan-Meier method. We further characterised individuals who remained diagnosed as having only IRBD, through dopamine transporter (DAT) imaging, transcranial sonography (TCS), and olfactory testing. We did a neuropathological assessment in three patients who died during follow-up and who had the antemortem diagnosis of PD or DLB. Findings Of the 44 participants from the original cohort, 36 (82%) had developed a defined neurodegenerative syndrome by the 2012 assessment (16 patients were diagnosed with PD, 14 with DLB, one with multiple system atrophy, and five with mild cognitive impairment). The rates of neurological-disease-free survival from time of IRBD diagnosis were 65·2% (95% CI 50·9 to 79·5) at 5 years, 26·6% (12·7 to 40·5) at 10 years, and 7·5% (−1·9 to 16·9) at 14 years. Of the four remaining neurological-disease-free individuals who underwent neuroimaging and olfactory tests, all four had decreased striatal DAT uptake, one had substantia nigra hyperechogenicity on TCS, and two had impaired olfaction. In three patients, the antemortem diagnoses of PD and DLB were confirmed by neuropathological examination showing widespread Lewy bodies in the brain, and α-synuclein aggregates in the peripheral autonomic nervous system in one case. In these three patients, neuronal loss and Lewy pathology (α-synuclein-containing Lewy bodies and Lewy neurites) were found in the brainstem nuclei that regulate REM sleep atonia. Interpretation Most IRBD individuals from our cohort developed a Lewy body disorder with time. Patients who remained disease-free at follow-up showed markers of increased short-term risk for developing PD and DLB in IRBD, such as decreased striatal DAT binding. Our findings indicate that in most patients diagnosed with IRBD this parasomnia represents the prodromal phase of a Lewy body disorder. IRBD is a candidate for the study of early events and progression of this prodromal phase, and to test disease-modifying strategies to slow or stop the neurodegenerative process. Funding None.

Summary Background Patients with idiopathic rapid-eye-movement sleep behaviour disorder (IRBD) may develop neurodegenerative conditions associated with substantia nigra dysfunction such as Parkinson's disease. In patients with Parkinson's disease, 123 I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane ( 123 I-FP-CIT) SPECT detects striatal dopamine dysfunction resulting from nigral pathology whereas transcranial sonography (TCS) shows increased substantia nigra echogenic size, even before parkinsonism is clinically evident. We postulated that these neuroimaging changes could occur in a proportion of IRBD individuals who might then be at increased risk for development of a neurodegenerative disorder associated with substantia nigra dysfunction. Methods In our prospective study, we identified patients with IRBD from individuals referred to our sleep disorders centre in Barcelona, Spain. At baseline, we assessed dopamine transporter uptake by use of 123 I-FP-CIT SPECT, and estimated echogenicity of the substantia nigra by use of TCS. After a follow-up of 2·5 years, participants were clinically assessed to establish whether they had developed neurodegenerative syndromes. Data were compared with those of matched healthy controls. Findings 43 individuals with IRBD agreed to participate in the study. We found reduced 123 I-FP-CIT binding in the striatum (p=0·045) in 17 (40%) of 43 participants compared with 18 controls, and substantia nigra hyperechogenicity in 14 (36%) of 39 participants with IRBD, compared with 16 (11%) of 149 controls (p=0·0002). Tracer uptake reduction was more pronounced in the putamen than it was in the caudate nucleus. 27 (63%) participants had reduced 123 I-FP-CIT binding or substantia nigra hyperechogenicity at baseline. Eight (30%) of these participants developed a neurodegenerative disorder (five Parkinson's disease, two dementia with Lewy bodies, and one multiple system atrophy). Individuals with normal neuroimaging results remained disease-free. Sensitivity of combined 123 I-FP-CIT SPECT and TCS to predict conversion to synucleinopathy after 2·5 years was 100% and specificity was 55%. Interpretation In patients with IRBD, 123 I-FP-CIT SPECT and TCS can detect subclinical changes much the same as those typically seen in patients with early Parkinson's disease. Decreased striatal 123 I-FP-CIT binding and substantia nigra hyperechogenicity might be useful markers to identify individuals at increased risk for development of synucleinopathies. Funding None.

Objective Patients with idiopathic rapid eye movement (REM) sleep behavior disorder (IRBD) may show electroencephalographic (EEG) slowing reflecting cortical dysfunction and are at risk for developing neurological conditions characterized by cognitive dysfunction including mild cognitive impairment (MCI), dementia with Lewy bodies and Parkinson’s disease with associated dementia. We hypothesized that those IRBD patients who later developed MCI had pronounced cortical EEG slowing at presentation. Methods Power EEG spectral analysis was blindly quantified from the polysomnographic studies of 23 IRBD patients without cognitive complaints and 10 healthy controls without RBD. After a mean clinical follow-up of 2.40 ± 1.55 years, 10 patients developed MCI (RBD + MCI) and the remaining 13 remained idiopathic. Results Patients with RBD + MCI had marked EEG slowing (increased delta and theta activity) in central and occipital regions during wakefulness and REM sleep, particularly in the right hemisphere, when compared with controls and, to a lesser extent, with IRBD subjects who remained idiopathic. The EEG spectral pattern of the RBD + MCI group was similar to that seen in patients with dementia with Lewy bodies and Parkinson’s disease associated with dementia. Conclusion Our findings suggest that the presence of marked EEG slowing on spectral analysis might be indicative of the short-term development of MCI in patients initially diagnosed with IRBD.