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Abstract We investigated the biomarker profile of neurodegeneration, Alzheimer’s and Lewy body pathology in the CSF of 148 polysomnography-confirmed patients with isolated REM sleep behavior disorder (IRBD), a condition that precedes Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). We assessed misfolded α-synuclein (AS) by RT-QuIC assay, amyloid-beta peptides (Aβ42 and Aβ40), phosphorylated tau (p-tau), and total tau (t-tau) by CLEIA and neurofilament light chain (NfL) by ELISA. We detected AS in 75.3% of patients, pathologically decreased Aβ42/Aβ40 ratio in 22.5%, increased p-tau in 15.5%, increased t-tau in 14.9%, and elevated NfL in 14.7%. After a mean follow-up of 2.48 ± 2.75 years, 47 (38.1%) patients developed PD (n = 24) or DLB (n = 23). At CSF collection, AS positivity [HR 4.05 (1.26–12.99), p = 0.019], mild cognitive impairment [3.86 (1.96–7.61), p

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.

ObjectiveTo estimate the risk for developing a defined neurodegenerative syndrome in a large cohort of idiopathic REM sleep behavior disorder (IRBD) patients with long follow-up.MethodsUsing the Kaplan-Meier method, we estimated the disease-free survival rate from defined neurodegenerative syndromes in all the consecutive IRBD patients diagnosed and followed-up in our tertiary referal sleep center between November 1991 and July 2013.ResultsThe cohort comprises 174 patients with a median age at diagnosis of IRBD of 69 years and a median follow-up of four years. The risk of a defined neurodegenerative syndrome from the time of IRBD diagnosis was 33.1% at five years, 75.7% at ten years, and 90.9% at 14 years. The median conversion time was 7.5 years. Emerging diagnoses (37.4%) were dementia with Lewy bodies (DLB) in 29 subjects, Parkinson disease (PD) in 22, multiple system atrophy (MSA) in two, and mild cognitive impairment (MCI) in 12. In six cases, in whom postmortem was performed, neuropathological examination disclosed neuronal loss and widespread Lewy-type pathology in the brain in each case.ConclusionsIn a large IRBD cohort diagnosed in a tertiary referal sleep center, prolonged follow-up indicated that the majority of patients are eventually diagnosed with the synucleinopathies PD, DLB and less frequently MSA. IRBD represented the prodromal period of these conditions. Our findings in IRBD have important implications in clinical practice, in the investigation of the early pathological events occurring in the synucleinopathies, and for the design of interventions with potential disease-modifying agents.

Summary: Background: Idiopathic rapid eye movement (REM) sleep behaviour disorder (IRBD) represents the prodromal stage of Lewy body disorders (Parkinson's disease (PD) and dementia with Lewy bodies (DLB)) which are linked to variations in circulating cell-free mitochondrial DNA (cf-mtDNA). Here, we assessed whether altered cf-mtDNA release and integrity are already present in IRBD. Methods: We used multiplex digital PCR (dPCR) to quantify cf-mtDNA copies and deletion ratio in cerebrospinal fluid (CSF) and serum in a cohort of 71 participants, including 1) 17 patients with IRBD who remained disease-free (non-converters), 2) 34 patients initially diagnosed with IRBD who later developed either PD or DLB (converters), and 3) 20 age-matched controls without IRBD or Parkinsonism. In addition, we investigated whether CD9-positive extracellular vesicles (CD9-EVs) from CSF and serum samples contained cf-mtDNA. Findings: Patients with IRBD, both converters and non-converters, exhibited more cf-mtDNA with deletions in the CSF than controls. This finding was confirmed in CD9-EVs. The high levels of deleted cf-mtDNA in CSF corresponded to a significant decrease in cf-mtDNA copies in CD9-EVs in both IRBD non-converters and converters. Conversely, a significant increase in cf-mtDNA copies was found in serum and CD9-EVs from the serum of patients with IRBD who later converted to a Lewy body disorder. Interpretation: Alterations in cf-mtDNA copy number and deletion ratio known to occur in Lewy body disorders are already present in IRBD and are not a consequence of Lewy body disease conversion. This suggests that mtDNA dysfunction is a primary molecular mechanism of the pathophysiological cascade that precedes the full clinical motor and cognitive manifestation of Lewy body disorders. Funding: Funded by Michael J. Fox Foundation research grant MJFF-001111. Funded by MICIU/AEI/10.13039/501100011033 “ERDF A way of making Europe”, grants PID2020-115091RB-I00 (RT) and PID2022-143279OB-I00 (ACo). Funded by Instituto de Salud Carlos III and European Union NextGenerationEU/PRTR, grant PMP22/00100 (RT and ACo). Funded by AGAUR/Generalitat de Catalunya, grant SGR00490 (RT and ACo). MP has an FPI fellowship, PRE2018-083297, funded by MICIU/AEI/10.13039/501100011033 “ESF Investing in your future”.

Abstract Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is a prodromal stage of Lewy-type synucleinopathies (LTS), which can present either with an initial predominant parkinsonism (Parkinson’s disease (PD)) or dementia (dementia with Lewy bodies (DLB)). To provide insights into the underlying pathogenic mechanisms, the lipoprotein and protein glycosylation profile of 82 iRBD patients, collected before and/or after their conversion to an overt LTS, and 29 matched control serum samples were assessed by nuclear magnetic resonance (NMR) spectroscopy. Data were statistically analyzed to identify altered metabolites and construct predictive models. Univariant analysis detected no differences between iRBD patients with an LTS compared to controls. However, significant differences were found when the analysis distinguished between iRBD patients that manifested initially predominant parkinsonism (pre-PD) or dementia (pre-DLB). Significant differences were also found in the analysis of paired iRBD samples pre- and post-LTS diagnosis. Predictive models were built and distinguished between controls and pre-DLB patients, and between pre-DLB and pre-PD patients. This allowed a prediction of the possible future clinical outcome of iRBD patients. We provide evidence of altered lipoprotein and glycosylation profiles in subgroups of iRBD patients. Our results indicate that metabolic alterations and inflammation are involved in iRBD pathophysiology, and suggest biological differences underlying the progression of LTS in iRBD patients. Our data also indicate that profiling of serum samples by NMR may be a useful tool for identifying short-term high-risk iRBD patients for conversion to parkinsonism or dementia.

Objective: In this study we investigate cortical and subcortical gray matter structure in patients with Idiopathic REM-sleep behavior disorder (IRBD), and their relation to cognitive performance.Methods: This study includes a sample of 20 patients with polysomnography-confirmed IRBD and 27 healthy controls that underwent neuropsychological and T1-weighted MRI assessment. FreeSurfer was used to estimate cortical thickness, subcortical volumetry (version 5.1), and hippocampal subfields segmentation (version 6.0). FIRST, FSL's model-based segmentation/registration tool was used for hippocampal shape analysis.Results: Compared with healthy subjects, IRBD patients showed impairment in facial recognition, verbal memory, processing speed, attention, and verbal naming. IRBD patients had cortical thinning in left superior parietal, post-central, and fusiform regions, as well as in right superior frontal and lateral occipital regions. Volumetric and shape analyses found right hippocampal atrophy in IRBD, specifically in posterior regions. Hippocampal subfields exploratory analysis identified significant differences in the right CA1, molecular layer, granule cell layer of dentate gyrus, and CA4 of this patients. No correlations were found between cognitive performance and brain atrophy.Conclusion: This work confirms the presence of posterior based cognitive dysfunction, as well as cortical and right hippocampal atrophy in IRBD patients.