Body-First Subtype of Parkinson's Disease with Probable REM-Sleep Behavior Disorder Is Associated with Non-Motor Dominant Phenotype

Hypothalamic volume, sleep, and APOE genotype in cognitively healthy adults

INTRODUCTION

Sleep dysfunction in those at higher risk of dementia may be associated with early structural changes to the hypothalamus.

METHODS

We used multivariate regression to analyze self-reported sleep (Pittsburgh Sleep Quality Index [PSQI]) from cognitively healthy participants in the PREVENT Dementia and Alzheimer's and Families (ALFA) studies (n = 1939), stratified by apolipoprotein E (APOE) genotype as homozygotes, heterozygotes, and non-carriers. FreeSurfer was used to extract hypothalamic subunit volumes from T1-weighted magnetic resonance images.

RESULTS

APOE ε4 homozygotes had a larger anterior-superior hypothalamus compared to heterozygotes and non-carriers, an effect which was driven by younger people in the cohort. APOE ε4 carriers had a higher PSQI global score after age 55, and smaller anterior-superior and tubular-superior subunits were associated with more sleep disturbances. Sleep duration and efficiency worsened with age, but only in participants with a small anterior-inferior hypothalamus.

DISCUSSION

This suggests that aging and APOE ε4 are associated with hypothalamic changes, highlighting mechanisms linking sleep dysfunction to dementia.

HIGHLIGHTS

Apolipoprotein E (APOE) ε4 homozygotes ha a larger anterior-superior hypothalamus. APOE ε4 carriers have worse sleep, but only after age 55. Worse sleep in APOE ε4 carriers was associated with smaller hypothalamic subunits. Higher age was associated with worse sleep in people with a small hypothalamus.

Longitudinal associations of lipid profiles with sleep disorders in patients with Parkinson's disease

To examine the associations of apolipoprotein E (APOE) carrier status and lipid profiles with sleep disorders, including excessive daytime sleepiness (EDS) and probable rapid eye movement sleep behavior disorder (pRBD), among patients with early Parkinson's disease (PD) over 5-year follow-up periods. The Parkinson's Progression Markers Initiative is a multicenter cohort study based on an ongoing and open-ended registry. Data from baseline and 5-year follow-up visits from participants of de novo PD were analyzed. Longitudinal associations of APOE carrier status and lipid profiles with sleep disorders were estimated via linear mixed-effects models. A total of 657 participants with complete APOE genotypes were enrolled at baseline. Among them, 153 (25.3%) had available lipid profiles at baseline. In the linear mixed-effects models, baseline APOE ε2/ε3/ε4 carrier status did not exhibit significant associations with EDS and pRBD (all p > 0.05) in all models. However, reduced high-density lipoprotein (HDL) and elevated triglycerides (TG) were associated with developing EDS (β = -0.04, 95% CI: -0.07, -0.00) and pRBD (β = 0.01, 95% CI: 0.00, 0.02) in PD patients, respectively. In the APOE ε4+ subgroup, decreased HDL and increased TG displayed substantial associations with developing EDS and sleep disorders (all p < 0.05) in all models, respectively, whereas no significant differences were noted in the APOE ε4- subgroup (all p > 0.05). Our study did not demonstrate a clear association between APOE ε2/ε3/ε4 and sleep disorders in PD patients. However, the presence of APOE ε4 was associated with changes in lipid profiles, notably affecting TG and HDL levels.

Four questions to predict cognitive decline in de novo Parkinson's disease

Early identification of cognitive decline (CD) in de novo Parkinson's disease (PD) is crucial for choosing appropriate therapies and recruiting for clinical trials. However, existing prognostic models lack flexibility, scalability and require costly instrumentation. This study explores the utility of standard clinical questionnaires and criteria to predict CD in de novo PD. A total of 186 patients from the Parkinson Progression Markers Initiative (PPMI) and 48 patients from the Biomarkers of Parkinson's Disease project (BIO-PD) underwent clinical interviews, comprehensive tests, and questionnaires. A model based only on age of disease onset, history of stroke, history of fainting, and vocalization during dreams predicted CD in 2 and 4-year horizons with an area under curve (AUC) of 70% ± 10% standard deviation (cross-validated PPMI), 79% (overall PPMI), and 78% (validation in BIO-PD). This approach enables rapid preliminary screening using just four simple questions, achieving predictive accuracy comparable to instrumentation-based methods while reducing assessment time.

Plasma GFAP and NfL associate with cerebral glucose metabolism in putative brain-first and body-first Parkinson's disease subtypes

The recently proposed body-first and brain-first subtypes are classified based on the initial localization of α-synuclein inclusions. This study investigated plasma biomarkers and cerebral glucose metabolism characteristics in putative brain-first and body-first subtypes in PD subjects. PD patients without possible RBD (PDpRBD-) (n = 58) and with possible RBD symptoms discovered before motor symptoms (PDpRBD+) (n = 43) were recruited. Single-molecule array (SimoA) was used for measuring plasma biomarkers, including glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL), Tau and phosphorylated-tau 181 (pTau-181). All participants underwent 18F-fluorodeoxyglucose (FDG) PET scans. Compared to PDpRBD- patients, PDpRBD+ patients exhibited significantly increased plasma GFAP levels and reduced 18F-FDG uptake in cortical regions. Notably, plasma GFAP and NfL levels correlated with cerebral glucose metabolism in PDpRBD- patients. Our study identified the association between plasma GFAP and NfL levels and cerebral glucose metabolism in PDpRBD- patients. Further large-scale longitudinal studies are required.

Wider and faster degeneration of white matter in Parkinson's disease with possible REM sleep behaviour disorder

BACKGROUND

In Parkinson's disease (PD), rapid eye movement (REM) sleep behaviour disorder (RBD) signifies a poorer prognosis, yet its impact on white matter (WM) degeneration remains unclear. The study examined the effect of RBD on WM alterations in PD progression.

METHODS

The study included 45 PD patients with possible RBD (PD-pRBD), 38 PD patients without possible RBD (PD-npRBD), and 79 healthy controls (HC). All patients underwent clinical assessments and diffusion MRI scans at least once a year for up to 4 visits. 79 HC underwent the same protocol at baseline. WM metrics, including fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), were calculated using tract-based spatial statistics. Linear mixed-effects models were conducted to examine the changes in clinical features and WM fibers.

RESULTS

At baseline, PD-npRBD showed increased RD in several regions, predominantly in bilateral uncinate fasciculus (UF) and inferior longitudinal fasciculus (ILF), compared to HC (PFDR<0.05). During follow-up, PD-npRBD had further FA decrease in left UF and ILF (PFDR<0.05). PD-pRBD showed reduced FA in several regions relative to HC at baseline (PFDR<0.05), and faster FA decline in left UF and ILF than PD-npRBD during follow-up, with more extensive FA decrease in other regions such as anterior thalamic radiation and inferior fronto-occipital fasciculus (PFDR<0.05). Moreover, increased RD in the left corticospinal tract correlated with motor symptoms (p = 0.045) in PD-pRBD.

CONCLUSIONS

PD patients with pRBD demonstrated more extensive WM degeneration and accelerated degeneration in the left ILF and UF during the disease course. However, due to the lack of PSG verification, these results should be interpreted cautiously while directly relating to RBD. These findings provide new insights into the neural structural basis associated with the potential impact of RBD on PD progression.

Associations of cerebrospinal fluid monoamine metabolites with striatal dopamine transporter binding and 123I-meta-iodobenzylguanidine cardiac scintigraphy in Parkinson's disease: Multivariate analyses

Cerebrospinal fluid (CSF) homovanillic acid (HVA) and 5-hydroxyindole acetic acid (5-HIAA), dopamine and serotonin metabolites, are decreased in Parkinson's disease (PD). Although some reported associations between HVA and striatal dopamine transporter (DAT) or 5-HIAA and cardiac 123I-meta-iodobenzylguanidine (MIBG) findings, respectively, whether these are direct associations remained unknown. We retrospectively reviewed 57 drug-naïve patients with PD who underwent CSF analyses and DAT and cardiac MIBG imaging. Z-score of striatal DAT specific binding ratio (Z-SBR) was measured, and the positivity of MIBG abnormalities were judged by an expert. The mean age was 75.5 ± 8.7 years. Thirty-three were MIBG-positive and 24 were MIBG-negative. 5-HIAA levels were significantly lower in the MIBG-positive group. Logistic regression analysis showed that MIBG positivity was associated with 5-HIAA level (odds ratio = 0.751, p = 0.006) but not with age, sex, and HVA. DAT Z-SBR correlated with both HVA and 5-HIAA. Multiple regression analysis showed that HVA was the only significant variable associated with Z-SBR (t = 3.510, p < 0.001). We confirmed direct associations between 5-HIAA and cardiac MIBG, and between HVA and striatal DAT binding.

Disease progression subtypes of Parkinson's disease based on milestone events

BACKGROUND

Parkinson's disease (PD) demonstrates considerable heterogeneity in the manifestation of clinical symptoms and disease progression. Recently, six clinical milestones have been proposed to evaluate disease severity in PD. However, the identification of PD progression subtypes based on these milestone events has not yet been performed.

METHODS

Latent class analysis (LCA) was employed to identify subtypes of PD progression based on the timing of the first occurrence of six milestones within a 6-year follow-up period in Parkinson's Progression Markers Initiative (PPMI) database.

RESULTS

The study cohort consisted of 354 early PD patients, of whom 42.9% experienced at least one milestone within six years. LCA identified two distinct subtypes of PD progression: slow progression (83%) and rapid progression (17%). The total number of milestones over six years was significantly higher in the rapid progression subtype compared to the slow progression subtype (median: 3.00 vs. 0.00, p < 0.001). At baseline, the rapid progression subtype, compared to the slow progression subtype, was characterized by an older age at onset and more severe motor and non-motor symptoms. On biomarkers, the rapid progression subtype demonstrated elevated CSF p-tau and serum NFL, but decreased mean striatal DAT uptake. Five clinical variables (age, SDMT score, MDS-UPDRS I score, MDS-UPDRS II + III scores, and RBD) were selected to construct the predictive model. The original predictive model achieved an AUC of 0.82. In internal validation using bootstrap resampling, the model achieved an AUC of 0.82, with a 95%CI ranging from 0.76 to 0.87. The model's performance was acceptable regarding both calibration and clinical utility.

CONCLUSION

Approximately 17% of early PD patients exhibited the rapid progression subtype, characterized by the occurrence of more and earlier-onset milestones. The nomogram predictive model, incorporating five baseline clinical variables (age, SDMT score, MDS-UPDRS I score, MDS-UPDRS II + III scores, RBD), serves as a valuable tool for prognostic counseling and patient selection in PD clinical trials.

Orthostatic Hypotension: a clinical marker for the body-first subtype of patients with Parkinson's Disease

Our study aimed to investigate the clinical characteristics of PD patients stratified by OH status before and after levodopa challenge to explore the hypothesis that OH might serve as a clinical marker for the body-first subtype of PD. Supine and standing blood pressure were measured in a large cross-sectional cohort of PD patients at the OFF status before and after levodopa challenge test (LCT). Based on OH status, patients were divided into three groups: spontaneous OH (SOH), only levodopa-induced OH (LOH) and non-OH (NOH). Clinical characteristics and associated factors were compared among the groups. A total of 928 patients with a mean age of 62.4 years and average disease duration of 7.9 years were included. There were 224 (24.1%) patients with SOH, 321 (34.6%) with LOH, and 383 (41.3%) with NOH. Compared to NOH, both SOH and LOH were associated with older age, motor fluctuations, and probable rapid eye movement sleep behavior disorder (pRBD). In addition, OH was more associated with cardiovascular and digestive dysfunction, disease severity and worse quality of life. Results of the current study suggest that PD patients developed OH which is more likely to comorbid with RBD, severe autonomic dysfunction and motor fluctuations, consistent with the body-first subtype of PD.

Insular and limbic abnormal functional connectivity in early-stage Parkinson's disease patients with autonomic dysfunction

Autonomic symptoms in Parkinson's disease result from variable involvement of the central and peripheral systems, but many aspects remain unclear. The analysis of functional connectivity has shown promising results in assessing the pathophysiology of Parkinson's disease. This study aims to investigate the association between autonomic symptoms and cortical functional connectivity in early Parkinson's disease patients using high-density EEG. 53 early Parkinson's disease patients (F/M 18/35) and 49 controls (F/M 20/29) were included. Autonomic symptoms were evaluated using the Scales for Outcomes in Parkinson's disease-Autonomic Dysfunction score. Data were recorded with a 64-channel EEG system. We analyzed cortical functional connectivity, based on weighted phase-lag index, in θ-α-β-low-γ bands. A network-based statistic was used to perform linear regression between Scales for Outcomes in Parkinson's disease-Autonomic Dysfunction score and functional connectivity in Parkinson's disease patients. We observed a positive relation between the Scales for Outcomes in Parkinson's disease-Autonomic Dysfunction score and α-functional connectivity (network τ = 2.8, P = 0.038). Regions with higher degrees were insula and limbic lobe. Moreover, we found positive correlations between the mean connectivity of this network and the gastrointestinal, cardiovascular, and thermoregulatory domains of Scales for Outcomes in Parkinson's disease-Autonomic Dysfunction. Our results revealed abnormal functional connectivity in specific areas in Parkinson's disease patients with greater autonomic symptoms. Insula and limbic areas play a significant role in the regulation of the autonomic system. Increased functional connectivity in these regions might represent the central compensatory mechanism of peripheral autonomic dysfunction in Parkinson's disease.

Disease progression in proposed brain-first and body-first Parkinson's disease subtypes

A new Parkinson's disease (PD) subtyping model has been recently proposed based on the initial location of α-synuclein inclusions, which divides PD patients into the brain-first subtype and the body-first subtype. Premotor RBD has proven to be a predictive marker of the body-first subtype. We found compared to PD patients without possible RBD (PDpRBD-, representing the brain-first subtype), PD patients with possible premotor RBD (PDpRBD+, representing the body-first subtype) had lower Movement Disorders Society Unified Parkinson's Disease Rating Scale part III (MDS UPDRS-III) score (p = 0.022) at baseline but presented a faster progression rate (p = 0.009) in MDS UPDRS-III score longitudinally. The above finding indicates the body-first subtype exhibited a faster disease progression in motor impairments compared to the brain-first subtype and further validates the proposed subtyping model.

Brain-first vs. body-first Parkinson's disease: An update on recent evidence

We recently proposed a new disease model of Parkinson's disease - the a-Synuclein Origin site and Connectome model. The model posits that the initial pathology starts either in the olfactory bulb or amygdala leading to a brain-first subtype, or in the enteric nervous system leading to a body-first subtype. These subtypes should be distinguishable early in the disease course on a range of imaging, clinical, and neuropathological markers. Here, we review recent original human studies, which tested the predictions of the model. Molecular imaging studies were generally in agreement with the model, whereas structural imaging studies, such as MRI volumetry, showed conflicting findings. Most large-scale clinical studies were supportive, reporting clustering of relevant markers of the body-first subtype, including REM-sleep behavior disorder, constipation, autonomic dysfunction, neuropsychiatric symptoms, and cognitive impairment. Finally, studies of a-synuclein deposition in antemortem and postmortem tissues revealed distribution of pathology, which generally supports the model.

Cognition and Other Non-Motor Symptoms in an At-Risk Cohort for Parkinson's Disease Defined by REM-Sleep Behavior Disorder and Hyposmia

Background

REM-sleep behavior disorder (RBD) and other non-motor symptoms such as hyposmia were proposed by the Movement Disorder Society as research criteria for prodromal Parkinson's disease (P-PD). Global cognitive deficit was later added.

Objective

To compare non-motor symptoms, focusing on cognition, between a P-PD group and a matched control group.

Methods

In this cross-sectional, case-control study, in a first set of analyses, we performed extensive cognitive testing on people with (n = 76) and a control group without (n = 195) probable RBD and hyposmia. Furthermore, we assessed motor and non-motor symptoms related to Parkinson's Disease (PD). After propensity score matching, we compared 62 P-PD with 62 age- and sex-matched controls. In addition, we performed regression analyses on the total sample (n = 271). In a second set of analyses, we used, a.o., the CUPRO to evaluate retrograde procedural memory and visuo-constructive functions.

Results

People with P-PD showed significantly poorer performances in global cognition, visuo-constructive and executive functions, mainly in mental flexibility (p < 0.001; p = 0.004; p = 0.003), despite similar educational levels (p = 0.415). We observed significantly more motor and non-motor symptoms (p < 0.001; p = 0.004), higher scores for depression (p = 0.004) and apathy (p < 0.001) as well as lower quality of life (p < 0.001) in P-PD.

CONCLUSIONS

Our findings confirm that global cognitive, executive, and visuo-constructive deficits define the P-PD group. In addition, depression, apathy, and lower quality of life were more prevalent in P-PD. If replicated in other samples, executive and visuo-constructive deficits should be considered in non-motor P-PD. Determining specific patterns will support early recognition of PD, secondary prevention of complications and the development of neuroprotective treatments.

Parkinson's Disease and Dementia with Lewy Bodies: One and the Same

The question whether Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) are expressions of the same underlying disease has been vigorously debated for decades. The recently proposed biological definitions of Lewy body disease, which do not assign any particular importance to the dopamine system over other degenerating neurotransmitter systems, has once more brought the discussion about different types of Lewy body disease to the forefront. Here, we briefly compare PDD and DLB in terms of their symptoms, imaging findings, and neuropathology, ultimately finding them to be indistinguishable. We then present a conceptual framework to demonstrate how one can view different clinical syndromes as manifestations of a shared underlying Lewy body disease. Early Parkinson's disease, isolated RBD, pure autonomic failure and other autonomic symptoms, and perhaps even psychiatric symptoms, represent diverse manifestations of the initial clinical stages of Lewy body disease. They are characterized by heterogeneous and comparatively limited neuronal dysfunction and damage. In contrast, Lewy body dementia, an encompassing term for both PDD and DLB, represents a more uniform and advanced stage of the disease. Patients in this category display extensive and severe Lewy pathology, frequently accompanied by co-existing pathologies, as well as multi-system neuronal dysfunction and degeneration. Thus, we propose that Lewy body disease should be viewed as a single encompassing disease entity. Phenotypic variance is caused by the presence of individual risk factors, disease mechanisms, and co-pathologies. Distinct subtypes of Lewy body disease can therefore be defined by subtype-specific disease mechanisms or biomarkers.

Luxembourg Parkinson's study -comprehensive baseline analysis of Parkinson's disease and atypical parkinsonism

Background

Deep phenotyping of Parkinson's disease (PD) is essential to investigate this fastest-growing neurodegenerative disorder. Since 2015, over 800 individuals with PD and atypical parkinsonism along with more than 800 control subjects have been recruited in the frame of the observational, monocentric, nation-wide, longitudinal-prospective Luxembourg Parkinson's study.

Objective

To profile the baseline dataset and to explore risk factors, comorbidities and clinical profiles associated with PD, atypical parkinsonism and controls.

Methods

Epidemiological and clinical characteristics of all 1,648 participants divided in disease and control groups were investigated. Then, a cross-sectional group comparison was performed between the three largest groups: PD, progressive supranuclear palsy (PSP) and controls. Subsequently, multiple linear and logistic regression models were fitted adjusting for confounders.

Results

The mean (SD) age at onset (AAO) of PD was 62.3 (11.8) years with 15% early onset (AAO < 50 years), mean disease duration 4.90 (5.16) years, male sex 66.5% and mean MDS-UPDRS III 35.2 (16.3). For PSP, the respective values were: 67.6 (8.2) years, all PSP with AAO > 50 years, 2.80 (2.62) years, 62.7% and 53.3 (19.5). The highest frequency of hyposmia was detected in PD followed by PSP and controls (72.9%; 53.2%; 14.7%), challenging the use of hyposmia as discriminating feature in PD vs. PSP. Alcohol abstinence was significantly higher in PD than controls (17.6 vs. 12.9%, p = 0.003).

Conclusion

Luxembourg Parkinson's study constitutes a valuable resource to strengthen the understanding of complex traits in the aforementioned neurodegenerative disorders. It corroborated several previously observed clinical profiles, and provided insight on frequency of hyposmia in PSP and dietary habits, such as alcohol abstinence in PD.Clinical trial registration: clinicaltrials.gov, NCT05266872.

REM Behavior Disorder: Implications for PD Therapeutics

PURPOSE

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia that occurs during REM sleep, characterized by REM sleep without atonia (RSWA) and dream enactment behavior (DEB). RBD is associated with several diseases and medications but most notably is a prodromal feature of synucleinopathies, including Parkinson's disease (PD). This article reviews RBD, its treatments, and implications for PD therapeutics.

RECENT FINDINGS

Recent research recognizes RBD as a prodromal marker of PD, resulting in expansion of basic science and clinical investigations of RBD. Current basic science research investigates the pathophysiology of RBD and explores animal models to allow therapeutic development. Clinical research has focused on natural history observation, as well as potential RBD treatments and their impact on sleep and phenoconversion to neurodegenerative disease. RBD serves as a fresh access point to develop both neuroprotective and symptomatic therapies in PD. These types of investigations are novel and will benefit from the more established basic science infrastructure to develop new interventions.

Minor hallucinations in Parkinson's disease with probable rapid eye movement sleep behavior disorder

Background

Rapid eye movement sleep behavior disorder (RBD) and minor hallucinations (MHs) are prevalent nonmotor symptoms in Parkinson's disease (PD). The purpose of this study was to explore the association of MHs in PD patients with probable RBD (pRBD).

Methods

This cross-sectional study included 291 patients diagnosed with PD. Patients who scored 6 or higher on the Rapid Eye Movement Behavior Disorder (RBD) Screening Questionnaire were defined as pRBD. A comprehensive evaluation was performed for all patients, including the collection of demographic information, clinical assessment, and MH features.

Results

Among the 291 PD patients, 69 (23.7%) had pRBD. MHs were observed in 35 (50.7%) patients with pRBD, significantly higher than 29.7% in patients without RBD (p = 0.015). The main type of MHs in pRBD was presence hallucinations with variable content. Patients with pRBD and MHs tended to be older, had a longer disease duration, and were more likely to take levodopa or dopamine-receptor agonists. Besides, the pRBD with MHs group had higher scores on the Nonmotor Symptoms Questionnaire (NMS-Quest) and Hamilton Anxiety Scale (HAMA). Binary logistic regression analysis revealed that longer disease duration and higher NMS-Quest scores were associated with MHs in PD patients with pRBD.

Conclusion

A high prevalence of MHs was observed in PD patients with pRBD. The main type of MHs in pRBD was presence hallucinations. MHs in PD with RBD are mainly associated with disease duration and severity of nonmotor symptoms. These findings provide new insights into the interaction between MHs and RBD.

Presence but not the timing of onset of REM sleep behavior disorder distinguishes evolution patterns in Parkinson's disease

BACKGROUND

Rapid eye movement (REM) sleep behavior disorder (RBD) could develop preceding or come after motor symptoms during Parkinson's disease (PD). It remains unknown that whether PD with different timing of RBD onset relative to motor symptoms suggests different spatiotemporal sequence of neurodegeneration. This study aimed to explore the sequence of disease progression in crucially involved brain regions in PD with different timing of RBD onset.

METHOD

We recruited 157 PD, 16 isolated RBD (iRBD), and 78 healthy controls. PD patients were identified as (1) PD with RBD preceding motor symptoms (PD-preRBD, n = 50), (2) PD with RBD posterior to motor symptoms (PD-postRBD, n = 31), (3) PD without RBD (PD-nonRBD, n = 75). The volumes of crucial brain regions, including the basal ganglia and limbic structures in T1-weighted imaging, and the contrast-noise-ratios of locus coeruleus (LC) and substantia nigra (SN) in neuromelanin-sensitive magnetic resonance imaging, were extracted. To simulate the sequence of disease progression for cross-sectional data, an event-based model was introduced to estimate the maximum likelihood sequence of regions' involvement for each group. Then, a statistical parameter, the Bhattacharya coefficient (BC), was used to evaluate the similarity of the sequence.

RESULTS

The model predicted that SN occupied the highest likelihood in the maximum likelihood sequence of disease progression in the all PD subgroups, while LC was specifically positioned earlier to SN in iRBD, a prodromal phase of PD. Subsequent early involvement of LC was observed in the both PD-preRBD and PD-postRBD. In contrast, atrophy in the para-hippocampal gyrus but relatively intact LC in the early stage was demonstrated in PD-nonRBD. Then, the similarity comparisons indicated higher BC between PD-postRBD and PD-preRBD (BC = 0.76) but lower BC between PD-postRBD and PD-nonRBD group (BC = 0.41). iRBD had higher BC against PD-preRBD (BC = 0.66) and PD-postRBD (BC = 0.63) but lower BC against PD- nonRBD (BC = 0.48).

CONCLUSION

The spatiotemporal sequence of neurodegeneration between PD-pre and PD-post were similar but distinct from PD-nonRBD. The presence of RBD may be the essential factor for differentiating the degeneration patterns of PD, but the timing of RBD onset has currently proved to be not.