The functional brain connectome in isolated rapid eye movement sleep behavior disorder and Parkinson's disease

BACKGROUND

Isolated rapid-eye-movement behavior disorder (iRBD) often precedes the development of alpha-synucleinopathies such as Parkinson's disease (PD). Magnetic resonance imaging (MRI) studies have revealed structural brain alterations in iRBD partially resembling those observed in PD. However, relatively little is known about whole-brain functional brain alterations in iRBD. Here, we characterize the functional brain connectome of iRBD compared with PD patients and healthy controls (HC) using resting-state functional MRI (rs-fMRI).

METHODS

Eighteen iRBD subjects (67.3 ± 6.6 years), 18 subjects with PD (65.4 ± 5.8 years), and 39 age- and sex-matched HC (64.4 ± 9.2 years) underwent rs-fMRI at 3 T. We applied a graph theoretical approach to analyze the brain functional connectome at the global and regional levels. Data were analyzed using both frequentist and Bayesian statistics.

RESULTS

Global connectivity was largely preserved in iRBD and PD individuals. In contrast, both disease groups displayed altered local connectivity mainly in the motor network, temporal cortical regions including the limbic system, and the visual system. There were some group specific alterations, and connectivity changes were pronounced in PD individuals. Overall, however, there was a good agreement of the connectome changes observed in both disease groups.

CONCLUSIONS

This study provides evidence for widespread functional brain connectivity alterations in iRBD, including motor circuitry, despite normal motor function. Connectome alterations showed substantial resemblance with those observed in PD, underlining a close pathophysiological relationship of iRBD and PD.

Investigating the aspect of asymmetry in brain-first versus body-first Parkinson's disease

Parkinson's disease (PD) is characterized by a progressive loss of dopaminergic neurons in the substantia nigra. Recent literature has proposed two subgroups of PD. The "body-first subtype" is associated with a prodrome of isolated REM-sleep Behavior Disorder (iRBD) and a relatively symmetric brain degeneration. The "brain-first subtype" is suggested to have a more asymmetric degeneration and a prodromal stage without RBD. This study aims to investigate the proposed difference in symmetry of the degeneration pattern in the presumed body and brain-first PD subtypes. We analyzed 123I-FP-CIT (DAT SPECT) and 18F-FDG PET brain imaging in three groups of patients (iRBD, n = 20, de novo PD with prodromal RBD, n = 22, and de novo PD without RBD, n = 16) and evaluated dopaminergic and glucose metabolic symmetry. The RBD status of all patients was confirmed with video-polysomnography. The PD groups did not differ from each other with regard to the relative or absolute asymmetry of DAT uptake in the putamen (p = 1.0 and p = 0.4, respectively). The patient groups also did not differ from each other with regard to the symmetry of expression of the PD-related metabolic pattern (PDRP) in each hemisphere. The PD groups had no difference in symmetry considering mean FDG uptake in left and right regions of interest and generally had the same degree of symmetry as controls, while the iRBD patients had nine regions with abnormal left-right differences (p < 0.001). Our findings do not support the asymmetry aspect of the "body-first" versus "brain-first" hypothesis.

Spoken Language Alterations can Predict Phenoconversion in Isolated Rapid Eye Movement Sleep Behavior Disorder: A Multicenter Study

OBJECTIVE

This study assessed the relationship between speech and language impairment and outcome in a multicenter cohort of isolated/idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD).

METHODS

Patients with iRBD from 7 centers speaking Czech, English, German, French, and Italian languages underwent a detailed speech assessment at baseline. Story-tale narratives were transcribed and linguistically annotated using fully automated methods based on automatic speech recognition and natural language processing algorithms, leading to the 3 distinctive linguistic and 2 acoustic patterns of language deterioration and associated composite indexes of their overall severity. Patients were then prospectively followed and received assessments for parkinsonism or dementia during follow-up. The Cox proportional hazard was performed to evaluate the predictive value of language patterns for phenoconversion over a follow-up period of 5 years.

RESULTS

Of 180 patients free of parkinsonism or dementia, 156 provided follow-up information. After a mean follow-up of 2.7 years, 42 (26.9%) patients developed neurodegenerative disease. Patients with higher severity of linguistic abnormalities (hazard ratio [HR = 2.35]) and acoustic abnormalities (HR = 1.92) were more likely to develop a defined neurodegenerative disease, with converters having lower content richness (HR = 1.74), slower articulation rate (HR = 1.58), and prolonged pauses (HR = 1.46). Dementia-first (n = 16) and parkinsonism-first with mild cognitive impairment (n = 9) converters had higher severity of linguistic abnormalities than parkinsonism-first with normal cognition converters (n = 17).

INTERPRETATION

Automated language analysis might provide a predictor of phenoconversion from iRBD into synucleinopathy subtypes with cognitive impairment, and thus can be used to stratify patients for neuroprotective trials. ANN NEUROL 2024;95:530-543.

Undiagnosed obstructive sleep apnea syndrome as a treatable cause of new-onset sleepiness in some post-COVID patients

BACKGROUND AND PURPOSE

Infection with COVID-19 can lead to persistent sequelae, such as fatigue, daytime sleepiness or disturbed sleep, that can remain for more than 12 weeks and that are summarized as post-COVID syndrome. The causes remain unclear. The present study investigated the presence of sleep disorders in patients with post-COVID syndrome using polysomnography.

METHODS

Thirty-four patients with post-COVID syndrome and new-onset fatigue and sleepiness after a SARS-CoV2 infection underwent polysomnography in accordance with American Association of Sleep Medicine (AASM) standards as part of their clinical workup. Analysis was performed visually based on AASM criteria (scoring manual version 2.6, 2020).

RESULTS

Polysomnography revealed a sleep efficiency of <80% in 50% of patients and a mean respiratory disturbance index (RDI) of 9.9 ± 15.4/h. Excluding central apneas, 12 patients (35%) had an RDI of ≥5/h, pointing to obstructive sleep apnea syndrome (OSAS; AASM 2014). Patients with a high RDI were significantly older (p = 0.01) and showed a trend towards a higher body mass index (p = 0.08) than patients with a normal RDI but had no other risk factors for OSAS. Six patients agreed to long-term treatment of their OSAS and all reported discontinuation of daytime symptoms.

CONCLUSIONS

Post-COVID symptoms such as daytime sleepiness, fatigue and memory and concentration problems may in part be a result of reduced sleep efficiency and sleep apnea in a relevant percentage of patients. This possibly treatable cause of the symptoms should be kept in mind in patients presenting with post-COVID syndrome.

Neuronally Derived Extracellular Vesicle α-Synuclein as a Serum Biomarker for Individuals at Risk of Developing Parkinson Disease

IMPORTANCE

Nonmotor symptoms of Parkinson disease (PD) often predate the movement disorder by decades. Currently, there is no blood biomarker to define this prodromal phase.

OBJECTIVE

To investigate whether α-synuclein in neuronally derived serum-extracellular vesicles identifies individuals at risk of developing PD and related dementia.

DESIGN, SETTING, and PARTICIPANTS

This retrospective, cross-sectional multicenter study of serum samples included the Oxford Discovery, Marburg, Cologne, and Parkinson's Progression Markers Initiative cohorts. Participants were recruited from July 2013 through August 2023 and samples were analyzed from April 2022 through September 2023. The derivation group (n = 170) included participants with isolated rapid eye movement sleep behavior disorder (iRBD) and controls. Two validation groups were used: the first (n = 122) included participants with iRBD and controls and the second (n = 263) included nonmanifest GBA1N409S gene carriers, participants with iRBD or hyposmia, and available dopamine transporter single-photon emission computed tomography, healthy controls, and patients with sporadic PD. Overall the study included 199 participants with iRBD, 20 hyposmic participants with available dopamine transporter single-photon emission computed tomography, 146 nonmanifest GBA1N409S gene carriers, 21 GBA1N409S gene carrier patients with PD, 50 patients with sporadic PD, and 140 healthy controls. In the derivation group and validation group 1, participants with polysomnographically confirmed iRBD were included. In the validation group 2, at-risk participants with available Movement Disorder Society prodromal markers and serum samples were included. Among 580 potential participants, 4 were excluded due to alternative diagnoses.

EXPOSURES

Clinical assessments, imaging, and serum collection.

MAIN OUTCOME AND MEASURES

L1CAM-positive extracellular vesicles (L1EV) were immunocaptured from serum. α-Synuclein and syntenin-1 were measured by electrochemiluminescence. Area under the receiver operating characteristic (ROC) curve (AUC) with 95% CIs evaluated biomarker performance. Probable prodromal PD was determined using the updated Movement Disorder Society research criteria. Multiple linear regression models assessed the association between L1EV α-synuclein and prodromal markers.

RESULTS

Among 576 participants included, the mean (SD) age was 64.30 (8.27) years, 394 were male (68.4%), and 182 were female (31.6%). A derived threshold of serum L1EV α-synuclein distinguished participants with iRBD from controls (AUC = 0.91; 95% CI, 0.86-0.96) and those with more than 80% probability of having prodromal PD from participants with less than 5% probability (AUC = 0.80; 95% CI, 0.71-0.89). Subgroup analyses revealed that specific combinations of prodromal markers were associated with increased L1EV α-synuclein levels. Across all cohorts, L1EV α-synuclein differentiated participants with more than 80% probability of having prodromal PD from current and historic healthy control populations (AUC = 0.90; 95% CI, 0.87-0.93), irrespective of initial diagnosis. L1EV α-synuclein was increased in at-risk participants with a positive cerebrospinal fluid seed amplification assay and was above the identified threshold in 80% of cases (n = 40) that phenoconverted to PD or related dementia.

CONCLUSIONS AND RELEVANCE

L1EV α-synuclein in combination with prodromal markers should be considered in the stratification of those at high risk of developing PD and related Lewy body diseases.

Reduced Gastric Contraction in Rapid-Eye-Movement Sleep Behavior Disorder and De Novo Parkinson's Disease

BACKGROUND

Reduced gastric motility in Parkinson's disease (PD) has been reported, but hardly any study exists in subjects with isolated rapid-eye-movement (REM) sleep behavior disorder (iRBD), a specific prodrome of α-synucleinopathies.

OBJECTIVES

We compared the gastric motility of 17 iRBD subjects with that of 18 PD subjects (15 drug naive, 3 early treated in defined off) and 15 healthy controls (HC) with real-time magnetic resonance imaging (rtMRI).

METHODS

After overnight fasting, participants consumed a standardized breakfast and underwent a 3-T rtMRI of the stomach. Amplitude and velocity of the peristaltic waves were analyzed under blinded conditions. Gastric motility index (GMI) was calculated. The procedure was repeated in 12 of 17 iRBD subjects ~2.5 years later. Nine of these 12 iRBD subjects were hyposmic.

RESULTS

In iRBD and PD subjects the amplitude of the peristaltic waves was significantly reduced compared with HCs (iRBD vs. HC: 8.7 ± 3.7 vs. 11.9 ± 4.1 mm, P = 0.0097; PD vs. HC: 6.8 ± 2.2 vs. 11.9 ± 4.1 mm, P = 0.0001). The amplitude in iRBD and PD subjects was decreased to the same extent. The GMI was reduced in only PD subjects (PD vs. HC: P = 0.0027; PD vs. iRBD: P = 0.0203). After ~2.5 years the amplitude in iRBD subjects did not significantly decrease further.

CONCLUSION

The amplitude of the peristaltic waves was markedly reduced in iRBD, a prodrome of α-synucleinopathies. This reduction was similar to the extent observed already in manifest early PD. This finding implies that the α-synuclein pathology affects the innervation of the stomach already in the prodromal stage. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Occipital hypometabolism is a risk factor for conversion to Parkinson's disease in isolated REM sleep behaviour disorder

PURPOSE

Isolated REM sleep behaviour disorder (iRBD) patients are at high risk of developing clinical syndromes of the α-synuclein spectrum. Progression markers are needed to determine the neurodegenerative changes and to predict their conversion. Brain imaging with 18F-FDG PET in iRBD is promising, but longitudinal studies are scarce. We investigated the regional brain changes in iRBD over time, related to phenoconversion.

METHODS

Twenty iRBD patients underwent two consecutive 18F-FDG PET brain scans and clinical assessments (3.7 ± 0.6 years apart). Seventeen patients also underwent 123I-MIBG and 123I-FP-CIT SPECT scans at baseline. Four subjects phenoconverted to Parkinson's disease (PD) during follow-up. 18F-FDG PET scans were compared to controls with a voxel-wise single-subject procedure. The relationship between regional brain changes in metabolism and PD-related pattern scores (PDRP) was investigated.

RESULTS

Individual hypometabolism t-maps revealed three scenarios: (1) normal 18F-FDG PET scans at baseline and follow-up (N = 10); (2) normal scans at baseline but occipital or occipito-parietal hypometabolism at follow-up (N = 4); (3) occipital hypometabolism at baseline and follow-up (N = 6). All patients in the last group had pathological 123I-MIBG and 123I-FP-CIT SPECT. iRBD converters (N = 4) showed occipital hypometabolism at baseline (third scenario). At the group level, hypometabolism in the frontal and occipito-parietal regions and hypermetabolism in the cerebellum and limbic regions were progressive over time. PDRP z-scores increased over time (0.54 ± 0.36 per year). PDRP expression was driven by occipital hypometabolism and cerebellar hypermetabolism.

CONCLUSIONS

Our results suggest that occipital hypometabolism at baseline in iRBD implies a short-term conversion to PD. This might help in stratification strategies for disease-modifying trials.

HLA in isolated REM sleep behavior disorder and Lewy body dementia

Synucleinopathies-related disorders such as Lewy body dementia (LBD) and isolated/idiopathic REM sleep behavior disorder (iRBD) have been associated with neuroinflammation. In this study, we examined whether the human leukocyte antigen (HLA) locus plays a role in iRBD and LBD. In iRBD, HLA-DRB1*11:01 was the only allele passing FDR correction (OR = 1.57, 95% CI = 1.27-1.93, p = 2.70e-05). We also discovered associations between iRBD and HLA-DRB1 70D (OR = 1.26, 95%CI = 1.12-1.41, p = 8.76e-05), 70Q (OR = 0.81, 95%CI = 0.72-0.91, p = 3.65e-04) and 71R (OR = 1.21, 95%CI = 1.08-1.35, p = 1.35e-03). Position 71 (pomnibus  = 0.00102) and 70 (pomnibus  = 0.00125) were associated with iRBD. Our results suggest that the HLA locus may have different roles across synucleinopathies.

Dermal Real-Time Quaking-Induced Conversion Is a Sensitive Marker to Confirm Isolated Rapid Eye Movement Sleep Behavior Disorder as an Early α-Synucleinopathy

BACKGROUND

Skin biopsy is a potential tool for the premortem confirmation of an α-synucleinopathy.

OBJECTIVE

The aim was to assess the aggregation assay real-time quaking-induced conversion (RT-QuIC) of skin biopsy lysates to confirm isolated rapid eye movement sleep behavior disorder (iRBD) as an α-synucleinopathy.

METHODS

Skin biopsies of patients with iRBD, Parkinson's disease (PD), and controls were analyzed using RT-QuIC and immunohistochemical detection of phospho-α-synuclein.

RESULTS

α-Synuclein aggregation was detected in 97.4% of iRBD patients (78.4% of iRBD biopsies), 87.2% of PD patients (70% of PD biopsies), and 13% of controls (7.9% of control biopsies), with a higher seeding activity in iRBD compared to PD. RT-QuIC was more sensitive but less specific than immunohistochemistry.

CONCLUSIONS

Dermal RT-QuIC is a sensitive method to detect α-synuclein aggregation in iRBD, and high seeding activity may indicate a strong involvement of dermal nerve fibers in these patients. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

HLA in isolated REM sleep behavior disorder and Lewy body dementia

Background and Objectives

Isolated/idiopathic REM sleep behavior disorder (iRBD) and Lewy body dementia (LBD) are synucleinopathies that have partial genetic overlap with Parkinson's disease (PD). Previous studies have shown that neuroinflammation plays a substantial role in these disorders. In PD, specific residues of the human leukocyte antigen ( HLA ) were suggested to be associated with a protective effect. This study examined whether the HLA locus plays a similar role in iRBD, LBD and PD.

Methods

We performed HLA imputation on iRBD genotyping data (1,072 patients and 9,505 controls) and LBD whole-genome sequencing (2,604 patients and 4,032 controls) using the multi-ethnic HLA reference panel v2 from the Michigan Imputation Server. Using logistic regression, we tested the association of HLA alleles, amino acids and haplotypes with disease susceptibility. We included age, sex and the top 10 principal components as covariates. We also performed an omnibus test to examine which HLA residue positions explain the most variance.

Results

In iRBD, HLA-DRB1 *11:01 was the only allele passing FDR correction (OR=1.57, 95% CI=1.27-1.93, p =2.70e-05). We also discovered associations between iRBD and HLA-DRB1 70D (OR=1.26, 95%CI=1.12-1.41, p =8.76e-05), 70Q (OR=0.81, 95% CI=0.72-0.91, p =3.65e-04) and 71R (OR=1.21, 95% CI=1.08-1.35, p =1.35e-03). In HLA-DRB1 , position 71 ( p omnibus =0.00102) and 70 ( p omnibus =0.00125) were associated with iRBD. We found no association in LBD.

Discussion

This study identified an association between HLA-DRB1 11:01 and iRBD, distinct from the previously reported association in PD. Therefore, the HLA locus may play different roles across synucleinopathies. Additional studies are required better to understand HLA's role in iRBD and LBD.

Progression of clinical markers in prodromal Parkinson's disease and dementia with Lewy bodies: a multicentre study

The neurodegenerative synucleinopathies, including Parkinson's disease and dementia with Lewy bodies, are characterized by a typically lengthy prodromal period of progressive subclinical motor and non-motor manifestations. Among these, idiopathic REM sleep behavior disorder (iRBD) is a powerful early predictor of eventual phenoconversion, and therefore represents a critical opportunity to intervene with neuroprotective therapy. To inform the design of randomized trials, it is essential to study the natural progression of clinical markers during the prodromal stages of disease in order to establish optimal clinical endpoints. In this study, we combined prospective follow-up data from 28 centers of the International REM Sleep Behavior Disorder Study Group representing 12 countries. Polysomnogram-confirmed REM sleep behavior disorder subjects were assessed for prodromal Parkinson's disease using the Movement Disorder Society criteria and underwent periodic structured sleep, motor, cognitive, autonomic and olfactory testing. We used linear mixed-effect modelling to estimate annual rates of clinical marker progression stratified by disease subtype, including prodromal Parkinson's disease and prodromal dementia with Lewy bodies. In addition, we calculated sample size requirements to demonstrate slowing of progression under different anticipated treatment effects. Overall, 1160 subjects were followed over an average of 3.3 ± 2.2 years. Among clinical variables assessed continuously, motor variables tended to progress faster and required the lowest sample sizes, ranging from 151-560 per group (at 50% drug efficacy and 2-year follow-up). By contrast, cognitive, olfactory, and autonomic variables showed modest progression with higher variability, resulting in high sample sizes. The most efficient design was a time-to-event analysis using combined milestones of motor and cognitive decline, estimating 117 per group at 50% drug efficacy and 2-year trial duration. Finally, while phenoconverters showed overall greater progression than non-converters in motor, olfactory, cognitive, and certain autonomic markers, the only robust difference in progression between Parkinson's disease and dementia with Lewy bodies phenoconverters was in cognitive testing. This large multicenter study demonstrates the evolution of motor and non-motor manifestations in prodromal synucleinopathy. These findings provide optimized clinical endpoints and sample size estimates to inform future neuroprotective trials.

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.

FDG-PET combined with learning vector quantization allows classification of neurodegenerative diseases and reveals the trajectory of idiopathic REM sleep behavior disorder

BACKGROUND AND OBJECTIVES

¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) combined with principal component analysis (PCA) has been applied to identify disease-related brain patterns in neurodegenerative disorders such as Parkinson's disease (PD), Dementia with Lewy Bodies (DLB) and Alzheimer's disease (AD). These patterns are used to quantify functional brain changes at the single subject level. This is especially relevant in determining disease progression in idiopathic REM sleep behavior disorder (iRBD), a prodromal stage of PD and DLB. However, the PCA method is limited in discriminating between neurodegenerative conditions. More advanced machine learning algorithms may provide a solution. In this study, we apply Generalized Matrix Learning Vector Quantization (GMLVQ) to FDG-PET scans of healthy controls, and patients with AD, PD and DLB. Scans of iRBD patients, scanned twice with an approximate 4 year interval, were projected into GMLVQ space to visualize their trajectory.

METHODS

We applied a combination of SSM/PCA and GMLVQ as a classifier on FDG-PET data of healthy controls, AD, DLB, and PD patients. We determined the diagnostic performance by performing a ten times repeated ten fold cross validation. We analyzed the validity of the classification system by inspecting the GMLVQ space. First by the projection of the patients into this space. Second by representing the axis, that span this decision space, into a voxel map. Furthermore, we projected a cohort of RBD patients, whom have been scanned twice (approximately 4 years apart), into the same decision space and visualized their trajectories.

RESULTS

The GMLVQ prototypes, relevance diagonal, and decision space voxel maps showed metabolic patterns that agree with previously identified disease-related brain patterns. The GMLVQ decision space showed a plausible quantification of FDG-PET data. Distance traveled by iRBD subjects through GMLVQ space per year (i.e. velocity) was correlated with the change in motor symptoms per year (Spearman's rho =0.62, P=0.004).

CONCLUSION

In this proof-of-concept study, we show that GMLVQ provides a classification of patients with neurodegenerative disorders, and may be useful in future studies investigating speed of progression in prodromal disease stages.

Progressive Olfactory Impairment and Cardiac Sympathetic Denervation in REM Sleep Behavior Disorder

Background:

Isolated rapid eye movement sleep behavior disorder (iRBD) is prodromal for Parkinson’s disease (PD) and dementia with Lewy bodies (DLB).

Objective:

We investigated the use of cardiac [¹²³I]meta-iodo-benzyl-guanidine scintigraphy ([¹²³I]MIBG) and olfactory testing— in comparison to [¹²³I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane single photon emission computed tomography ([¹²³I]FP-CIT-SPECT)— for identifying iRBD patients as prodromal phenotype of PD/DLB.

Methods:

37 RBD subjects underwent cardiac [¹²³I]MIBG and brain [¹²³I]FP-CIT-SPECT at baseline. Olfactory (Sniffin’ Sticks), cognitive and motor functions were tested annually for ∼4 years.

Results:

29/37 (78.4%) subjects had a pathological [¹²³I]MIBG, of whom 86.2% (25/29) presented at least a moderate hyposmia at baseline (threshold/discrimination/identification-(TDI-)score ≤25). 20/37 (54.1%) subjects had a pathological [¹²³I]FP-CIT-SPECT, always combined with a pathological [¹²³I]MIBG. In subjects with pathological [¹²³I]MIBG, olfactory function worsened (mainly due to threshold and discrimination subscores) from baseline to follow-up (p = 0.005). Olfaction was more impaired in subjects with pathological [¹²³I]MIBG compared to those with normal [¹²³I]MIBG at baseline (p = 0.001) and follow-up (p < 0.001). UPDRS-III scores increased in subjects with both pathological [¹²³I]MIBG and [¹²³I]FP-CIT-SPECT. In this group, seven subjects phenoconverted to PD, all— except for one— presented with at least moderate hyposmia at baseline.

Conclusion:

A combination of the biomarkers “pathological [¹²³I]MIBG” and “hyposmia” likely identifies iRBD patients in an early prodromal stage of PD/DLB, i.e., before nigrostriatal degeneration is visualized. One-third of the subjects with pathological [¹²³I]MIBG had a normal [¹²³I]FP-CIT-SPECT. Noteworthy, in iRBD subjects with pathological [¹²³I]MIBG, olfactory impairment is progressive independent of the [¹²³I]FP-CIT-SPECT status.

Rare PSAP Variants and Possible Interaction with GBA in REM Sleep Behavior Disorder

BACKGROUND

PSAP encodes saposin C, the co-activator of glucocerebrosidase, encoded by GBA. GBA mutations are associated with idiopathic/isolated REM sleep behavior disorder (iRBD), a prodromal stage of synucleinopathy.

OBJECTIVE

To examine the role of PSAP mutations in iRBD.

METHODS

We fully sequenced PSAP and performed Optimized Sequence Kernel Association Test in 1,113 iRBD patients and 2,324 controls. We identified loss-of-function (LoF) mutations, which are very rare in PSAP, in three iRBD patients and none in controls (uncorrected p = 0.018).

RESULTS

Two variants were stop mutations, p.Gln260Ter and p.Glu166Ter, and one was an in-frame deletion, p.332_333del. All three mutations have a deleterious effect on saposin C, based on in silico analysis. In addition, the two carriers of p.Glu166Ter and p.332_333del mutations also carried a GBA variant, p.Arg349Ter and p.Glu326Lys, respectively. The co-occurrence of these extremely rare PSAP LoF mutations in two (0.2%) GBA variant carriers in the iRBD cohort, is unlikely to occur by chance (estimated co-occurrence in the general population based on gnomAD data is 0.00035%). Although none of the three iRBD patients with PSAP LoF mutations have phenoconverted to an overt synucleinopathy at their last follow-up, all manifested initial signs suggestive of motor dysfunction, two were diagnosed with mild cognitive impairment and all showed prodromal clinical markers other than RBD. Their probability of prodromal PD, according to the Movement Disorder Society research criteria, was 98% or more.

CONCLUSION

These results suggest a possible role of PSAP variants in iRBD and potential genetic interaction with GBA, which requires additional studies.

Dysprosody in Isolated REM Sleep Behavior Disorder with Impaired Olfaction but Intact Nigrostriatal Pathway

BACKGROUND

Impairments of olfactory and speech function are likely early prodromal symptoms of α-synucleinopathy.

OBJECTIVE

The aim of this study is to assess whether dysprosody is present in isolated rapid eye movement sleep behavior disorder (iRBD) with hyposmia/anosmia and a normal nigrostriatal system.

METHODS

Pitch variability during speech was investigated in 17 iRBD subjects with normal olfactory function (iRBD-NOF), 30 iRBD subjects with abnormal olfactory function (iRBD-AOF), and 50 healthy controls. iRBD subjects were evaluated using the University of Pennsylvania Smell Identification Test and [123I]-2ß-carbomethoxy-3ß-(4-iodophenyl)-N-(3-fluoropropyl)-nortropane dopamine transporter single-photon emission computed tomography (DAT-SPECT). All iRBD subjects completed the 24-month follow-up with DAT-SPECT, speech, and olfactory testing.

RESULTS

At baseline, only iRBD-AOF showed monopitch when compared to iRBD-NOF (P = 0.04) and controls (P = 0.03), with no difference between iRBD-NOF and controls (P = 1). At follow-up, dysprosody progressed only in iRBD-AOF with abnormal DAT-SPECT (P = 0.03).

CONCLUSION

Prosody is impaired in hyposmic but not in normosmic iRBD subjects before the nigrostriatal dopaminergic transmission is affected (Braak stage 2). © 2021 International Parkinson and Movement Disorder Society.

Rapid Eye Movement Sleep Behavior Disorder: Abnormal Cardiac Image and Progressive Abnormal Metabolic Brain Pattern

BACKGROUND

Isolated rapid eye movement sleep behavior disorder (iRBD) is prodromal for α-synucleinopathies.

OBJECTIVE

The aim of this study was to determine whether pathological cardiac [¹²³ I]meta-iodobenzylguanidine scintigraphy ([¹²³ I]MIBG) is associated with progression of [¹⁸ F]fluorodeoxyglucose-positron emission tomography-based Parkinson's disease (PD)-related brain pattern (PDRP) expression in iRBD.

METHODS

Seventeen subjects with iRBD underwent [¹⁸ F]fluorodeoxyglucose-positron emission tomography brain imaging twice ~3.6 years apart. In addition, [¹²³ I]MIBG and [¹²³ I]N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane single-photon emission computed tomography ([¹²³ I]FP-CIT-SPECT) at baseline were performed. Olfactory, cognitive, and motor functions were tested annually.

RESULTS

Twelve of 17 subjects had pathological [¹²³ I]MIBG. At baseline, 6 of 12 of these expressed the PDRP (suprathreshold PDRP z score). At follow-up, 12 of 17 subjects had suprathreshold PDRP z scores, associated with pathological [¹²³ I]MIBG in 92% and with pathological [¹²³ I]FP-CIT-SPECT in 75%. Subjects with pathological [¹²³ I]MIBG had higher PDRP z score change per year (P = 0.027). Three subjects phenoconverted to PD; all had pathological [¹²³ I]MIBG and [¹²³ I]FP-CIT-SPECT, suprathreshold baseline PDRP z scores, and hyposmia.

CONCLUSIONS

Pathological [¹²³ I]MIBG was associated with progressive and suprathreshold PDRP z scores at follow-up. Abnormal [¹²³ I]MIBG likely identifies iRBD as prodromal PD earlier than pathological [¹²³ I]FP-CIT-SPECT. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

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.

Increased muscle sympathetic nerve activity and impaired baroreflex control in isolated REM-sleep behavior disorder

OBJECTIVE

Changes in baroreflex sensitivity have been reported in patients with idiopathic Parkinson's disease (PD). We sought to investigate the hypothesis that patients with isolated rapid eye movement (REM)-sleep behavior disorder (iRBD), known to be a prodromal stage for PD, will show abnormalities in baroreflex control.

METHODS

Ten iRBD patients were compared to 10 sex- and age-matched healthy controls. Their cardiovascular parameters and muscle sympathetic nerve activity (MSNA) were evaluated at rest and during baroreflex stimulation.

RESULTS

MSNA at rest was higher in iRBD patients (burst frequency [BF]: 44 ± 3 bursts/min; burst incidence [BI]: 60 ± 8 bursts/100 heartbeats) as compared to the controls (BF: 29 ± 3 bursts/min, p < 0.001; BI: 43 ± 9 bursts/100 heartbeats, p < 0.001). During baroreflex stimulation, iRBD patients showed increased absolute values of MSNA (BF: F = 62.728; p < 0.001; BI: F = 16.277; p < 0.001) as compared to the controls. The iRBD patients had decreased diastolic blood pressure at baseline and during lower body negative pressure, but the level of significance was not met.

CONCLUSION

Our study shows increased MSNA and impaired baroreflex control in iRBD patients. We propose that the inhibitory effect of locus coeruleus on baroreflex function might be impaired, leading to the disinhibition of sympathetic outflow.

SIGNIFICANCE

These findings might reflect the destruction of brain areas due to the ascending P-α-synuclein deposits in iRBD patients.

Speech Biomarkers in Rapid Eye Movement Sleep Behavior Disorder and Parkinson Disease

Objective

This multilanguage study used simple speech recording and high‐end pattern analysis to provide sensitive and reliable noninvasive biomarkers of prodromal versus manifest α‐synucleinopathy in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) and early‐stage Parkinson disease (PD).

Methods

We performed a multicenter study across the Czech, English, German, French, and Italian languages at 7 centers in Europe and North America. A total of 448 participants (337 males), including 150 with iRBD (mean duration of iRBD across language groups 0.5–3.4 years), 149 with PD (mean duration of disease across language groups 1.7–2.5 years), and 149 healthy controls were recorded; 350 of the participants completed the 12‐month follow‐up. We developed a fully automated acoustic quantitative assessment approach for the 7 distinctive patterns of hypokinetic dysarthria.

Results

No differences in language that impacted clinical parkinsonian phenotypes were found. Compared with the controls, we found significant abnormalities of an overall acoustic speech severity measure via composite dysarthria index for both iRBD (p = 0.002) and PD (p < 0.001). However, only PD (p < 0.001) was perceptually distinct in a blinded subjective analysis. We found significant group differences between PD and controls for monopitch (p < 0.001), prolonged pauses (p < 0.001), and imprecise consonants (p = 0.03); only monopitch was able to differentiate iRBD patients from controls (p = 0.004). At the 12‐month follow‐up, a slight progression of overall acoustic speech impairment was noted for the iRBD (p = 0.04) and PD (p = 0.03) groups.

Interpretation

Automated speech analysis might provide a useful additional biomarker of parkinsonism for the assessment of disease progression and therapeutic interventions. ANN NEUROL 2021;90:62–75

Convergent patterns of structural brain changes in rapid eye movement sleep behavior disorder and Parkinson's disease on behalf of the German rapid eye movement sleep behavior disorder study group

STUDY OBJECTIVES

Rapid eye movement sleep behavior disorder (RBD) is considered a prodromal state of Parkinson's disease (PD). We aimed to characterize patterns of structural brain changes in RBD and PD patients using multimodal MRI.

METHODS

A total of 30 patients with isolated RBD, 29 patients with PD, and 56 age-matched healthy controls (HC) underwent MRI at 3T, including tensor-based morphometry, diffusion tensor imaging, and assessment of cortical thickness.

RESULTS

RBD individuals showed increased volume of the right caudate nucleus compared with HC, and higher cerebellar volume compared with both PD subjects and HC. Similar to PD subjects, RBD patients displayed increased fractional anisotropy (FA) in the corticospinal tracts, several tracts mainly related to non-motor function, and reduced FA of the corpus callosum compared with HC. Further, RBD subjects showed higher FA in the cerebellar peduncles and brainstem compared with both, PD patients and HC. PD individuals exhibited lower than normal volume in the basal ganglia, midbrain, pedunculopontine nuclei, and cerebellum. In contrast, volume in PD subjects was increased in the thalamus compared with both HC and RBD subjects.

CONCLUSIONS

We found convergent patterns of structural brain alterations in RBD and PD patients compared with HC. The changes observed suggest a co-occurrence of neurodegeneration and compensatory mechanisms that fail with emerging PD pathology. Our findings strengthen the hypothesis of RBD and PD constituting a continuous disease spectrum.

Consistent skin α-synuclein positivity in REM sleep behavior disorder - A two center two-to-four-year follow-up study

OBJECTIVE/METHODS

Phosphorylated alpha-synuclein (p-syn) in dermal nerves of patients with isolated REM sleep behavior disorder (iRBD) is detectable by immunofluorescence-labeling. Skin-biopsy-p-syn-positivity was recently postulated to be a prodromal marker of Parkinson's disease (PD) or related synucleinopathies. Here, we provide two-to four-year clinical and skin biopsy follow-up data of 33 iRBD patients, whose skin biopsy findings at baseline were reported in 2017.

RESULTS

Follow-up biopsies were available from 25 patients (18 positive at baseline) and showed consistent findings over time in 24 patients. One patient converted from skin-biopsy-negativity to -positivity. P-syn-positivity was observed in iRBD patients who still had a normal FP-CIT-SPECT two years later. Clinically, five of the 23 at baseline skin-biopsy-positive patients (21.7%) had converted to PD or dementia with Lewy bodies at follow-up, but none of the skin-biopsy-negative patients.

CONCLUSIONS

Dermal p-syn in iRBD is most probably an early consistent marker of synucleinopathy and may support other indicators of conversion to manifest disease state.

Saccade, Pupil, and Blink Responses in Rapid Eye Movement Sleep Behavior Disorder

Background

Parkinson's disease (PD) patients exhibit deficits in saccade performance, pupil function, and blink rate. Isolated REM (rapid eye movement) Sleep Behavior Disorder (RBD) is a harbinger to PD making them candidates to investigate for early oculomotor abnormalities as PD biomarkers.

Objectives

We tested whether saccade, pupillary, and blink responses in RBD were similar to PD.

Methods

RBD (n = 22), PD (n = 22) patients, and healthy controls (CTRL) (n = 74) were studied with video‐based eye‐tracking.

Results

RBD patients did not have significantly different saccadic behavior compared to CTRL, but PD patients differed from CTRL and RBD. Both patient groups had significantly lower blink rates, dampened pupil constriction, and dilation responses compared to CTRL.

Conclusion

RBD and PD patients had altered pupil and blink behavior compared to CTRL. Because RBD saccade parameters were comparable to CTRL, pupil and blink brain areas may be impacted before saccadic control areas, making them potential prodromal PD biomarkers. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Novel Associations of BST1 and LAMP3 With REM Sleep Behavior Disorder

OBJECTIVE

To examine the role of genes identified through genome-wide association studies (GWASs) of Parkinson disease (PD) in the risk of isolated REM sleep behavior disorder (iRBD).

METHODS

We fully sequenced 25 genes previously identified in GWASs of PD in a total of 1,039 patients with iRBD and 1,852 controls. The role of rare heterozygous variants in these genes was examined with burden tests. The contribution of biallelic variants was further tested. To examine the potential effect of rare nonsynonymous BST1 variants on the protein structure, we performed in silico structural analysis. Finally, we examined the association of common variants using logistic regression adjusted for age and sex.

RESULTS

We found an association between rare heterozygous nonsynonymous variants in BST1 and iRBD (p = 0.0003 at coverage >50× and 0.0004 at >30×), driven mainly by 3 nonsynonymous variants (p.V85M, p.I101V, and p.V272M) found in 22 (1.2%) controls vs 2 (0.2%) patients. All 3 variants seem to be loss-of-function variants with a potential effect on the protein structure and stability. Rare noncoding heterozygous variants in LAMP3 were also associated with iRBD (p = 0.0006 at >30×). We found no association between rare heterozygous variants in the rest of genes and iRBD. Several carriers of biallelic variants were identified, yet there was no overrepresentation in iRBD.

CONCLUSION

Our results suggest that rare coding variants in BST1 and rare noncoding variants in LAMP3 are associated with iRBD. Additional studies are required to replicate these results and to examine whether loss of function of BST1 could be a therapeutic target.

Olfactory Testing in Parkinson Disease and REM Behavior Disorder: A Machine Learning Approach

OBJECTIVE

We sought to identify an abbreviated test of impaired olfaction amenable for use in busy clinical environments in prodromal (isolated REM sleep behavior disorder [iRBD]) and manifest Parkinson disease (PD).

METHODS

Eight hundred ninety individuals with PD and 313 controls in the Discovery cohort study underwent Sniffin' Stick odor identification assessment. Random forests were initially trained to distinguish individuals with poor (functional anosmia/hyposmia) and good (normosmia/super-smeller) smell ability using all 16 Sniffin' Sticks. Models were retrained using the top 3 sticks ranked by order of predictor importance. One randomly selected 3-stick model was tested in a second independent PD dataset (n = 452) and in 2 iRBD datasets (Discovery n = 241, Marburg n = 37) before being compared to previously described abbreviated Sniffin' Stick combinations.

RESULTS

In differentiating poor from good smell ability, the overall area under the curve (AUC) value associated with the top 3 sticks (anise/licorice/banana) was 0.95 in the Development dataset (sensitivity 90%, specificity 92%, positive predictive value 92%, negative predictive value 90%). Internal and external validation confirmed AUCs ≥0.90. The combination of the 3-stick model determined poor smell, and an RBD screening questionnaire score of ≥5 separated those with iRBD from controls with a sensitivity, specificity, positive predictive value, and negative predictive value of 65%, 100%, 100%, and 30%.

CONCLUSIONS

Our 3-Sniffin'-Stick model holds potential utility as a brief screening test in the stratification of individuals with PD and iRBD according to olfactory dysfunction.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that a 3-Sniffin'-Stick model distinguishes individuals with poor and good smell ability and can be used to screen for individuals with iRBD.

Comprehensive Analysis of Familial Parkinsonism Genes in Rapid-Eye-Movement Sleep Behavior Disorder

BACKGROUND

There is only partial overlap in the genetic background of isolated rapid-eye-movement sleep behavior disorder (iRBD) and Parkinson's disease (PD).

OBJECTIVE

To examine the role of autosomal dominant and recessive PD or atypical parkinsonism genes in the risk of iRBD.

METHODS

Ten genes, comprising the recessive genes PRKN, DJ-1 (PARK7), PINK1, VPS13C, ATP13A2, FBXO7, and PLA2G6 and the dominant genes LRRK2, GCH1, and VPS35, were fully sequenced in 1039 iRBD patients and 1852 controls of European ancestry, followed by association tests.

RESULTS

We found no association between rare heterozygous variants in the tested genes and risk of iRBD. Several homozygous and compound heterozygous carriers were identified, yet there was no overrepresentation in iRBD patients versus controls.

CONCLUSION

Our results do not support a major role for variants in these genes in the risk of iRBD. © 2020 International Parkinson and Movement Disorder Society.

Four-Year Follow-up of [18 F]Fluorodeoxyglucose Positron Emission Tomography-Based Parkinson's Disease-Related Pattern Expression in 20 Patients with Isolated Rapid Eye Movement Sleep Behavior Disorder Shows Prodromal Progression

Background

Isolated rapid eye movement sleep behavior disorder is known to be prodromal for alpha‐synucleinopathies, such as Parkinson's disease (PD) and dementia with Lewy bodies. The [¹⁸F]fluorodeoxyglucose‐positron emission tomography (PET)–based PD‐related brain pattern can be used to monitor disease progression.

Objective

We longitudinally investigated PD‐related brain pattern expression changes in 20 subjects with isolated rapid eye movement sleep behavior disorder to investigate whether this may be a suitable technique to study prodromal PD progression in these patients and to identify potential phenoconverters.

Methods

Subjects underwent two [¹⁸F]fluorodeoxyglucose‐PET brain scans ~3.7 years apart, along with baseline and repeated motor, cognitive, and olfactory testing within roughly the same time frame.

Results

At baseline, 8 of 20 (40%) subjects significantly expressed the PD‐related brain pattern (with z scores above the receiver operating characteristic–determined threshold). At follow‐up, six additional subjects exhibited significant PD‐related brain pattern expression (70% in total). PD‐related brain pattern expression increased in all subjects (P = 0.00008). Four subjects (20%), all with significant baseline PD‐related brain pattern expression, phenoconverted to clinical PD.

Conclusions

Suprathreshold PD‐related brain pattern expression and greater score rate of change may signify greater shorter‐term risk for phenoconversion. Our results support the use of serial PD‐related brain pattern expression measurements as a prodromal PD progression biomarker in patients with isolated rapid eye movement sleep behavior disorder. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Brain Glucose Metabolism Heterogeneity in Idiopathic REM Sleep Behavior Disorder and in Parkinson's Disease

BACKGROUND/OBJECTIVE

Idiopathic REM sleep behavior disorder (iRBD) often precedes Parkinson's disease (PD) and other alpha-synucleinopathies. The aim of the study is to investigate brain glucose metabolism of patients with RBD and PD by means of a multidimensional scaling approach, using18F-FDG-PET as a biomarker of synaptic function.

METHODS

Thirty-six iRBD patients (64.1±6.5 y, 32 M), 72 PD patients, and 79 controls (65.6±9.4 y, 53 M) underwent brain 18F-FDG-PET. PD patients were divided according to the absence (PD, 32 subjects; 68.4±8.5 y, 15 M) or presence (PDRBD, 40 subjects; 71.8±6.6 y, 29 M) of RBD. 18F-FDG-PET scans were used to independently discriminate subjects belonging to four categories: controls (RBD no, PD no), iRBD (RBD yes, PD no), PD (RBD no, PD yes) and PDRBD (RBD yes, PD yes).

RESULTS

The discriminant analysis was moderately accurate in identifying the correct category. This is because the model mostly confounds iRBD and PD, thus the intermediate classes. Indeed, iRBD, PD and PDRBD were progressively located at increasing distance from controls and are ordered along a single dimension (principal coordinate analysis) indicating the presence of a single flux of variation encompassing both RBD and PD conditions.

CONCLUSION

Data-driven approach to brain 18F-FDG-PET showed only moderate discrimination between iRBD and PD patients, highlighting brain glucose metabolism heterogeneity among such patients. iRBD should be considered as a marker of an ongoing condition that may be picked-up in different stages across patients and thus express different brain imaging features and likely different clinical trajectories.

SMPD1 variants do not have a major role in rapid eye movement sleep behavior disorder

Mutations in the sphingomyelin phosphodiesterase 1 (SMPD1) gene were reported to be associated with Parkinson's disease and dementia with Lewy bodies. In the current study, we aimed to evaluate the role of SMPD1 variants in isolated rapid eye movement sleep behavior disorder (iRBD). SMPD1 and its untranslated regions were sequenced using targeted next-generation sequencing in 959 iRBD patients and 1287 controls from European descent. Our study reports no statistically significant association of SMPD1 variants and iRBD. It is hence unlikely that SMPD1 plays a major role in iRBD.

Risk and predictors of dementia and parkinsonism in idiopathic REM sleep behaviour disorder: a multicentre study

Idiopathic REM sleep behaviour disorder (iRBD) is a powerful early sign of Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. This provides an unprecedented opportunity to directly observe prodromal neurodegenerative states, and potentially intervene with neuroprotective therapy. For future neuroprotective trials, it is essential to accurately estimate phenoconversion rate and identify potential predictors of phenoconversion. This study assessed the neurodegenerative disease risk and predictors of neurodegeneration in a large multicentre cohort of iRBD. We combined prospective follow-up data from 24 centres of the International RBD Study Group. At baseline, patients with polysomnographically-confirmed iRBD without parkinsonism or dementia underwent sleep, motor, cognitive, autonomic and special sensory testing. Patients were then prospectively followed, during which risk of dementia and parkinsonsim were assessed. The risk of dementia and parkinsonism was estimated with Kaplan-Meier analysis. Predictors of phenoconversion were assessed with Cox proportional hazards analysis, adjusting for age, sex, and centre. Sample size estimates for disease-modifying trials were calculated using a time-to-event analysis. Overall, 1280 patients were recruited. The average age was 66.3 ± 8.4 and 82.5% were male. Average follow-up was 4.6 years (range = 1-19 years). The overall conversion rate from iRBD to an overt neurodegenerative syndrome was 6.3% per year, with 73.5% converting after 12-year follow-up. The rate of phenoconversion was significantly increased with abnormal quantitative motor testing [hazard ratio (HR) = 3.16], objective motor examination (HR = 3.03), olfactory deficit (HR = 2.62), mild cognitive impairment (HR = 1.91-2.37), erectile dysfunction (HR = 2.13), motor symptoms (HR = 2.11), an abnormal DAT scan (HR = 1.98), colour vision abnormalities (HR = 1.69), constipation (HR = 1.67), REM atonia loss (HR = 1.54), and age (HR = 1.54). There was no significant predictive value of sex, daytime somnolence, insomnia, restless legs syndrome, sleep apnoea, urinary dysfunction, orthostatic symptoms, depression, anxiety, or hyperechogenicity on substantia nigra ultrasound. Among predictive markers, only cognitive variables were different at baseline between those converting to primary dementia versus parkinsonism. Sample size estimates for definitive neuroprotective trials ranged from 142 to 366 patients per arm. This large multicentre study documents the high phenoconversion rate from iRBD to an overt neurodegenerative syndrome. Our findings provide estimates of the relative predictive value of prodromal markers, which can be used to stratify patients for neuroprotective trials.

Abnormal α-synuclein deposits in skin nerves: intra- and inter-laboratory reproducibility

BACKGROUND AND PURPOSE

Visualization of phosphorylated α-synuclein at serine 129 (p-syn) in skin nerves is a promising test for the in vivo diagnosis of synucleinopathies. Here the aim was to establish the intra- and inter-laboratory reproducibility of measurement of intraneural p-syn immunoreactivity in two laboratories with major expertise (Würzburg and Bologna).

METHODS

In total, 43 patients affected by Parkinson's disease (PD 21 patients), dementia with Lewy bodies (DLB 1), rapid eye movement sleep behaviour disorder (RBD 11), multiple system atrophy (MSA-P 4) and small fibre neuropathy (SFN 6) were enrolled. Skin biopsy was performed at the C7 paravertebral spine region and distal skin sites (thigh or leg). The analysis was standardized in both laboratories and carried out blinded on a single skin section double stained with antibodies to p-syn and the pan-axonal marker protein gene product 9.5. Fifty skin sections were randomly selected for the analysis: 25 from C7 and 25 from distal sites. Differently classified sections were re-evaluated to understand the reasons for the discrepancy.

RESULTS

The intra-laboratory analysis showed an excellent reproducibility both in Würzburg (concordance of classification 100% of sections; K = 1; P < 0.001) and Bologna (96% of sections; K = 0.92; P < 0.001). Inter-laboratory analysis showed reproducibility in 45 sections (90%; K = 0.8; P < 0.001) and a different classification in five sections, which was mainly due to fragmented skin samples or weak fluorescent signals.

CONCLUSIONS

Analysis of p-syn showed excellent inter- and intra-laboratory reproducibility supporting the reliability of this technique. The few ascertained discordances were important to further improve the standardization of this technique.

The nasal and gut microbiome in Parkinson's disease and idiopathic rapid eye movement sleep behavior disorder

Background

Increasing evidence connects the gut microbiota and the onset and/or phenotype of Parkinson's disease (PD). Differences in the abundances of specific bacterial taxa have been reported in PD patients. It is, however, unknown whether these differences can be observed in individuals at high risk, for example, with idiopathic rapid eye movement sleep behavior disorder, a prodromal condition of α‐synuclein aggregation disorders including PD.

Objectives

To compare microbiota in carefully preserved nasal wash and stool samples of subjects with idiopathic rapid eye movement sleep behavior disorder, manifest PD, and healthy individuals.

Methods

Microbiota of flash‐frozen stool and nasal wash samples from 76 PD patients, 21 idiopathic rapid eye movement sleep behavior disorder patients, and 78 healthy controls were assessed by 16S and 18S ribosomal RNA amplicon sequencing. Seventy variables, related to demographics, clinical parameters including nonmotor symptoms, and sample processing, were analyzed in relation to microbiome variability and controlled differential analyses were performed.

Results

Differentially abundant gut microbes, such as Akkermansia, were observed in PD, but no strong differences in nasal microbiota. Eighty percent of the differential gut microbes in PD versus healthy controls showed similar trends in idiopathic rapid eye movement sleep behavior disorder, for example, Anaerotruncus and several Bacteroides spp., and correlated with nonmotor symptoms. Metagenomic sequencing of select samples enabled the reconstruction of genomes of so far uncharacterized differentially abundant organisms.

Conclusion

Our study reveals differential abundances of gut microbial taxa in PD and its prodrome idiopathic rapid eye movement sleep behavior disorder in comparison to the healthy controls, and highlights the potential of metagenomics to identify and characterize microbial taxa, which are enriched or depleted in PD and/or idiopathic rapid eye movement sleep behavior disorder. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Underutilization of deep brain stimulation for Parkinson's disease? A survey on possible clinical reasons

BACKGROUND

Only 10% of the up to 15% of patients with advanced Parkinson's disease (PD) eligible for deep brain stimulation (DBS) are referred to specialized centers. This survey evaluated the reasons for the reluctance of patients and referring physicians regarding DBS.

METHODS

Two different questionnaires containing multiple choice and open verbalized questions were developed, one for neurologists and one for patients with PD. The first questionnaire was sent to 87 neurologists in private practice in the catchment area of the authors' medical center, the second to patient support groups in the same region with the help of the German Parkinson Association.

RESULTS

Of the addressed neurologists, 56.3% completed the questionnaire; 61.2% of them estimated the risk of intracerebral hemorrhage as the most severe complication at 4.3% on average; 30.6% were concerned about patients developing mood changes or depression after DBS. Only 16.3% felt unable to care for patients after DBS; 61.2% already had personal experience with patients after DBS and reported good clinical outcome in 90.0% of patients. Although 87.8% claimed to know the specific criteria for DBS, only 40.8% could actively describe them. Only 14.0% could state each of the three main criteria. Of the 46 patients, 88.1% completing the questionnaire had obtained information on DBS from regional patient organizations and 54.8% also from a physician; 44.7% assumed the risk of severe complications to be ≥5.0%. Not being satisfied with their medical treatment was reported by 22.2%, of whom more than 70% considered DBS a further treatment option.

CONCLUSIONS

The latter numbers indicate that treating neurologists tend to overestimate the reluctance of their patients to undergo DBS. Therefore, education of patients and neurologists should be improved and give more realistic figures on the actual outcomes and frequencies of possible complications.

Anesthesiologic regimen and intraoperative delirium in deep brain stimulation surgery for Parkinson's disease

BACKGROUND

In many centers the standard anesthesiological care for deep brain stimulation (DBS) surgery in Parkinson's disease patients is an asleep-awake-asleep procedure. However, sedative drugs and anesthetics can compromise ventilation and hemodynamic stability during the operation and some patients develop a delirious mental state after the initial asleep phase. Further, these drugs interfere with the patient's alertness and cooperativeness, the quality of microelectrode recordings, and the recognition of undesired stimulation effects. In this study, we correlated the incidence of intraoperative delirium with the amount of anesthetics used intraoperatively.

METHODS

The anesthesiologic approach is based on continuous presence and care, avoidance of negative suggestions, use of positive suggestions, and utilization of the patient's own resources. Clinical data from the operations were analyzed retrospectively, the occurrence of intraoperative delirium was extracted from patients' charts. The last 16 patients undergoing the standard conscious sedation procedure (group I) were compared to the first 22 (group II) psychologically-guided patients.

RESULTS

The median amount of propofol decreased from 146 mg (group I) to 0mg (group II), remifentanyl from 0.70 mg to 0.00 mg, respectively (P<0.001 for propofol and remifentanyl). Using the new procedure, 12 of 22 patients (55%) in group II required no anesthetics. Intraoperative delirium was significantly less frequent in group II (P=0.03).

CONCLUSIONS

The occurrence of intraoperative delirium correlates with the amount of intraoperative sedative and anesthetic drugs. Sedation and powerful analgesia are not prerequisites for patients' comfort during awake-DBS-surgery.

Random Whole Body Vibration over 5 Weeks Leads to Effects Similar to Placebo: A Controlled Study in Parkinson's Disease

Background. Random whole body vibration (WBV) training leads to beneficial short-term effects in patients with Parkinson's disease (PD). However, the effect of WBV lasting several weeks is not clear. Objectives. The aim of this study was to assess a random WBV training over 5 weeks in PD. Methods. Twenty-one participants with PD were allocated to either an experimental or a placebo group matched by age, gender, and Hoehn&Yahr stage. The WBV training consisted of 5 series, 60 s each. In the placebo group, vibration was simulated. The primary outcome was the change of performance in Functional reach test (FRT), step-walk-turn task, biomechanical Gait Analysis, Timed up and go test (TUG), and one leg stance. Findings. In most of the parameters, there was no significant interaction of "time∗group." Both groups improved significantly in Gait parameters, TUG, and one leg stance. Only in the FRT [F(1,15) = 8.397; P < 0.05] and in the TUG [F(1,15) = 4.971; P < 0.05] the experimental group performed significantly better than the placebo group. Conclusions. Random WBV training over 5 weeks seems to be less effective than reported in previous studies performing short-term training. The slight improvements in the FRT and TUG are not clinically relevant.

The influence of intraoperative microelectrode recordings and clinical testing on the location of final stimulation sites in deep brain stimulation for Parkinson's disease

BACKGROUND

The goal of our study was to investigate the influence of intraoperative microelectrode recordings and clinical testing on the location of the final stimulation site in deep brain stimulation in Parkinson's disease.

METHODS

In 22 patients with Parkinson's disease we compared magnetic resonance imaging (MRI)-based and atlas-based targets with the adjusted stimulation sites after intraoperative, multitrack microelectrode recording (MER) and intraoperative and postoperative clinical testing. The investigation included 176 target/stimulation sites in 44 subthalamic nuclei (STNs), which were related to a standardised three-dimensional, MRI-defined STN.

RESULTS

Atlas-based targets were positioned more superior and more medial than the MRI-based targets, which were located in the centre of the MRI-STN. The optimal stimulation sites, found intraoperatively after MER and clinical testing, were located more lateral and slightly more superior than both planned targets. In the majority of the cases the location of the active contact was the most superior and most lateral of all target sites. The differences in the distributions of those four targets reached statistical significance. However, final active contacts were distributed throughout the MRI-defined STN and its immediate surroundings.

CONCLUSIONS

The adoption of microelectrode recordings and extensive clinical testing allows the adjustment of anatomical targeting even to unexpected stimulation sites in and around the MRI-defined STN.

Ultra-fast electron diffraction at surfaces: from nanoscale heat transport to driven phase transitions

Many fundamental processes of structural changes at surfaces occur on a pico- or femtosecond time scale. In order to study such ultra-fast processes, we have combined modern surface science techniques with fs-laser pulses in a pump-probe scheme. Reflection high energy electron diffraction (RHEED) with grazing incident electrons ensures surface sensitivity for the probing electron pulses. Utilizing the Debye-Waller effect, we studied the cooling of vibrational excitations in monolayer adsorbate systems or the nanoscale heat transport from an ultra-thin film through a hetero-interface on the lower ps-time scale. The relaxation dynamics of a driven phase transition far away from thermal equilibrium is demonstrated with the In-induced (8×2) reconstruction on Si(111). This surface exhibits a Peierls-like phase transition at 100K from a (8×2) ground state to (4×1) excited state. Upon excitation by a fs-laser pulse, this structural phase transition is driven into an excited (4×1) state at a sample temperature of 20K. Relaxation into the (8×2) ground state occurs after more than 150 ps.