Journal of Parkinson's Disease

Braak and others have proposed that Lewy body pathology LBP in Parkinson disease PD may arise not only in the brain but alternatively from an initial site in the gastrointestinal GI tract with subsequent passage to the central nervous system CNS through the vagus nerve or other routes. We tested this hypothesis by using both immunohistochemistry IHC and RT QuIC a form of alpha synuclein seed amplification assay SAA to detect alpha synuclein LBP in samples from selected brain regions and 10 GI tract sites taken from autopsies of 50 PD subjects and 128 elderly subjects without parkinsonism or dementia including 34 with IHC identified CNS incidental Lewy body disease ILBD and 94 with no Lewy body IHC pathology detected NLB. A positive SAA or IHC result was restricted to the GI tract in only 2 subjects while LBP by either SAA or IHC was restricted to the brain in 11 subjects. To fairly compare GI only with brain only synucleinopathy however we would have to do SAA on brain samples from all ILBD and NLB cases in at least 4 critical brain regions olfactory bulb medulla pons and amygdala. Further SAA of brain regions is estimated based on the proportional results to date to potentially identify 21 additional brain only LBP subjects total of 32 if it were done on all of the NLB subjects. From this brain only LBP is estimated to be 16 times more common than GI only LBP. To assess the clinical impact of SAA positive GI sites we found that the number of positive sites per subject is significantly correlated with UPDRS motor score and SCOPA AUT GI related scores including those for salivation straining constipation and bowel movement.

Background: Historically, OFF burden in Parkinsons disease has been primarily attributed to motor features. Recent studies highlight that non motor symptoms, and the predictability of OFF episodes also drive functional impairment, yet they are rarely measured in clinical practice. Objective: To identify which clinical features are most closely associated with OFF time and OFF impact, and to quantify the added explanatory value of temporal predictability, non-motor, and behavioural domains beyond a core motor model. Methods: We analysed 1,252 OFF only visits from 430 PPMI participants. Outcomes were MDS UPDRS IV 4.3 (OFF time) and 4.4 (OFF impact). Linear mixed effects models with a participant random intercept were fitted. The core motor model included OFF state motor severity, freezing, tremor, levodopa responsiveness, and dyskinesia, plus covariates. Predictability (IV; 4.5), non motor (mood, fatigue/sleep, autonomic/GI), and behavioural (impulse control behaviours) domains were then added to assess added influence beyond motor. Analyses were stratified by time since diagnosis (Pooled; [≤] 4y; [≥] 6y). Results: Clinical features explained more variance in OFF impact than OFF time (25.9% vs 8.1%). OFF time was primarily linked to OFF state motor severity/freezing, with levodopa responsiveness important early. For OFF impact, predictability produced the largest increment in marginal R squared beyond the core motor model (pooled and Late). Within the core motor model, tremor was the largest contributor to OFF impact. Conclusions: Predictability is a prominent correlate of OFF impact. Asking about predictability may help tailor therapy, from timing optimisation to on demand rescue for unpredictable episodes.

Background: Visual dysfunction is a common but underrecognized contributor to disability in Parkinsons disease (PD), particularly deficits in binocular vision and vergence that impair reading, near work, and quality of life. The relationship between objective oculomotor abnormalities and patient-reported visual disability remains incompletely understood. Methods: We studied 25 individuals with PD and 11 age-matched controls who completed the National Eye Institute Visual Function Questionnaire 25 (VFQ25) and the Convergence Insufficiency Symptom Survey (CISS). Participants underwent comprehensive clinical ophthalmologic assessment and high resolution binocular eye tracking to quantify vergence latency, gain, fixation dynamics, and drift variability. Associations between objective measures and patient reported outcomes were examined, and predictive models were developed using clinic-only and combined clinical plus eye tracking approaches. Results: Compared with controls, PD participants demonstrated significantly worse VFQ25 composite scores and higher CISS scores, driven primarily by impairments in near activities and mental health. Clinically, PD was characterized by convergence insufficiency rather than generalized visual loss. Objective eye tracking revealed delayed vergence initiation, reduced gain, and increased instability. In PD, both clinical convergence measures (notably nearpoint convergence) and dynamic eye tracking metrics strongly correlated with VFQ25 and CISS scores, whereas such relationships were absent in controls. Predictive models showed limited performance using clinic measures alone, but improved with inclusion of eye racking variables. Conclusions: Visual disability in PD is tightly linked to convergence insufficiency and dynamic oculomotor instability. Simple clinical measures such as nearpoint convergence, augmented by eye tracking when available, provide meaningful insight into patient reported visual quality of life.

BackgroundLRRK2-Parkinsons disease (LRRK2-PD) is biologically heterogeneous with approximately 30% lacking aggregated alpha synuclein (Syn) in cerebrospinal fluid by seed amplification assay (SAA). Prior work has suggested slower progression in LRRK2-PD compared to sporadic PD (sPD). ObjectiveWe aimed to assess how LRRK2-PD with Syn aggregates on SAA (S+ LRRK2-PD) compares to S+ sPD. MethodsData from the Parkinsons Progression Markers Initiative were used to compare S+ LRRK2-PD and S+ sPD cohorts propensity score-matched on age, disease duration, sex and levodopa equivalent dose (N = 79 per cohort). Baseline clinical and biological features and 4-year longitudinal features were assessed. ResultsAt baseline, S+ LRRK2-PD participants had lower motor scores and dopaminergic deficit. Among measures showing within group progression, longitudinal trajectories did not differ significantly between groups. ConclusionsLongitudinal clinical progression of S+ LRRK2-PD and sPD in the PPMI study is similar despite differences in baseline features.

Olfactory decline is a well-established aspect of Parkinsons disease (PD) and is considered one of its earliest signs, often preceding motor symptoms by years to decades. However, because olfactory impairment is also common in healthy aging and other medical conditions, current olfactory tests that score performance (odor detection, discrimination, and identification) lack disease specificity. In contrast to performance scores, olfactory perceptual fingerprints are derived from odor ratings and sniffing behavior, and provide a stable measure of how the world smells to an individual. To test the hypothesis that olfactory perceptual fingerprints may provide a disease-specific marker, we obtained them in three cohorts: Individuals with PD (n=33), healthy age-matched controls (n=33), and critically, in participants with non-PD olfactory dysfunction (n=28). Consistent with previous results, a standard clinical olfactory test detected impairment in both PD and non-PD olfactory dysfunction, but failed to distinguish between these two groups. In contrast, olfactory perceptual fingerprints detected impairment, and distinguished PD from non-PD olfactory dysfunction at 88% accuracy (SVM classification, leave-one-out cross validation, 90% sensitivity, 85% specificity, P=3.2x10-4), or 94% accuracy after matching age and sex (SVM classification, leave-one-out cross-validation, 100% sensitivity, 88% specificity, P=0.0047). The difference between PD related and unrelated olfactory decline was particularly evident in sniffing behavior: Whereas both healthy participants and non-PD olfactory decline groups decreased sniff duration in response to unpleasant odors (-12.5% and -11.36% respectively), individuals with PD paradoxically increased sniff duration (+1.69%; P=4.5x10-5). Thus, PD was marked not by loss of olfactory performance, but by a distinct shift in olfactory perception. These findings imply that olfactory perceptual fingerprints provide for a disease-specific marker in PD.

BackgroundParkinsons disease (PD) is a progressive neurodegenerative disorder with complex pathophysiology. The potential of integrating biomarkers of neuronal injury, neuroinflammation, and modulators of Wnt signaling for PD diagnosis remains largely unexplored. ObjectiveThis study aimed to evaluate the diagnostic and clinical predictive value of a ten-biomarker serum panel encompassing markers of neuronal injury (NSE, UCHL1), neuroinflammation (GFAP, HMGB1), synaptic plasticity (BDNF), proteinopathy (-Synuclein, {beta}-Amyloid-42), and Wnt signaling (R-spondin-1, DKK1, Sclerostin), with a particular focus on chronic fatigue in PD. MethodsIn this case-control study, 90 PD patients and 45 healthy controls were enrolled. Serum biomarkers were quantified using ELISA. Clinical severity was assessed using the Movement Disorder Society-Unified Parkinsons Disease Rating Scale (MDS-UPDRS) and Fibro-Fatigue (FF) scales. Binary logistic regression and multiple linear regression analyses were used to evaluate the diagnostic and predictive value of biomarkers for PD diagnosis, psychiatric and motoric scores, and an FF score reflecting chronic fatigue syndrome (CFS) severity. ResultsA model incorporating NSE, DKK1, and {beta}-Amyloid-42 effectively discriminated PD patients from controls, yielding an area under the curve (AUC) of 0.932 and an overall accuracy of 83.0%. NSE and DKK1 emerged as the main predictors of overall disease severity, motor symptoms, and CFS severity. Regression analyses indicated that 41.3% of the variance in the FF score was explained by increased NSE, DKK1, {beta}-amyloid, and UCHL1, while 42.9% of the variance in psychiatric symptoms was explained by increased NSE, DKK1, and {beta}-amyloid. Increased GFAP levels were significantly associated with motor dysfunction. ConclusionThe combined presence of neuronal injury, Wnt signaling dysregulation, and amyloid pathology may represent a key pathophysiological component underlying PD, CFS-like fatigue, and psychiatric symptoms in PD. Targeting neuronal injury and Wnt signaling pathways may offer novel therapeutic strategies for managing fatigue and psychiatric manifestations in PD.

Background: Most trials of Parkinson's disease (PD) measure progression over a short to medium time-period using continuous rating scales that may be hard to interpret and less meaningful for patients. There is a lack of evidence connecting changes in these scales to changes in outcomes important to patients. Objectives: We present causal modelling to translate the causal, short-term disease-modifying treatment effects on functional rating scales to the 10-year risk of serious clinical progression milestones. Methods: We selected four important clinical milestones of disease progression from the Oxford Parkinson's Disease Centre "Discovery" cohort: dementia, any falls, frequent falls, and mortality. We proposed a causal framework for our research objectives so we could model the potential impact of a 30% reduction in disease progression slopes ("treatment effect") using the summation of parts I and II of the Movement Disorders Society Unified Parkinson's Disease Rating Scale (UPDRS12). This outcome was regressed on time to milestone using flexible parametric survival models. Marginal predictions of survival and survival difference at year 10 were then calculated for the Discovery cohort, and a counterfactual cohort applying the treatment effect to estimate the relative and absolute reductions for the four clinical milestones. Results: The model increase in risk for each unit change in the UPDRS12 were as follows: dementia hazard ratio (HR)=1.52 (95% Confidence Interval (CI) 1.36-1.70), any falls HR=1.37 (95% CI 1.29-1.46), frequent falls HR=1.68 (95% CI 1.49-1.89), mortality=1.29 (95% CI 1.17-1.42). These models led to marginal predictions of absolute reductions, when the progression was reduced by 30%, between 4.0% (mortality) and 7.5% (frequent falls) at 10 years follow up. Conclusions: We have demonstrated how a treatment effect in a trial specified in terms of a progression change of a rating scale can be contextualised into a long-term reduction in the probability of clinically relevant milestones. Whilst we have used PD as our exemplar, we believe this methodological approach is generalisable to other chronic progressive diseases where trials are often limited to a relatively short follow-up period and use some scalar measure of progression, but significant clinical milestones usually take longer to be observed. Keywords: Clinical trials; disease modifying therapies; causal estimation; prediction models

ImportanceDementia is common in Parkinsons disease (PD), causing greater disability than other symptoms, but varies in timing. Although visual deficits are linked with PD dementia, how these interact with genetic factors to predict PD dementia has not been characterised. ObjectiveTo investigate whether visual deficits and genetic factors predict PD dementia. DesignLarge prospective longitudinal case-control study, mean follow-up 32.7 (SD=12.3) months. SettingCases were recruited between 2017-2020 at 35 UK PD clinics. ParticipantsPeople with PD without dementia at baseline were included. Main outcomes and measuresVisual function was measured using a web-based platform. The main outcome measure was global cognition, measured as the Montreal Cognitive Assessment (MoCA). Blood samples were collected for genetics. Results450 patients with PD were included. Mean age of PD patients was 71.7 (SD=7.8), 68% male. Mean baseline MoCA was 27.7 (SD=1.7). 263 patients with PD were classed as poor-vision based on baseline visual tests: mean age 74.4 (SD=6.8) compared to 69.7 (SD=7.5) with good-vision. Poor-vision PD patients had higher rates of progression to mild cognitive impairment (PD-MCI) (HR=2.34, CI=1.58-3.48, pFDR=0.00062, age- and sex-corrected). The combination of genetic factors together with vision influenced outcomes. In good-vision PD patients, high-risk GBA1 gene variants were linked with greater progression to PD-MCI (HR=4.61, CI=1.73-12.28, pFDR=0.0068). Polygenic Risk Score (PRS) for both PD and Alzheimers disease (AD) also modified cognitive survival when combined with vision status. High PD-PRS was associated with greater progression to PD-MCI in good-vision patients (HR=2.66, CI=1.21-5.81, pFDR=0.0381); and high AD-PRS with greater progression to PD-MCI in poor-vision PD patients (HR=1.91, CI=1.10-3.32, pFDR=0.04999). Combining high PD- and AD-PRS, compared to low PD- and AD-PRS in good-vision PD showed even higher progression to PD-MCI (HR=6.14, CI=1.36-27.83, pFDR=0.046). Simulations showed that adding visual and genetic stratification reduced sample size from n=705 to n=160 for clinical trials. Conclusions and relevancePoor vision in PD predicts progression to PD-MCI and dementia. This combines with the effects of genetic factors including GBA risk variants and PD- and AD-PRS. These findings can enable enrichment of clinical trials for patients at higher risk of PD dementia, for more efficient trial design for interventions to slow progression. Key pointsO_ST_ABSQuestionC_ST_ABSDo clinical factors, measured by performance on visual tests, and genetic factors help predict which patients are more likely to develop cognitive involvement in Parkinsons disease? FindingsThis prospective longitudinal study of 450 Parkinsons patients, based in Parkinsons clinics, with mean follow-up 32.7 months, found that Parkinsons patients with poor vision are more likely to develop cognitive impairment; and that genetic factors in combination with poor vision further predict poor prognostic groups for Parkinsons dementia. MeaningThese data could enable selection of Parkinsons patients at highest risk of dementia for clinical trials aimed at slowing Parkinsons dementia.

BackgroundParkinsons disease (PD) is a neurodegenerative disorder for which there is currently no cure or reliable biomarker for early detection or for evaluating the effectiveness of potential treatments. PD pathology is driven by misfolding and subsequent accumulation of alpha-synuclein (Syn) protein into pathological aggregates within neurons and glial cells. Seed amplification assay (SAA) is a highly sensitive and specific diagnostic tool developed to detect pathological Syn species in the cerebrospinal fluid (CSF) of PD patients. However, Syn aggregates are present in multiple tissues and biosamples, including stools. In this study, we aimed to investigate the potential diagnostic value of SAA using stool samples from PD patients and healthy controls (HC). MethodsStool samples from PD patients (n=45) and healthy controls (n=35) were analysed for the presence of Syn species using slot blot assays with a panel of six Syn antibodies, and ELISA assays. Samples were subjected to SAA, and the end-point products (SAA EP) were characterised using transmission electron microscopy (TEM). Extracellular vesicles (EVs) were isolated from the subset of samples (n=5 per group) using size exclusion chromatography and characterized by TEM. The seeding activity of isolated EVs was evaluated using SAA, followed by TEM analysis of SAA EP. ResultsProtein extracts from both PD and HC stool samples revealed pathological Syn species in the slot blot assay using the phosphorylated Syn antibody, pS129 and conformation-specific antibodies, MJFR-14 and 5G4. ELISA showed significantly elevated total Syn levels in PD samples compared to HC, although no differences in aggregated Syn levels were detected. In stool protein extracts, SAA demonstrated 55.6% sensitivity and 60% specificity. When applied to stool-derived EVs from PD patients and controls, sensitivity increased to 100%, while specificity remained at 60%. Notably, SAA applied to stool-derived EVs pre-incubated with recombinant monomeric Syn achieved 100% sensitivity and 100% specificity. ConclusionThese findings suggest that SAA applied to EVs isolated from stool samples, particularly after pre-incubation with recombinant monomeric Syn, may serve as a valuable, non-invasive screening tool for the diagnosis of PD.

Studies reporting alpha-synuclein seed amplification assay (aSyn-SAA) results are often cross-sectional. Here we investigated the intra-individual consistency of aSyn-SAA results over time from participants in the Parkinson's Progression Marker Initiative (PPMI). A total of 1238 participants had >1 CSF aSyn-SAA result for analysis (Parkinson's disease [PD]=633, prodromal =563, healthy control [HC]=42) which were collected over a median (min, max) of 2.0 (0.4, 11.4) years. Emphasis was placed on evaluating consistency in less common results such as aSyn-SAA- PD participants, aSyn-SAA+ HC and conversion rates from aSyn-SAA negative to positive results prodromal participants. Of aSyn-SAA+ PD participants, 96% (474/493, 95%CI 94-98%) remained positive in subsequent samples, and 92% (116/126, 95%CI 86-96%) of aSyn-SAA- PD participants remained negative. 99% (303/307, 95%CI 97-99%) of aSyn-SAA+ prodromal participants remained positive, and 95% (234/247, 95%CI 91-97%) of aSyn-SAA- prodromal participants remained negative. 89% (16/18, 95%CI 67-97%) of aSyn-SAA+ HC participants remained positive, and 87% (20/23, 95%CI 68-95%) of aSyn-SAA- HC participants remained negative. These results confirm a high consistency of aSyn-SAA results over time, even in less expected results.

Adeno-associated viral (AAV)-mediated overexpression of human wildtype -synuclein (-syn) in the substantia nigra (SN) is a widely used approach to model Parkinsons disease (PD) in rodents. However, variability in the ability of AAV-based systems to induce nigrostriatal pathology and motor deficits has limited reproducibility across studies, especially in mice. Here, we systematically optimized key vector features - AAV serotype, promoter, viral titer - to establish a highly efficient and reliable mouse model of PD. We compared the tropism and expression efficiency of mixed AAV2/1 and AAV2/rh10 serotypes combined with three promoters - CMV enhancer/chicken {beta}-actin (CBA), human Synapsin (hSYN), and rat Tyrosine Hydroxylase (TH) - to drive human -syn gene (SNCA) expression in nigral dopaminergic neurons. The AAV.TH.SNCA vector, delivered at an optimized titer, achieved selective and sustained -syn overexpression in nigral neurons, resulting in nigro-striatal neurochemical changes and progressive motor deficits preceding overt neuronal loss. Fine tuning -syn expression proved critical for detecting early disease processes: lower AAV.TH.SNCA titer induced early pathological signatures, including -syn hyperphosphorylation and neuroinflammation, whereas higher titers produced robust nigrostriatal degeneration not achieved with other promoter constructs. Notably, we demonstrate that motor and neurochemical impairments can occur prior to dopaminergic cell death, implicating microglial activation and -syn pathology as primary drivers of dysfunction. This observation is consistent with human genetic evidence showing that triplication of the wild-type SNCA gene alone can cause Parkinsonian pathology, highlighting that our model enables the use of a single experimental reagent to investigate the molecular, cellular, and behavioral consequences of controlled increases in -syn expression. This novel AAV.TH.SNCA model provides a powerful and versatile platform for investigating mechanisms of a -syn-mediated neurotoxicity and for evaluating disease modifying interventions targeting early, pre-degenerative stages of PD. HighlightsO_LITitrated -syn expression uncouples early dysfunction from dopaminergic neuron loss C_LIO_LIAAV2/rh10-TH-SNCA model captures prodromal and degenerative PD stages C_LIO_LIMotor deficits arise from -syn pathology and nigral molecular changes before neurodegeneration. C_LI

BackgroundParkinsons disease (PD) is a multifactorial neurodegenerative disorder shaped by, amongst others, high-impact variants and common polygenic factors. The Personalized Parkinson Project (PPP) offers deep phenotyping and longitudinal follow-up of Dutch people with PD. Here, we characterize the genetic landscape and its interaction with lifestyle factors within PPP. MethodsWe utilized three complementary approaches in N=507 persons with PD: 1) short-read PD gene panel sequencing of eight PD genes, 2) genome-wide genotyping array, and 3) targeted long-read sequencing of the GBA1 gene. Additionally, we calculated the mitochondrial-function polygenic score (MGS). Associations between genetic factors, smoking status, and age at onset (AAO) were assessed using non-parametric tests, correlation analyses, and multiple regression models. ResultsGenetic screening of the participants revealed N=79 GBA1 ([~]15%), N=3 LRRK2, N=1 CHCHD2, N=1 SNCA variant carrier, and N=9 heterozygous PRKN/PINK1 variants. We also observed an interaction between MGS and smoking: MGS was associated with earlier AAO in non-smokers in persons with iPD (N=414, {beta}=-1.87, p=0.038). ConclusionOur findings corroborate previously reported frequencies of variants in PD-associated genes in European populations, and suggest a potential association between smoking and a mitochondrial dysfunction signature in PD. Thus, even in persons without rare variants (iPD subgroup), complex genetic contributions remained relevant. Our study supports future downstream stratification and personalized medicine approaches with high-impact variants and polygenic risk scores.

Body-first Lewy body disease (LBD) is hypothesized to begin in the peripheral autonomic nervous system, years before nigrostriatal involvement. Isolated REM sleep behaviour disorder (iRBD) is considered prodromal body-first LBD, but the duration of the prodromal phase remains unknown. We aimed to determine the progression rate of cardiac sympathetic denervation using [123I]meta-iodobenzylguanidine (MIBG) scintigraphy and employ the resulting curves to estimate the prodromal period of body-first LBD. We analysed longitudinal MIBG and dopaminergic imaging data from three cohorts: early Parkinsons disease (PD) patients from KPD, Korea (KPD-PD; n=195); de novo PD (n=74) and iRBD (n=54) patients from the PACE cohort, Aarhus, Denmark; and DaT SPECT data from PPMI PD (n=426) and iRBD (n=37). Heart-to-mediastinum ratios (MIBG) and putamen-to-occipital ratios (DaT SPECT) were converted to percent of normal value (healthy control mean). Patients were binned into quartiles according to baseline imaging data and progression curves were constructed by using median decline rates within each quartile. Onset of cardiac sympathetic (peripheral) and nigrostriatal dopaminergic (central) neurodegeneration were determined for iRBD patients by back-extrapolation from baseline imaging values. Longitudinal MIBG trajectories were highly consistent across the KPD and PACE cohorts, showing a rapid early decline ([~]10%-points/year) followed by gradual slowing, reaching 50% of normal value after [~]5 years and 25% after [~]10 years. PACE-iRBD patients displayed severe baseline cardiac sympathetic loss (median 21.3% of normal), corresponding to an estimated onset of peripheral neurodegeneration 11.3 years prior to study enrolment. Dopaminergic decline was slightly slower, reaching 50% of normal value after [~]8 years and 25% after [~]15 years. PACE-iRBD patients exhibited mild baseline dopaminergic deficit (median 81.6% of normal), indicating onset of nigrostriatal degeneration 2.7 years prior to enrolment. Thus, cardiac sympathetic degeneration preceded nigrostriatal involvement by 8.6 years. Based on baseline dopaminergic degeneration in PACE-PD patients, predicted time to phenoconversion for PACE-iRBD patients was 8.4 years. The combined model estimated the total prodromal period in body-first LBD to exceed 19 years. In conclusion, our study suggests that cardiac sympathetic degeneration begins more than a decade before study enrolment in iRBD subjects and nearly two decades before LBD diagnosis. Therefore, MIBG scintigraphy is a robust biomarker for detecting the earliest measurable neurodegeneration of body-first LBD and may be integrated in biological staging of -synucleinopathies. Furthermore, our findings have implications for drug trial design in SAA-positive individuals, and for identifying patients at the optimal window for disease-modifying therapies.

Background: Dystonia frequently co-exists with Parkinson's disease (PD), yet the extent of genetic overlap remains insufficiently explored. Objective: To examine whether rare variants in dystonia-related genes are associated with PD or early-onset PD (EOPD). Methods: We curated 44 dystonia-related genes using OMIM and the updated Movement Disorder Society report on hereditary dystonia. Whole-genome sequencing data from 5,315 PD patients, including 300 with EOPD, and 36,902 controls across the Accelerating Medicines Partnership-PD and UK Biobank cohorts were analyzed. For each gene, we evaluated rare variants (minor allele frequency <1%) in four pre-specified variant classes: exonic, nonsynonymous, CADD score [&ge;]20 and loss-of-function. For the rare variant burden analysis, SKAT-O was performed, followed by meta-analysis with MetaSKAT. Results: In analyses of all PD cases, several genes showed nominal associations in meta-analysis: SQSTM1 (Ploss-of-function = 5.52 x 10-3), AOPEP (Pexonic = 6.96 x 10-3; Pnonsynonymous = 0.017), KCNA4 (Pexonic = 0.017), SPR (Pexonic = 0.029), SLC30A10 (PCADD[&ge;]20 = 0.046), and ACTB (Pexonic = 0.047). However, none remained significant after multiple-testing correction. In exploratory EOPD analyses, five genes reached significance after multiple test correction (ATP5MC3, DNAJC12, KMT2B, TBC1D24, TMEM151A). These signals were driven by small numbers of variants and were not robust to leave-one-variant-out analyses. GCH1 was nominally significant in the meta-analysis of EOPD (Pnonsynonymous = 4.36 x 10-3, PFDR = 0.062). Conclusions: Rare variants in dystonia-related genes do not appear to make a major contribution to PD risk overall. Signals observed in the EOPD subset were based on small numbers of variant carriers and require replication in larger cohorts.

ObjectiveTo evaluate whether the presence of orthostatic hypotension (OH) impacts the association between white matter hyperintensity (WMH) volume and motor symptom burden in persons with Parkinsons disease (PWP). MethodsMotor symptom burden in PWP was quantified using the Movement Disorders Society Unified Parkinsons Disease Rating Scale (MDS-UPDRS) Part III. Total WMH volume was segmented based on high-resolution T1-weighted (T1W) and T2 Fluid Attenuated Inversion Recovery (FLAIR) images. Determination of whether individual participants qualified as having OH was based on orthostatic vital signs. All data were obtained from the Parkinsons Progression Markers initiative (PPMI) dataset. ResultsA total of 218 PWP (mean age, 64.84 {+/-} 9.51) and 50 control participants (mean age, 65.52 {+/-} 11.04) were included in the analyses. WMH volume did not differ significantly between the two groups. 15.1% of the participants in the PD group and only 4% of the control group qualified as having OH. Analysis of covariance determined that in PWP, the association between WMH volume and motor symptom burden was significantly different in participants with OH in comparison to those without OH (steeper in the former group). Follow-up analyses suggested that the effects were strongest for bradykinesia symptoms. Adjusting for disease and symptom duration did not alter results. ConclusionsThe presence of OH in PWP impacts the links between white matter lesion volume and motor symptom burden. These findings may provide a potential mechanism underlying the poorer disease prognosis among PWP with OH.

BackgroundContinuous subcutaneous foslevodopa/foscarbidopa infusion (LDp/CDp-CSI) is an effective treatment for patients with Parkinsons disease (PD), but infusion-site nodules are a major cause of treatment discontinuation. Systemic inflammation can influence local skin tolerance; however, predictive biomarkers remain unidentified. ObjectiveTo evaluate the predictive value of the neutrophil-to-lymphocyte ratio (NLR) for clinically significant infusion-site nodules (PD-CSN) during LDp/CDp-CSI and to establish a clinical management framework to mitigate their development. MethodsWe prospectively followed 38 patients with PD initiating LDp/CDp-CSI for [&ge;]3 months. Baseline immunological data were collected before infusion. A subset of 30 patients was followed for an average of 11 months to identify factors associated with skin nodules at longer follow-up. Nodules were classified by blinded raters. Between-group comparisons, ANCOVA, ROC curve, and Kaplan-Meier analyses were performed. ResultsAt 3 months, 42% of patients were PD-CSN and showed higher baseline neutrophil counts (P=0.030) and NLR (P=0.007), with NLR remaining independently associated with nodule status (F=7.06, P=0.012). ROC analysis demonstrated acceptable discrimination (AUC=0.73, P=0.016). At last follow-up, lower baseline lymphocyte counts (P=0.002) and higher NLR (P=0.001) were observed in PD-CSN. High baseline NLR predicted earlier nodule onset (P=0.001). Despite frequent nodules, multidisciplinary team surveillance, including remote and in-person follow-up, limited treatment discontinuation to 5.3%. ConclusionsBaseline systemic inflammation, reflected by NLR, predicts both the onset and persistence of infusion-site nodules during LDp/CDp-CSI. NLR may serve as a clinically accessible biomarker for early risk stratification. Multidisciplinary surveillance facilitates timely nodule management and enhances treatment adherence.

Synucleinopathies, including idiopathic Parkinsons Disease, are driven by misfolding and aggregation of the 140 residue -synuclein protein that plays a role in presynaptic vesicle regulation. We describe effects of a modifier, neuronal overexpression of the mouse calcium-activated potassium channel subunit Kcnn1, on a mouse model in which transgenic Thy1.2-driven A53T -synuclein directs fully penetrant lethal motor disease. Kcnn1 overexpression increased median survival of these mice from 8.5 months to 18 months, associated with an altered clinical presentation from a rapidly progressive dystonic-like behavior of the limbs to a later-onset (12-16 mo) and slowly progressive lower limb clasping when lifted by the tail. At the tissue level, accretion of disease-associated phospho-serine 129 -synuclein was prevented by overexpression of Thy1.2-driven Kcnn1, which was observed in many brain regions, including the ones where phospho-serine 129 -synuclein was copiously accreted in A53T mice at endstage. The action of blocking production of phospho-serine 129 -synuclein was also observed in adult presymptomatic A53T mice injected with an AAV9 scCMV-Kcnn1 virus into the right superior colliculus. At endstage [~]2 months later, the right superior colliculus exhibited overexpression of Kcnn1 and showed essentially no phospho-serine 129 -synuclein, whereas the uninjected left superior colliculus exhibited copious phospho-serine 129 -synuclein. The neuroprotective action of Kcnn1 overexpression remains to be fully resolved, but the channel protein subunit, targeted to the ER membrane, has been shown to induce an ER stress response. This response, which may activate autophagy, along with potential channel formation, may diminish the rate of formation or lifetime of neurotoxic forms of A53T -synuclein.

ObjectiveIn Parkinsons disease (PD), gait-related digital mobility outcomes (DMOs) show promise for monitoring mobility decline, but convergent validity remains limited. To improve convergent validity, demonstrating convergence with motor severity scales and PD-specific neural mechanisms underlying mobility has been proposed. However, severity scales capture both PD-specific and non-specific factors. Requiring mechanistic evidence may favor DMOs that converge with underlying mechanisms, while those converging only with severity scales may be overlooked despite capturing broader mobility dimensions. Here, we asked whether PD-specific neural mechanisms underlying mobility enhanced the convergence of DMOs with motor severity scales - so that integrating mechanistic evidence in validation could improve (and not impede) convergent validity. MethodPrincipal component analysis was applied to task-based functional neuroimaging data to identify a measure associated with PD motor network dysfunction. An optimization problem was then formulated in which deep learning examined the convergence of a signal-based DMO with motor severity in laboratory and real-world contexts, and Tracing Gradient Descent assessed the influence of the identified measure on DMO-severity convergence. ResultsGreater PD motor network dysfunction was associated with reduced Attractor Complexity Index (ACI) values ({rho}=-0.54). Strong DMO-severity convergence was found across contexts ({rho}=|0.81-0.82|). Reduced ACI (i.e., greater PD motor network dysfunction) markedly enhanced DMO-severity convergence across contexts (rrb=|0.63-0.29|). ConclusionPD-specific neural mechanisms underlying mobility enhanced the convergence of a DMO with severity scales. SignificanceIntegrating mechanistic validation into DMO validation could improve convergent (and construct) validity, a prerequisite for regulatory approval and adoption in clinical trials and practice.

Deciding whether and how to act depends on a trade-off between the effort required to execute a given action and the potential reward for completing it. Impairments in this effort-reward trade-off have been proposed to underlie reduced movement vigor, or bradykinesia, in Parkinsons disease (PD). However, several mechanisms could alter the effort-reward trade-off in PD, each with unique implications for understanding and treating bradykinesia. Therefore, we individually examined whether people with PD (both on and off dopamine medication) demonstrated reduced sensitivity to reward value, increased perception of effort, or a biased mapping between effort and reward, compared to age- and sex-matched neurotypical controls. We found that people with PD exhibited increased effort perception and, surprisingly, no reduced sensitivity to reward value or a biased mapping between effort and reward. These findings suggest that effort perception could be an important factor driving bradykinesia in PD.

BackgroundOculomotor dysfunction is common in parkinsonian syndromes and ataxias, but its impact on patient-reported vision-related quality of life (VQoL) remains insufficiently understood. ObjectivesTo characterize VQoL across parkinsonian syndromes and ataxias and assess the functional significance of specific oculomotor abnormalities in spinocerebellar ataxias. MethodsParticipants were recruited at Massachusetts General Hospital (n=231): 104 with Parkinsons disease (PD), 10 with progressive supranuclear palsy (PSP), 56 with genetically defined ataxias (SCA2, SCA3, SCA6, SCA27B, CANVAS), and 61 healthy controls. VQoL was assessed using a 13-item subset of the Visual Activities Questionnaire targeting depth perception, visual acuity/spatial vision, and visual processing speed. Clinical severity was assessed with the Brief Ataxia Rating Scale and Modified International Cooperative Ataxia Rating Scale, and subjective symptoms with PROM-Ataxia. Group comparisons, correlations, and regression analyses were performed. ResultsAll disease groups reported significantly worse VQoL than controls, with the largest deficits in visual processing speed. PSP showed the greatest impairment across all domains, while PD was less affected. Individuals with SCA3 and SCA6 had significantly lower VQoL across all subcategories. In ataxias, VQoL correlated moderately with PROM-Ataxia and weakly with clinical oculomotor scores. Gaze-evoked nystagmus was the only oculomotor sign independently associated with reduced VQoL. ConclusionsParkinsonian syndromes and ataxias are associated with substantial VQoL impairment, particularly in visual processing speed. Gaze-evoked nystagmus is a key predictor of reduced VQoL in ataxias, highlighting the functional relevance of fixation instability. Patient-reported outcomes and oculomotor assessments are essential for capturing visual disability in clinical care and trials.