Publications

BACKGROUND: Task-specific dystonia (TSD) is a challenging clinical diagnosis with no objective diagnostic biomarkers.

OBJECTIVE: The objective of this study was to test 2 neurophysiologic variables using transcranial magnetic stimulation as potential diagnostic biomarkers for TSD.

METHODS: We tested (1) cortical silent period (CSP) and (2) dorsal inferior parietal lobule-motor cortex (dIPL-M1) physiologic connectivity in 9 patients with the writer's cramp form of TSD and 12 healthy volunteers on 2 separate sessions.

RESULTS: CSP was significantly prolonged (P < 0.0001) in TSD and could classify TSD with high sensitivity and specificity with areas under the receiver operating characteristic curve (AUCs) = 0.94 and 0.90, respectively, for 2 separate sessions with an intraclass correlation = 0.79. dIPL-M1 interaction was notable for significant motor cortical inhibition in TSD compared with facilitation in healthy subjects (P < 0.0001) and could classify TSD with high sensitivity and specificity with AUCs = 0.96 and 0.86, respectively.

CONCLUSION: CSP and dIPL-M1 physiologic connectivity can classify TSD with high sensitivity, specificity, reproducibility, and reliability.

INTRODUCTION: Despite evidence of the benefits of exercise, people with Parkinson's disease (PD) often exercise less than recommended. We sought to identify exercise class-related factors associated with the amount of exercise in PD communities.

METHODS: We used Parkinson's Outcome Project (POP) data from 3146 people with PD at 19 participating Centers of Excellence (COEs). POP data included self-reported moderate-vigorous exercise (MVE) hours, light physical activity (PA) hours, demographic and disease severity variables. We also collected information about weekly exercise class availability, intensity, cost, and distance from class location to the COE. We examined differences between COE-based and community-based exercise classes using the Akritas test for paired and unpaired samples. We tested associations between class characteristics and exercise hours based on a two-part model: logistic regression on whether a participant does MVE or light PA and linear regression for log-transformed time of exercise.

RESULTS: Community-based exercise classes had a significantly higher weekly availability than COE-based classes (class hours per week: 47.5 ± 25.6 vs 6.5 ± 8.6, p < 0.001), a higher percentage of vigorous-intensity classes (24.2 ± 17.8 vs 11 ± 14.7, p < 0.001), and a broader geographic distribution (miles to COE: 12.8 ± 4.6 vs 6.2 ± 5.7, p < 0.001). Greater weekly hours of availability, intensity, and distance to COE were associated with increased MVE and light PA hours among participants who exercised (p < 0.01). Of these, higher weekly class availability explained the most variability in reported exercise hours.

CONCLUSION: Parkinson's COEs may be able to increase exercise by facilitating a high weekly availability of exercise classes with higher intensity levels and broader geographical distribution.

BACKGROUND AND PURPOSE: Several clinical and demographic factors relate to anatomic spread of adult-onset isolated dystonia, but a predictive model is still lacking. The aims of this study were: (i) to develop and validate a predictive model of anatomic spread of adult-onset isolated dystonia; and (ii) to evaluate whether presence of tremor associated with dystonia influences model predictions of spread.

METHODS: Adult-onset isolated dystonia participants with focal onset from the Dystonia Coalition Natural History Project database were included. We developed two prediction models, one with dystonia as sole disease manifestation ("dystonia-only") and one accepting dystonia OR tremor in any body part as disease manifestations ("dystonia OR tremor"). Demographic and clinical predictors were selected based on previous evidence, clinical plausibility of association with spread, or both. We used logistic regressions and evaluated model discrimination and calibration. Internal validation was carried out based on bootstrapping.

RESULTS: Both predictive models showed an area under the curve of 0.65 (95% confidence intervals 0.62-0.70 and 0.62-0.69, respectively) and good calibration after internal validation. In both models, onset of dystonia in body regions other than the neck, older age, depression and history of neck trauma were predictors of spread.

CONCLUSIONS: This predictive modeling of spread in adult-onset isolated dystonia based on accessible predictors (demographic and clinical) can be easily implemented to inform individuals' risk of spread. Because tremor did not influence prediction of spread, our results support the argument that tremor is a part of the dystonia syndrome, and not an independent or coincidental disorder.

OBJECTIVE: Previous work in Huntington's disease (HD) has shown that a sense of meaning and purpose (M&P) is positively associated with positive affect and well-being (PAW); however, it was unknown whether HD-validated patient-reported outcomes (PROs) influence this association and how M&P impacts PROs in the future. Our study was designed to examine if HD-validated PROs moderate the relationship between M&P and PAW and to evaluate if baseline M&P predicts 12- and 24-month changes in HD-validated PROs.

METHODS: This was a longitudinal, multicenter study to develop several PROs (e.g., specific for the physical, emotional, cognitive, and social domains) for people with HD (HDQLIFE). The sample consisted of 322 people with HD (n = 50 prodromal, n = 171 early-stage manifest, and n = 101 late-stage manifest HD). A single, multivariate linear mixed-effects model was performed with PAW as the outcome predicted by main effects for M&P and several moderators (i.e., an HD-validated PRO) and interactions between M&P and a given PRO. Linear-mixed models were also used to assess if baseline M&P predicted HD-validated PROs at 12 and 24 months.

RESULTS: Higher M&P was positively associated with higher PAW regardless of the magnitude of symptom burden, as represented by HD-validated PROs, and independent of disease stage. In our primary analysis, baseline M&P predicted increased PAW and decreased depression, anxiety, anger, emotional/behavioral disruptions, and cognitive decline at 12 and 24 months across all disease stages.

INTERPRETATION: These findings parallel those seen in the oncology population and have implications for adapting and developing psychotherapeutic and palliative HD interventions.

BACKGROUND: Several monogenic causes for isolated dystonia have been identified, but they collectively account for only a small proportion of cases. Two genome-wide association studies have reported a few potential dystonia risk loci; but conclusions have been limited by small sample sizes, partial coverage of genetic variants, or poor reproducibility.

OBJECTIVE: To identify robust genetic variants and loci in a large multicenter cervical dystonia cohort using a genome-wide approach.

METHODS: We performed a genome-wide association study using cervical dystonia samples from the Dystonia Coalition. Logistic and linear regressions, including age, sex, and population structure as covariates, were employed to assess variant- and gene-based genetic associations with disease status and age at onset. We also performed a replication study for an identified genome-wide significant signal.

RESULTS: After quality control, 919 cervical dystonia patients compared with 1491 controls of European ancestry were included in the analyses. We identified one genome-wide significant variant (rs2219975, chromosome 3, upstream of COL8A1, P-value 3.04 × 10-8 ). The association was not replicated in a newly genotyped sample of 473 cervical dystonia cases and 481 controls. Gene-based analysis identified DENND1A to be significantly associated with cervical dystonia (P-value 1.23 × 10-6 ). One low-frequency variant was associated with lower age-at-onset (16.4 ± 2.9 years, P-value = 3.07 × 10-8 , minor allele frequency = 0.01), located within the GABBR2 gene on chromosome 9 (rs147331823).

CONCLUSION: The genetic underpinnings of cervical dystonia are complex and likely consist of multiple distinct variants of small effect sizes. Larger sample sizes may be needed to provide sufficient statistical power to address the presumably multi-genic etiology of cervical dystonia. © 2021 International Parkinson and Movement Disorder Society.

OBJECTIVE: Previous work in Huntington's disease (HD) has shown that a sense of meaning and purpose (M&P) is positively associated with positive affect and well-being (PAW); however, it was unknown whether HD-validated patient-reported outcomes (PROs) influence this association and how M&P impacts PROs in the future. Our study was designed to examine if HD-validated PROs moderate the relationship between M&P and PAW and to evaluate if baseline M&P predicts 12- and 24-month changes in HD-validated PROs.

METHODS: This was a longitudinal, multicenter study to develop several PROs (e.g., specific for the physical, emotional, cognitive, and social domains) for people with HD (HDQLIFE). The sample consisted of 322 people with HD (n = 50 prodromal, n = 171 early-stage manifest, and n = 101 late-stage manifest HD). A single, multivariate linear mixed-effects model was performed with PAW as the outcome predicted by main effects for M&P and several moderators (i.e., an HD-validated PRO) and interactions between M&P and a given PRO. Linear-mixed models were also used to assess if baseline M&P predicted HD-validated PROs at 12 and 24 months.

RESULTS: Higher M&P was positively associated with higher PAW regardless of the magnitude of symptom burden, as represented by HD-validated PROs, and independent of disease stage. In our primary analysis, baseline M&P predicted increased PAW and decreased depression, anxiety, anger, emotional/behavioral disruptions, and cognitive decline at 12 and 24 months across all disease stages.

INTERPRETATION: These findings parallel those seen in the oncology population and have implications for adapting and developing psychotherapeutic and palliative HD interventions.

OBJECTIVE: To determine the impact of percutaneous endoscopic gastrostomy (PEG) tubes in patients with advanced Huntington disease (HD).

METHODS: A retrospective chart review of patients with HD was conducted to assess the rate of pneumonia and pressure ulcer, length of life, changes in weight, and serologic nutritional measures. Surviving and deceased patients with and without PEG tubes were compared using descriptive statistical analysis.

RESULTS: One hundred forty-eight records were reviewed (39 patients with PEG tubes). The mean age of patients still alive and diagnosed with HD was 58.3 ± 12.7 years and age at death (n = 62) 57.7 ± 10.3 years. At the time of analysis, the mean duration of HD was 14.2 ± 7 years. Groups were similar in sex, age, and weight at admission. In those deceased, insertion of a PEG tube increased the length of life with HD by 3.6 years (16.2 ± 6.7 vs 13.2 ± 4.9 years). PEG tube placement significantly reduced cholesterol levels, increased the prevalence of skin ulcers and the rate of pneumonia. Insertion of a PEG tube did not significantly change weight or albumin levels.

CONCLUSIONS: PEG tube placement in advanced HD provided benefit in the length of life, but weight, other nutritional measures, and the rate of pneumonia were either not impacted or worsened with the insertion of a PEG tube. Impact on quality of life needs further study, but providers, patients, and families should consider all options when discussing preferences for interventions.

CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for patients with advanced HD, PEG tube placement increases the length of life but has no or negative impacts on nutritional measures.

OBJECTIVE: To assess the clinical manifestations and predictors of different types of tremors in individuals with different types of isolated dystonia.

METHODS: Clinical manifestations of tremor were assessed in a multicenter, international cross-sectional, cohort study of 2,362 individuals with all types of isolated dystonia (focal, segmental, multifocal, and generalized) recruited through the Dystonia Coalition.

RESULTS: Methodical and standardized assessments of all participants in this cohort revealed the overall prevalence of any type of tremor was 53.3%. The prevalence of dystonic tremor varied from 36.9% to 48.4%, depending on criteria used to define it. To identify the factors associated with tremors in dystonia, the data were analyzed by generalized linear modeling and cluster analyses. Generalized linear modeling indicated 2 of the strongest factors associated with tremor included body region affected by dystonia and recruitment center. Tremor was also associated with severity of dystonia and duration of dystonia, but not with sex or race. The cluster analysis distinguished 8 subgroups within the whole cohort; defined largely by body region with dystonia, and secondarily by other clinical characteristics.

CONCLUSION: The large number of cases evaluated by an international team of movement disorder experts facilitated the dissection of several important factors that influence the apparent prevalence and phenomenology of tremor in dystonia. These results are valuable for understanding the many differences reported in prior studies, and for guiding future studies of the nosology of tremor and dystonia.

IMPORTANCE: Urate elevation, despite associations with crystallopathic, cardiovascular, and metabolic disorders, has been pursued as a potential disease-modifying strategy for Parkinson disease (PD) based on convergent biological, epidemiological, and clinical data.

OBJECTIVE: To determine whether sustained urate-elevating treatment with the urate precursor inosine slows early PD progression.

DESIGN, PARTICIPANTS, AND SETTING: Randomized, double-blind, placebo-controlled, phase 3 trial of oral inosine treatment in early PD. A total of 587 individuals consented, and 298 with PD not yet requiring dopaminergic medication, striatal dopamine transporter deficiency, and serum urate below the population median concentration (<5.8 mg/dL) were randomized between August 2016 and December 2017 at 58 US sites, and were followed up through June 2019.

INTERVENTIONS: Inosine, dosed by blinded titration to increase serum urate concentrations to 7.1-8.0 mg/dL (n = 149) or matching placebo (n = 149) for up to 2 years.

MAIN OUTCOMES AND MEASURES: The primary outcome was rate of change in the Movement Disorder Society Unified Parkinson Disease Rating Scale (MDS-UPDRS; parts I-III) total score (range, 0-236; higher scores indicate greater disability; minimum clinically important difference of 6.3 points) prior to dopaminergic drug therapy initiation. Secondary outcomes included serum urate to measure target engagement, adverse events to measure safety, and 29 efficacy measures of disability, quality of life, cognition, mood, autonomic function, and striatal dopamine transporter binding as a biomarker of neuronal integrity.

RESULTS: Based on a prespecified interim futility analysis, the study closed early, with 273 (92%) of the randomized participants (49% women; mean age, 63 years) completing the study. Clinical progression rates were not significantly different between participants randomized to inosine (MDS-UPDRS score, 11.1 [95% CI, 9.7-12.6] points per year) and placebo (MDS-UPDRS score, 9.9 [95% CI, 8.4-11.3] points per year; difference, 1.26 [95% CI, -0.59 to 3.11] points per year; P = .18). Sustained elevation of serum urate by 2.03 mg/dL (from a baseline level of 4.6 mg/dL; 44% increase) occurred in the inosine group vs a 0.01-mg/dL change in serum urate in the placebo group (difference, 2.02 mg/dL [95% CI, 1.85-2.19 mg/dL]; P<.001). There were no significant differences for secondary efficacy outcomes including dopamine transporter binding loss. Participants randomized to inosine, compared with placebo, experienced fewer serious adverse events (7.4 vs 13.1 per 100 patient-years) but more kidney stones (7.0 vs 1.4 stones per 100 patient-years).

CONCLUSIONS AND RELEVANCE: Among patients recently diagnosed as having PD, treatment with inosine, compared with placebo, did not result in a significant difference in the rate of clinical disease progression. The findings do not support the use of inosine as a treatment for early PD.

TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02642393.

The choroid plexus (ChP) is a major source of cerebrospinal fluid (CSF) production, with a direct and indirect role in protein clearance, and pathogenesis of Alzheimer's disease (AD). Here, we tested the link between the ChP volume and levels of CSF proteins in 2 data sets of (i) healthy controls, mild cognitive impairment (MCI), and AD patients from the Alzheimer's Disease Neuroimaging Initiative (ADNI) (N = 509), and (ii) healthy controls and Parkinson's disease (PD) patients from the Parkinson's Progression Markers Initiative (N = 302). All patients had baseline CSF proteins (amyloid-β, total and phosphorylated-tau and α-synuclein (only in Parkinson's Progression Markers Initiative)). ChP was automatically segmented on 3T structural T1-weighted MRIs. We found negative associations between ChP volume and CSF proteins, which were stronger in healthy controls, early-MCI patients, and PD patients compared with late-MCI and AD patients. Further grouping of patients of ADNI dataset into amyloid-positive and amyloid-negative based on their florbetapir (AV45) PET imaging showed that the association between ChP volume and CSF proteins (t/p-tau) was lower in amyloid-positive group. Our findings support the possible role of ChP in the clearance of CSF proteins, provide evidence for ChP dysfunction in AD, and suggest the need to account for the ChP volume in future studies of CSF-based biomarkers.