Cerebellar Gray Matter Alterations in Huntington Disease: A Voxel-Based Morphometry Study.

Neuropathological and neuroimaging studies in Huntington disease (HD) have suggested a role for the cerebellum. Our goal was to perform a detailed evaluation of cerebellar morphology. We performed the Unified HD rating scale (UHDRS) and Montreal cognitive assessment (MOCA) in 26 HD patients and 26 healthy controls. We created a two-sample test to analyze cerebellar gray matter (GM) differences between groups and another to correlate GM alterations with UHDRS and MOCA, corrected for age, expanded cytosine-adenine-guanine repeats, and disease duration using the spatially unbiased atlas template (SUIT)-SPM-toolbox which preserves anatomical detailing. We found increased GM density in the anterior cerebellum compared to controls. Higher GM density in the postero-superior lobe correlated with mood symptoms. Worse motor function and better cognitive function correlated with GM changes in the posterior cerebellum (false discovery rate (FDR) correction p < 0.05 and k > 100 voxels). In this detailed study of the in vivo cerebellar morphology in HD, we observed GM changes in regions involved in sensorimotor integration, motor planning, and emotional processing, supporting cerebellar involvement in the neuropathological process of HD.

Identification of extreme motor phenotypes in Huntington's disease.

The manifestation of motor signs in Huntington's disease (HD) has a well-known inverse relationship with HTT CAG repeat length, but the prediction is far from perfect. The probability of finding disease modifiers is enhanced in individuals with extreme HD phenotypes. We aimed to identify extreme HD motor phenotypes conditional on CAG and age, such as patients with very early or very late onset of motor manifestation. Retrospective data were available from 1,218 healthy controls and 9,743 HD participants with CAG repeats ≥40, and a total of about 30,000 visits. Boundaries (2.5% and 97.5% quantiles) for extreme motor phenotypes (UHDRS total motor score (TMS) and motor age-at-onset) were estimated using quantile regression for longitudinal data. More than 15% of HD participants had an extreme TMS phenotype for at least one visit. In contrast, only about 4% of participants were consistent TMS extremes at two or more visits. Data from healthy controls revealed an upper cut-off of 13 for the TMS representing the extreme of motor ratings for a normal aging population. In HD, boundaries of motor age-at-onset based on diagnostic confidence or derived from the TMS data cut-off in controls were similar. In summary, a UHDRS TMS of more than 13 in an individual carrying the HD mutation indicates a high likelihood of motor manifestations of HD irrespective of CAG repeat length or age. The identification of motor phenotype extremes can be useful in the search for disease modifiers, for example, genetic or environmental such as medication. © 2016 Wiley Periodicals, Inc.

Interleukin-6 as a marker of Huntington's disease progression: Systematic review and meta-analysis.

Huntington's disease (HD) is a rare, inherited disorder with a broad spectrum of manifestations that vary with disease severity and progression. Although genetic testing can readily confirm the initial diagnosis of HD, markers sensitive to HD progression are needed to aid the development of individual treatment plans. The current analysis aims to identify plasma Interleukin-6 (IL-6) as a marker of disease progression in HD patients. A systematic search of PubMed and Medline from conception through October 2021 was conducted. Studies reporting plasma IL-6 levels of mutation-positive HD patients and healthy controls that met inclusion criteria were selected. The search strategy collected 303 studies, 9 of which met analysis inclusion criteria. From included studies, plasma IL-6 levels of 469 individuals with the HD mutation and 206 healthy controls were collected. Plasma IL-6 levels were meta-analytically compared between healthy controls and individuals with the confirmed HD mutation at all stages of disease and correlated to performance on standardized measures of total cognitive and motor function. Plasma IL-6 was significantly increased in HD groups compared to controls (g = 0.73, 95% CI = 0.31,1.16, P < 0.01) and increased significantly throughout most stages of disease progression, notably between pre-manifest and manifest (g = 0.31, 95% CI = 0.04,0.59, P < 0.05) and early and moderate HD stages (g = 0.52, 95% CI = 0.18,0.86, P < 0.01). Significant correlations between plasma IL-6 levels and HD symptomatic progression were identified, with increased cytokine levels associated with more severe motor impairments (r = 0.179, 95% CI = 0.0479,0.304, P = 0.008) and more extreme disabilities in activities of daily living and/or work tasks (r = -0.229, 95% CI = -0.334, -0.119, P < 0.001). Conclusively, plasma IL-6 levels correlate with disease and motor symptom progression and may act as a viable marker for clinical use. Analysis is limited by small study numbers and highlights the need for future work to identify definitive ranges or rates of change of plasma IL-6 levels that correlate to progressive HD disease states.

The Chinese Version of UHDRS in Huntington's Disease: Reliability and Validity Assessment.

BACKGROUND: The Unified Huntington's Disease Rating Scale (UHDRS) is a universal scale assessing disease severity of Huntington's disease (HD). However, the English version cannot be widely used in China, and the reliability and validity of the Chinese UHDRS have not yet been confirmed. OBJECTIVE: To test the reliability and validity of Chinse UHDRS in patients with HD. METHODS: Between August 2013 and August 2021, 159 HD patients, 40 premanifest HD, and 64 healthy controls were consecutively recruited from two medical centers in China and assessed by Chinese UHDRS. Internal consistency and interrater reliability of the scale were examined. Intercorrelation was performed to analyze the convergent and divergent validity of the scale. A receiver operating characteristic analysis was conducted to explore the optimal cutoff point of each cognitive test. RESULTS: High internal consistency was found in Chinese UHDRS, and its Cronbach's alpha values of the motor, cognitive, behavioral and functional subscales were 0.954, 0.826, 0.804, and 0.954, respectively. The interrater reliability of the total motor score was 0.960. The convergent and divergent validity revealed that motor, cognitive and functional subscales strongly related to each other except for Problem Behavior Assessment. Furthermore, we not only provided the normal level of each cognitive test in controls, but also gave the optimal cutoff points of cognitive tests between controls and HD patients. CONCLUSION: We demonstrate for the first time that the translated version of UHDRS is reliable for assessing HD patients in China. This can promote the universal use of UHDRS in clinical practice.

Differential tractography as a dynamic imaging biomarker: A methodological pilot study for Huntington's disease.

Huntington's disease (HD) is a neurodegenerative disorder characterized by motor, psychiatric, and cognitive symptoms. Due to its diverse manifestations, the scientific community has long recognized the need for sensitive, objective, individualized, and dynamic disease assessment tools. We examined the feasibility of Differential Tractography as a biomarker to evaluate correlation of symptom severity and of HD progression at the individual level. Differential tractography is a novel tractography modality that maps pathways with axonal injury characterized by a decrease of anisotropic diffusion pattern. We recruited sixteen patients scanned at 0-, 6-, and 12-month intervals by diffusion MRI scans for differential tractography assessment and correlated its volumetric findings with the Unified Huntington's Disease Rating Scale (UHDRS). Deterministic fiber tracking algorithm was applied. Longitudinal data was modeled using the generalized estimating equation (GEE) model and correlated with UHDRS scores, in addition to Spearman correlation for cross-sectional data. Our results show that volumes of affected pathways revealed by differential tractography significantly correlated with UHDRS scores in longitudinal data (p-value < 0.001), and chronological changes in differential tractography also correlated with the changes in UHDRS (p-value < 0.001). This technique opens new clinical avenues as a clinical translational tool to evaluate presymptomatic and symptomatic gene positive individuals. Our results provide support that differential tractography has the potential to be used as a dynamic imaging biomarker to assess at the individual level in a non-invasive manner, disease progression in HD. Critically important, differential tractography proves to be a quantitative tool for following degeneration in presymptomatic patients, with potential applications in clinical trials.

Sleep Quality and Related Clinical Manifestations in Huntington Disease.

(1) Background: Sleep patterns are frequently disrupted in neurodegenerative disorders such as Huntington disease (HD); however, they are still poorly understood, especially their association with clinic features. Our study aimed to explore potential correlations between sleep features and motor, cognitive, behavioural and functional changes in manifest HD subjects. (2) Methods: We enrolled 42 patients who were assessed by the Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index (ISI) questionnaires; clinical features were evaluated by the validated ENROLL-HD platform assay, including the Unified Huntington's Disease Rating Scale (UHDRS) and the Problem Behaviours Assessment Short Form (PBA-s). (3) Results: We found a significant association between the patients' perception of sleep abnormalities and scores of impaired independence, cognitive and motor performances. Specifically, sleep efficiency (PSQI-C4 subscores) and the use of sleep medications (PSQI-C6 subscores) seem to be more frequently associated with the severity of the disease progression. (4) Conclusion: sleep abnormalities represent an important part of the HD clinical profile and can impair patients' quality of life by affecting their level of independence, cognition performance and mental well-being.

Deep brain stimulation and stereotactic-assisted brain graft injection targeting fronto-striatal circuits for Huntington's disease: an update.

INTRODUCTION: Huntington's Disease as progressive neurological disorders associated with motor, behavioral, and cognitive impairment poses a therapeutic challenge in case of limited responsiveness to established therapeutics. Pallidal deep brain stimulation and neurorestorative strategies (brain grafts) scoping to modulate fronto-striatal circuits have gained increased recognition for the treatment of refractory Huntington's disease (HD). AREAS COVERED: A review (2000-2022) was performed in PubMed, Embase, and Cochrane Library covering clinical trials conceptualized to determine the efficacy and safety of invasive, stereotactic-guided deep-brain stimulation and intracranial brain-graft injection targeting the globus pallidus and adjunct structures (striatum). EXPERT OPINION: Stereotactic brain-grafting strategies were performed in few HD patients with inconsistent findings and mild-to-moderate clinical responsiveness with a recently published large, randomized-controlled trial (NCT00190450) yielding negative results. We identified 19 in-human DBS trials (uncontrolled) targeting the globus pallidus internus/externus along with randomized-controlled trial pending report (NCT02535884). We did not detect any significant changes in the UHDRS total score after restorative injections, while in contrast, the use of deep-brain stimulation resulted in a significant reduction of chorea. GPi-DBS should be considered in cases where selective chorea is present. However, both invasive therapies remain experimental and are not ready for the implementation in clinical use.

Influence of Age of Onset on Huntington's Disease Phenotype.

Background: Older patients with Huntington's disease (HD) are often thought to have a slower progressing disease course with less behavioral symptoms than younger patients. However, phenotypic differences based on age of onset have not been well characterized in a large HD population. This study will determine the difference in manifestations and disease progression between patients with young, typical, and late onset adult HD at different stages of disease. Methods: Data obtained from Enroll-HD. Adults with manifest HD were included. Age groups were defined as young onset (YO: 20-29 years), typical onset (TO: 30-59 years), and late onset (LO: 60+ years). Subjects were categorized by TFC score, from Stage I (least severe) to Stage V (most severe). Motor, cognitive, and behavioral symptoms were analyzed. Descriptive statistics and Bonferroni p-value correction for pairwise comparison were calculated. Results: 7,311 manifest HD participants were included (612 YO, 5,776 TO, and 923 LO). The average decline in TFC score from baseline to second visit (1.5-2.5 years) was significantly faster for YO (-1.75 points) compared to TO (-1.23 points, p = 0.0105) or LO (-0.97 points, p = 0.0017). Motor deficits were worse for LO participants at early stages of HD, and worse for YO participants at advanced stages. YO and TO participants had greater burden of behavioral symptoms at early stages of disease compared to LO. Discussion: YO is predictive of a faster functional decline for adults with HD when compared to those with TO and LO. Motor and behavioral manifestations differ based on age of onset. Highlights: This study compares HD manifestations while controlling for disease severity, detailing robust phenotypic differences by age of onset alone. These findings have implications for the clinical management of HD symptoms and have the possibility to improve prognostic and treatment precision.

The Neuropsychiatry of Huntington Disease-Like 2: A Comparison with Huntington's Disease.

BACKGROUND: Huntington Disease-Like 2 (HDL2) is a rare autosomal dominant disorder caused by an abnormal CAG/CTG triplet repeat expansion on chromosome 16q24. The symptoms of progressive decline in motor, cognitive and psychiatric functioning are similar to those of Huntington's disease (HD). The psychiatric features of the HDL2 have been poorly characterized. OBJECTIVE: To describe the neuropsychiatric features of HDL2 and compare them with those of HD. METHODS: A blinded cross-sectional design was used to compare the behavioural component of the Unified Huntington's Disease Rating Scale (UHDRS) in participants with HDL2 (n = 15) and HD (n = 13) with African ancestry. RESULTS: HDL2 patients presented with psychiatric symptoms involving mood disturbances and behavioural changes that were not significantly different from those in the HD group. Duration of disease and motor performance correlated (p < 0.001) with the Functional Capacity score and the Independence score of the UHDRS. HD patients reported movement dysfunction as the first symptom more frequently than HDL2 Patients (p < 0.001). CONCLUSION: The psychiatric phenotype of HDL2 is similar to that of HD and linked to motor decline and disease duration. Psychiatric symptoms seem more severe for HDL2 patients in the early stages of the disease.

Cognitive and Motor Norms for Huntington's Disease.

BACKGROUND: The progression of Huntington's disease (HD) for gene-expanded carriers is well-studied. Natural aging effects, however, are not often considered in the evaluation of HD progression. OBJECTIVE: To examine the effects of natural aging for healthy controls and to develop normative curves by age, sex, and education from the distribution of observed scores for the Symbol Digit Modalities Test, Stroop Word Reading Test, Stroop Color Naming Test, Stroop Interference Test, Total Motor Score, and Total Functional Capacity (TFC) from the Unified Huntington's Disease Rating Scale (UHDRS) along with a composite score. METHODS: After combining longitudinal REGISTRY and Enroll-HD data, we used quantile regression and natural cubic splines for age to fit models for healthy controls (N = 3,394; N observations = 8,619). Normative curves were estimated for the 0.05, 0.25, 0.50, 0.75, and 0.95 quantiles. Two types of reference curves were considered: unconditional curves were dependent on age alone, whereas conditional curves were dependent on age and other covariates, namely sex and education. RESULTS: Conditioning on education was necessary for the Symbol Digit, Stroop Word, Stroop Color, Stroop Interference, and composite UHDRS. Unconditional curves were sufficient for the Total Motor Score. TFC was unique in that the curve was constant over age with its intercept at the maximum score (TFC = 13). For all measures, sex effects were minimal, so conditioning on sex was unwarranted. CONCLUSIONS: Extreme quantile estimates for each measure can be considered as boundaries for natural aging and scores falling beyond these thresholds are likely the result of disease progression. Normative curves and tables are developed and can serve as references for clinical characterization in HD.

Extrastriatal degeneration correlates with deficits in the motor domain subscales of the UHDRS.

INTRODUCTION: Striatal degeneration has significant behavioral effects in patients with Huntington's disease (HD). However, there is scant evidence of the possible contribution of extrastriatal regions to the motor alterations assessed within the different domains of the Unified Huntington's Disease Rating Scale (UHDRS). OBJECTIVE: Analyze if extrastriatal grey matter decrease in patients with HD correlates with motor performance assessed with the UHDRS and its different domains. METHOD: Twenty-two molecular diagnosed patients with incipient HD, and twenty-two control participants matched for sex and age participated in this study. Voxel-based morphometry (VBM) analyses were done to identify grey matter decrease in the HD patients, and its relationship with the motor deterioration measured with the UHDRS motor scale. To further explore this relationship, a principal component analysis (PCA) was done on the UHDRS domains scores. Then the average of each component was used as a covariate in a VBM analysis. Finally, individual sub-scores from each domain were also tested for correlations with the VBM results. RESULTS: In addition to the striatal degeneration, the VBM analysis showed significant negative correlations between the global UHDRS scores and the cerebellum, insula and precuneus atrophy. The UHDRS PCA showed component-related negative correlations suggesting a specific impact of individual degnerations. Further analyses with the individual sub-scores showed more specific corelations, including: chorea, with right caudate and left posterior cingulate gyrus; ocular pursuit, with left precentral gyrus, left superior temporal gyrus, cerebellum culmen and right temporal lobe. Saccadic movements with left postcentral gyrus and left middle occipital gyrus. CONCLUSION: In the early stages of HD, it is possible to find correlations between behavioral alterations as measured with the UHDRS motor domains, and extrastriatal regions, including specific areas of the cerebellum, and insular, parietal and frontal cortices. These areas could contribute to the HD related impairments along with the classical deficits associated with the striatal degeneration.

Reduced amygdala volumes are related to motor and cognitive signs in Huntington's disease: The IMAGE-HD study.

In Huntington's disease (HD), the presence of neurodegeneration in brain regions other than the striatum has been recently gaining attention. The amygdala is one such area, which has been investigated in only eight structural magnetic resonance imaging studies to date, but with inconsistent findings. This is the largest MRI study to date examining manually traced amygdala volumes in HD participants and the relationship of amygdala volumes to clinical measures of HD. Our study included 35 healthy control participants, and groups of 35 pre-symptomatic, and 36 symptomatic HD participants. When comparing the pre-symptomatic and symptomatic HD groups together against the control group, amygdala volumes were significantly lower in HD than controls and in symptomatic HD than pre-symptomatic HD. When examining relationships between amygdala volumes and clinical measures of HD, significantly smaller amygdala volumes were associated with worse motor and cognitive signs. For pre-symptomatic HD participants who were close to disease onset, smaller amygdala volumes were also associated with higher levels of anxiety symptoms. These findings suggest that the amygdala is affected in pre-symptomatic and symptomatic HD, and that the amygdala is related to the clinical profile of HD before onset of motor symptoms.

Exercise effects in Huntington disease.

Huntington disease (HD) is a relentlessly progressive neurodegenerative disorder with symptoms across a wide range of neurological domains, including cognitive and motor dysfunction. There is still no causative treatment for HD but environmental factors such as passive lifestyle may modulate disease onset and progression. In humans, multidisciplinary rehabilitation has a positive impact on cognitive functions. However, a specific role for exercise as a component of an environmental enrichment effect has been difficult to demonstrate. We aimed at investigating whether endurance training (ET) stabilizes the progression of motor and cognitive dysfunction and ameliorates cardiovascular function in HD patients. Twelve male HD patients (mean ± SD, 54.8 ± 7.1 years) and twelve male controls (49.1 ± 6.8 years) completed 26 weeks of endurance training. Before and after the training intervention, clinical assessments, exercise physiological tests, and a body composition measurement were conducted and a muscle biopsy was taken from M. vastus lateralis. To examine the natural course of the disease, HD patients were additionally assessed 6 months prior to ET. During the ET period, there was a motor deficit stabilization as indicated by the Unified Huntington's Disease Rating Scale motor section score in HD patients (baseline: 18.6 ± 9.2, pre-training: 26.0 ± 13.7, post-training: 26.8 ± 16.4). Peak oxygen uptake ([Formula: see text]) significantly increased in HD patients (∆[Formula: see text] = +0.33 ± 0.28 l) and controls (∆[Formula: see text] = +0.29 ± 0.41 l). No adverse effects of the training intervention were reported. Our results confirm that HD patients are amenable to a specific exercise-induced therapeutic strategy indicated by an increased cardiovascular function and a stabilization of motor function.

The quality of life of Spanish patients with Huntington's disease measured with H-QoL-I and EQ-5D.

BACKGROUND AND OBJECTIVE: Huntington's disease (HD) is an inherited neurodegenerative disorder that heavily affects the patient's motor, cognitive, and psychological functions. Yet, very few studies have measured the impact of this disease on the patient's health-related quality of life (HRQoL) with specific and validated instruments. The aim of this study was to explore the impact of HD on the HRQoL of Spanish HD patients using the self-reported, Huntington Quality of Life Instrument (H-QoL-I) and the generic instrument EuroQoL five dimensions (EQ-5D-3L) and thereafter compare the results obtained with the two instruments. METHODS: Fifty-five patients and an equal number of caregivers participated. Patient assessments included the questionnaires of the Huntington Self-Assessment Instrument's four parts: background information assessment, Huntington clinical self-reported instrument, disease-specific HRQoL assessment (H-QoL-I instrument) and Huntington resource utilisation interview, and the EQ-5D-3L questionnaire. Levels of disease severity were also determined based on the Unified Huntington's Disease Rating Scale that was completed by caregivers. Pearson's correlation tests were computed between H-QoL-I and EQ-5D-3L scores. RESULTS: The scores obtained with the H-QoL-I instrument showed that motor dimension was the most altered followed by the psychological dimension while the social dimension was the least altered. Increase of disease severity resulted in lower patient QoL. The usual activities and anxiety/depression were the most severely altered dimensions according to the EQ-5D-3L results. Mobility was also altered to a great extent while pain was the least altered dimension. All correlations between H-QoL-I and EQ-5D-3L scores were moderate to high and statistically significant (p<0.01) with the exception of the correlation between H-QoL-I socialising score and EQ-5D-3L anxiety score. The highest correlations were found between H-QoL-I motor score and three EQ-5D-3L scores: mobility, self-care, and usual activity. CONCLUSIONS: The quality of life of the Spanish HD patients included in this study was severely affected by HD as demonstrated by the results of the generic EQ-5D-3L and the specific H-QoL-I instruments, which showed considerable impact of the disease on the motor and psychological functions. The H-QoL-I instrument was able to discern psychological and motor functioning dimensions that were altered by the disease with more specificity and accuracy than the generic instrument.

Early grey matter changes in structural covariance networks in Huntington's disease.

BACKGROUND: Progressive subcortical changes are known to occur in Huntington's disease (HD), a hereditary neurodegenerative disorder. Less is known about the occurrence and cohesion of whole brain grey matter changes in HD. OBJECTIVES: We aimed to detect network integrity changes in grey matter structural covariance networks and examined relationships with clinical assessments. METHODS: Structural magnetic resonance imaging data of premanifest HD (n = 30), HD patients (n = 30) and controls (n = 30) was used to identify ten structural covariance networks based on a novel technique using the co-variation of grey matter with independent component analysis in FSL. Group differences were studied controlling for age and gender. To explore whether our approach is effective in examining grey matter changes, regional voxel-based analysis was additionally performed. RESULTS: Premanifest HD and HD patients showed decreased network integrity in two networks compared to controls. One network included the caudate nucleus, precuneous and anterior cingulate cortex (in HD p < 0.001, in pre-HD p = 0.003). One other network contained the hippocampus, premotor, sensorimotor, and insular cortices (in HD p < 0.001, in pre-HD p = 0.023). Additionally, in HD patients only, decreased network integrity was observed in a network including the lingual gyrus, intracalcarine, cuneal, and lateral occipital cortices (p = 0.032). Changes in network integrity were significantly associated with scores of motor and neuropsychological assessments. In premanifest HD, voxel-based analyses showed pronounced volume loss in the basal ganglia, but less prominent in cortical regions. CONCLUSION: Our results suggest that structural covariance might be a sensitive approach to reveal early grey matter changes, especially for premanifest HD.

Comparison of cognitive and UHDRS measures in monitoring disease progression in Huntington's disease: a 12-month longitudinal study.

Progressive cognitive decline is a feature of Huntington's disease (HD), an inherited neurodegenerative movement disorder. Comprehensive neuropsychological testing is the 'gold standard' to establish cognitive status but is often impractical in time-constrained clinics. The study evaluated the utility of brief cognitive tests (MMSE and MoCA), UHDRS measures and a comprehensive neuropsychological tests battery in monitoring short-term disease progression in HD. Twenty-two manifest HD patients and 22 matched controls were assessed at baseline and 12-month. A linear mixed-effect model showed that although the HD group had minimal change in overall global cognition after 12 months, they did show a significant decline relative to the control group. The controls exhibited a practice effect in most of the cognitive domain scores over time. Cognitive decline at 12-month in HD was found in the executive function domain but the effect of this on global cognitive score was masked by the improvement in their language domain score. The varying practice effects by cognitive domain with repeated testing indicates the importance of comparing HD patients to control group in research trials and that cognitive progression over 12 months in HD should not be judged by changes in global cognitive score. The three brief cognitive tests effectively described cognition of HD patients on cross-sectional analysis. The UHDRS cognitive component, which focuses on testing executive function and had low variance over time, is a more reliable brief substitute for comprehensive neuropsychological testing than MMSE and MoCA in monitoring cognitive changes in HD patients after 12 months.

Deep brain stimulation for Huntington's disease: long-term results of a prospective open-label study.

UNLABELLED: OBJECT.: To date, experience of globus pallidus internus (GPi) deep brain stimulation (DBS) in the treatment of Huntington's disease (HD) has been limited to a small number of case reports. The aim of this study was to analyze long-term motor outcome of a cohort of HD patients treated with GPi DBS. METHODS: Seven patients with pharmacologically resistant chorea and functional impairment were included in a prospective open-label study from 2008 to 2011. The main outcome measure was the motor section of the Unified Huntington's Disease Rating Scale. The primary end point was reduction of chorea. RESULTS: Patients underwent MRI-guided bilateral GPi implantation. The median duration of follow-up was 3 years. A significant reduction of chorea was observed in all patients, with sustained therapeutic effect; the mean improvement on the chorea subscore was 58.34% at the 12-month follow-up visit (p = 0.018) and 59.8% at the 3-year visit (p = 0.040). Bradykinesia and dystonia showed a nonsignificant trend toward progressive worsening related to disease evolution and partly to DBS. The frequency of stimulation was 130 Hz for all patients. DBS-induced bradykinesia was managed by pulse-width reduction or bipolar settings. Levodopa mildly improved bradykinesia in 4 patients. Regular off-stimulation tests confirmed a persistent therapeutic effect of DBS on chorea. CONCLUSIONS: GPi DBS may provide sustained chorea improvement in selected HD patients with pharmacologically resistant chorea, with transient benefit in physical aspects of quality of life before progression of behavioral and cognitive disorders. DBS therapy did not improve dystonia or bradykinesia. Further studies including quality of life measures are needed to evaluate the impact of DBS in the long-term outcome of HD.