Dystonia in Huntington's disease: Prevalence and clinical characteristics

Background: The prevalence and clinical characteristics of dystonia in Huntington's disease (HD) have not been formally assessed. Objectives: To study (1) the prevalence of dystonia in HD in a clinic population, (2) the clinical features of dystonia, and (3) clinical correlates of dystonia (for example, age, disease duration). Methods: Patients with HD attending the HD Center at the New York State Psychiatric Center were administered the Unified HD rating Scale and underwent a standardized 5.5-minute videotaped examination. Two neurologists reviewed the videotaped examination and rated the severity and constancy if dystonia, calculating a total dystonia score for each patient. Results: Prevalence of dystonia of any severity was 95.2%. Twenty-four of 42 (57.1%) had dystonia in at least one body region that was moderate and present more than half of the time, and seven of 42 (16.7%) had dystonia that was severe and constant. The most prevalent types of dystonia were internal shoulder rotation (64.3%), sustained fist clenching (47.1%), excessive knee flexion (42.9%), and foot inversion (42.9%). In 37 of 42 (88.1%) patients, there were more than two types of dystonia, and in the average patient, three to four types of dystonia. The mean severity was between 1 (mild) and 2 (moderate), and the mean constancy was between 2 present less than half of the time) and 3 (present more than half of the time). Multivariate linear regression revealed that disease duration (p = 0.005) and taking an antidopaminergic agent (p = 0.03) were positively associated with the total dystonia score. Conclusions: The majority of patients in this HD clinic exhibited some dystonia. The dystonia was present in several body regions and manifested by a variety of movements and postures not typical of idiopathic torsion dystonia. The dystonia was not bothersome to most patients, and its severity was a function of disease duration and use of an antidopaminergic agent.