BACKGROUND AND PURPOSE: Huntington's disease (HD) is an autosomal dominant, 
neurodegenerative movement disorder, typically characterized by chorea. Dystonia 
is also recognized as part of the HD motor phenotype, although little work 
detailing its prevalence, distribution, severity and impact on functional 
capacity has been published to date.
METHODS: Patients (>18 years of age) were recruited from the Cardiff (UK) HD 
clinic, each undergoing a standardized videotaped clinical examination and 
series of functional assessment questionnaires (Unified Huntington's Disease 
Rating Scale, Burke-Fahn-Marsden Dystonia Rating Scale and modified version of 
the Toronto Western Spasmodic Torticollis Rating Scale). The presence and 
severity of dystonia were scored by four independent neurologists using the 
Burke-Fahn-Marsden Dystonia Rating Scale and Unified Huntington's Disease Rating 
Scale. Statistical analysis included Fisher's exact test, Wilcoxon test, anova 
and calculation of correlation coefficients where appropriate.
RESULTS: Forty-eight patients [91% (48/53)] demonstrated evidence of dystonia, 
with the highest prevalence in the left upper limb (n = 44, 83%), right upper 
limb most severely affected and eyes least affected. Statistically significant 
positive correlations (P < 0.05) were observed between dystonia severity and 
increasing HD disease stage and motor disease duration. Deterioration in 
functional capacity also correlated with increasing dystonia severity. No 
significant relationship was observed with age at motor symptom onset or CAG 
repeat length.
CONCLUSIONS: We report a high prevalence of dystonia in adult patients with HD, 
with worsening dystonia severity with increasing HD disease stage and motor 
disease duration. The recognition and management of dystonic symptoms in routine 
clinical practice will aid overall symptomatic treatment and functional 
improvement.