Clinical Assessment of the Effect of Tetrabenazine on Functional Scales in Huntington Disease: A Pilot Open Label Study

BACKGROUND: Tetrabenazine is a monoamine depleter with a well-documented effect against chorea associated with Huntington disease (HD). There is a paucity of data about how reduction in chorea relates to better performance on motor, gait, cognitive, and psychiatric assessments. METHODS: We designed an open label tetrabenazine withdrawal study to test performance using validated scales. The following instruments were used to assess cognitive, behavioral, and motor function in 10 patients with documented HD: The Montreal Cognitive Assessment, Beck Depression Inventory II, Dynamic Gait Index (DGI), Jebsen Hand Test, Timed 25-foot walk, Berg Balance Test (BBT), QuickDASH, and the Unified Huntington Disease Rating Scale (UHDRS) Motor, Stroop Color Word, Behavioral Assessment, Functional Checklist, and Independence Scale. RESULTS: Subjects performed significantly better while on tetrabenazine as measured by the DGI (p = 0.041), BBT (p = 0.007), and the UHDRS Total Motor (p = 0.009), Maximum Chorea (p = 0.005), and Stroop Color-Word tests (p = 0.028). DISCUSSION: This pilot study demonstrates tetrabenazine's potential effects beyond improvement in chorea.