Effect of tetrabenazine on Stroop interference in Huntington’s disease: protocol

Tetrabenazine has been shown to improve gating of abnormal visual stimuli and improve postural stability in Huntington’s disease (HD) patients as measured by computerized dynamic posturography testing. This open label pilot study aims to elucidate whether partial dopaminergic depletion via low dose tetrabenazine has a similar effect on masking out of abnormal visual stimuli on the Stroop interference test in HD patients. The study endpoint is the Golden formula calculated from off and on tetrabenazine Stroop test raw scores. The study will be performed as a single arm medication de novo or withdrawal trial. Informed consent to participate will be obtained from all participants and the next of kin. The data collection instrument is the standard Stroop color naming, word reading, and interference test. Stroop test will be administered to patients in the morning to patients who are off tetrabenazine (de novo or three-day withdrawal). 12.5 mg of TBZ will be administered just after the first Stroop test and also 3 hours later. On Stroop test will to be administered 6 hours after the off Stroop test. The raw Stroop word reading, color naming, and interference scores will be recorded and used for further analysis using Golden’s formula.