Background Chorea may contribute to balance problems and walking difficulties that lead to higher fall rates in individuals with Huntington's disease (HD). Few studies have examined the effects of anti-choreic drugs on functional abilities. We noted that patients report decreased falls on stable dose of tetrabenazine, and we observed declines in gait and functional mobility when the drug was abruptly stopped.

Aims The purpose of this study is to compare: (1) spatiotemporal gait measures in forward and backward walking, (2) performance on functional mobility measures, and (3) amount of daily walking activity before and after administration of tetrabenazine in individuals with HD. It is hypothesised that the use of tetrabenazine to decrease chorea will improve gait, transfers and stair climbing.

Methods Evaluation of eight individuals on stable doses of tetrabenazine while off medication for >18 h and again 2 h following medication resumption. Individuals walked on the GAITRite and completed functional testing of UHDRS motor scores, Tinetti Mobility Test, Timed Sit-to-Stand Test and Timed Stair climbing.

Results As shown in prior studies, UHDRS motor scores showed significant improvement on drug vs off drug (p<0.001). A significant improvement was seen on both the Tinetti Balance Subscale (p=0.004) and the Tinetti Total Score (p=0.011); we have previously shown that the Tinetti correlates with fall risk. When compared to the on drug condition, variability of stride length in fast walking was higher (p=0.024), and swing time was significantly shorter in backward walking (p=0.020) off drug.

Conclusions The improvement of patients on gait measures as well as the Tinetti Mobility Test when on drug indicates that functional mobility is positively impacted by the use of tetrabenazine. Additional data collection is ongoing, including daily activity and fall data on subjects before and after starting tetrabenazine.