Impact of Xenazine(Tetrabenazine)on Gait and Functional Activity in Individuals With Huntington's Disease

Individuals with HD who are ambulatory and are either already taking Xenazine or have been newly prescribed the medication will be recruited for this prospective open-label study. A variety of motor assessments will be preformed while subject are taking Xenazine or after a period off of the medications. These tests include: Unified Huntington's Disease Rating Scale (UHDRS) motor section, GAITRite forward walking, Tinetti Mobility Test, Timed Sit-to-Stand Test, Timed Stair Climb Test, Rhomberg test. A subset of subjects will wear an activity monitoring device on the wrist of the non-dominant hand for 5 consecutive days and nights.