Evidence for a disorder of locomotor timing in Huntington's disease.

Disturbances of walking have been described in people with Huntington's disease (HD), although the nature of the deficits have not yet been well defined. The purpose of this investigation was to determine whether people with HD have a deficit in the regulation of footstep timing during walking. The footstep patterns of 30 people with HD and 30 matched comparisons were measured at self-selected slow, preferred, and fast speeds. Subjects were also instructed to match their footsteps to auditory metronome cues set at 80 and 120 beats per minute. Gait speed, cadence, stride length, and double limb support as a percentage of the gait cycle were measured using a computerized foot-switch system. People with HD demonstrated a disorder in their ability to regulate cadence, manifest as a reduced step frequency when walking at preferred speed and when required to increase their speed. For all walking conditions, people with HD had increased variability of footstep cadence. They also had difficulty synchronizing their footstep timing to an auditory cue. For all walking conditions, people with HD had reduced stride length. Thus, in HD, there is a disorder in the regulation of footstep timing, with increased variability, a restricted cadence range, difficulty synchronizing footsteps to an auditory cue and reduced stride length. The exact neural correlates of this timing disorder are yet to be determined.