Targeting dopa-sensitive and dopa-resistant gait dysfunction in Parkinson's disease: selective responses to internal and external cues.

BACKGROUND Independence of certain gait characteristics from dopamine replacement therapies highlights its complex pathophysiology in Parkinson's disease (PD). We explored the effect of two different cue strategies on gait characteristics in relation to their response to dopaminergic medications. PATIENTS AND METHODS Fifty people with PD (age 69.22 ± 6.6 years) were studied. Participants walked with and without cues presented in a randomized order. Cue strategies were: (1) internal cue (attention to increase step length) and (2) external cue (auditory cue with instruction to take large step to the beat). Testing was carried out two times at home (on and off medication). Gait was measured using a Stride Analyzer (B&L Engineering). Gait outcomes were walking speed, stride length, step frequency, and coefficient of variation (CV) of stride time and double limb support duration (DLS). RESULTS Walking speed, stride length, and stride time CV improved on dopaminergic medications, whereas step frequency and DLS CV did not. Internal and external cues increased stride time and walking speed (on and off dopaminergic medications). Only the external cue significantly improved stride time CV and DLS CV, whereas the internal cue had no effect (on and off dopaminergic medications). CONCLUSIONS Internal and external cues selectively modify gait characteristics in relation to the type of gait disturbance and its dopa-responsiveness. Although internal (attention) and external cues target dopaminergic gait dysfunction (stride length), only external cues target stride to stride fluctuations in gait. Despite an overlap with dopaminergic pathways, external cues may effectively address nondopaminergic gait dysfunction and potentially increase mobility and reduce gait instability and falls.