Effect of cue timing and modality on gait initiation in Parkinson's disease with freezing of gait

Abstract Objective To examine the effects of cue timing, across three sensory modalities, on anticipatory postural adjustments (APAs) during gait initiation in people with Parkinson’s disease (PD). Design Observational study. Setting Biomechanics research laboratory. Participants Twenty-five individuals with idiopathic PD (11 with freezing of gait, FOG) were studied in the off-levodopa state (12-hour overnight withdrawal). Interventions Gait initiation was tested without cueing (self-initiated) and with three cue timing protocols: fixed delay (3 s), random delay (4-12 s) and countdown (3-2-1-go, 1 s intervals) across three sensory modalities (acoustic, visual and vibrotactile). Main Outcome Measures The incidence and spatiotemporal characteristics of APAs during gait initiation were analyzed, including vertical ground reaction forces and center of pressure. Results All cue timings and modalities increased the incidence and amplitude of APAs compared to self-initiated stepping. Acoustic and visual cues, but not vibrotactile stimulation, improved the timing of APAs. Fixed delay or countdown timing protocols were more effective at decreasing APA durations compared to random delay cues. Cue-evoked improvements in APA timing, but not amplitude, correlated with the level of impairment during self-initiated gait. Cues did not improve the late push-off phase in the FOG group. Conclusions External cueing improves gait initiation in PD regardless of cue timing, modality, or clinical phenotype (with and without FOG). Acoustic or visual cueing with predictive timing provided the greatest improvements in gait initiation thus these protocols may provide the best outcomes when applied by caregivers or devices.