Effect of Cue Timing and Modality on Gait Initiation in Parkinson Disease With Freezing of Gait

Abstract

Objective: To examine the effects of cue timing, across 3 sensory modalities, on anticipatory postural adjustments (APAs) during gait initiation in people with Parkinson disease (PD).

Design: Observational study.

Setting: Biomechanics research laboratory.

Participants: Individuals with idiopathic PD (N=25; 11 with freezing of gait [FOG]) were studied in the off-medication state (12-h overnight withdrawal).

Interventions: Gait initiation was tested without cueing (self-initiated) and with 3 cue timing protocols: fixed delay (3s), random delay (4-12s), and countdown (3-2-1-go, 1-s intervals) across 3 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 with 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 than 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; therefore, these protocols may provide the best outcomes when applied by caregivers or devices.

Keywords: Cues; Freezing; Gait; Parkinson disease; Rehabilitation.

Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Figure 1. A: Paradigm for external cued and self-initiated protocols Figure 1. B: Examples of anticipatory postural adjustments (APAs) during an acoustically cued and a self-initiated gait initiation trial in a participant with Parkinson’s disease. The vertical arrows indicate the time points of the onset, peak and toe-off in the vertical ground reaction forces (GRF) on the step and stance legs and the onset and peak of the initial center of pressure excursions in the mediolateral (CoPml) and anteroposterior (CoPap) directions. Note the absence of an APA in the self-initiated example (no initial peak loading of the step leg, no peak unloading of the stance leg, no lateral or initial posterior excursions in the CoP).

Figure 2

A: The average spatiotemporal characteristics of the initial peak posterior center of pressure excursions (CoPap1) during step initiation in self-initiated and visually cued conditions. The effect of cue timing only affected the duration, not the magnitude of peak CoPap1 in cued condition. Error bar indicates ± one SE. * indicates significant difference after Bonferroni adjustment. B: Correlation analyses between the change in performance induced by the cue (cued - self-initiated) and performance during the self-initiated condition in the time to step leg peak vertical GRF (top row) and peak amplitude of the step leg vertical GRF (bottom row) for acoustic (left column), visual (middle column) and vibrotactile (right column) cues. There were strong negative correlations between improvements in the timing of APAs evoked by cues (negative change values denoting decreased durations with a cue) and deficits in timing present during self-initiated stepping. In contrast, correlations between cued-evoked changes in peak amplitude and self-initiated amplitude were mostly non-significant and weak. Line and marker color: blue, fixed delay; green, random delay; red, countdown. Abbreviation: NS, non-significant.