Augmented reality turning cues to reduce freezing of gait in Parkinson’s disease
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Background: Freezing of gait (FOG) – defined as: brief, episodic absence or marked reduction of forward progression of the feet, despite the intention to walk – is a debilitating motor symptom that occurs in up to 60% of patients with Parkinson’s disease (PD) . Turning in place is arguably the most frequent trigger for FOG. External cueing, using visual or auditory cues, has shown to be a valuable strategy to prevent or overcome FOG. In this study we have used smart glasses for interactive visual cueing in augmented reality (AR) during turning in place. The cues consist of targets surrounding the user and a Pacman figure, whose movement is linked to head rotation. The targets can be interactively reached with the Pacman figure by turning around. Our cueing system is intended to promote goal-directed movement, to direct the attention to gait and to provide spatial reference for enforcing appropriate amplitude generation. Aims: We investigated the effectivity of our AR visual cueing system in reducing FOG severity and improving gait performance. Furthermore, we assessed the relative effectivity of our AR cueing system, compared to conventional auditory cueing. Methods: We tested 8 subjects with PD and regular FOG during ‘end of dose’ state. Subjects performed 180 degrees turns around the axis during different cueing conditions: visual, auditory or no cueing. FOG severity was rated by an expert clinician using video recordings, and gait performance was measured using an inertial measurement system. Our endpoints were: number of FOG episodes, time spent freezing, stride length, step height, turn time, cadence and stride time variability. Results: We found no significant difference in the number of FOG episodes, nor in the percentage of time spent freezing, between cueing conditions in the tested group of patients. We observed large between-subject variability in the effects of different cueing conditions on FOG severity. Step height was significantly decreased in the visual cueing condition when compared to other conditions. There were no significant differences in the median turn time, stride length or cadence between different cueing conditions. The variability of stride time was significantly reduced in the auditory cueing condition, compared to the control and visual cueing conditions. Conclusion: Our AR visual cueing system did not significantly reduce FOG severity. On the contrary, rather than improving gait performance, it significantly decreased the step height. Auditory cueing significantly reduced the variability of stride time, but was, unexpectedly, ineffective in reducing FOG severity and improving other gait parameters. These findings may either reflect some primary incompatibility of external cueing for turning in place, or limitations to our cueing system. Further and larger-scale research is required to investigate effectivity of AR visual cueing for reduction of FOG severity and improvement of gait performance during turning in place. Points of improvement in future cue designs may include the use of stimuli that provide spatial information that is directly linked to gait execution; provide an explicit goal to reduce required action selection processing; and minimize distraction. Implementation of external cueing for ambulant treatment of FOG during turning in place, may require a personalized approach.
Faculteit der Sociale Wetenschappen