Modeling freezing of gait in Parkinson's disease with a virtual reality paradigm.

Freezing of gait is a paroxysmal and disabling symptom that commonly affects patients in the latter stages of Parkinson's disease, however the intermittent nature of this symptom makes it difficult to study in the clinical setting. Our research group has previously reported a correlation between self-reported freezing of gait symptoms and performance on a seated virtual reality gait task. In this study, we sought to determine whether behavioral measures recorded on this task were correlated with actual clinical measures of freezing of gait recorded in a cohort of 38 Parkinson's disease patients whilst in their clinically defined 'off' state. Firstly, patients with freezing of gait had a significantly larger frequency of spontaneous motor arrests recorded on the virtual reality gait task than 'non-freezers'. In addition, in those 24 patients with clinically proven freezing of gait, the number and percentage of time spent with freezing on the virtual reality task were both moderately correlated with the duration of freezing of gait recorded on the timed up-and-go tasks. These findings suggest that the freezing behavior observed during a virtual reality gait task may share similar neural substrates to freezing of gait. Such a relationship could offer a potential avenue for modeling the phenomenon of freezing of gait in Parkinson's disease, allowing for the exploration of the neural correlates of freezing.