Dynamic Postural Control in Parkinson’s Disease During Gesture Controlled Virtual Reality
Postural instability in individuals diagnosed with Parkinson’s disease (PD) is a debilitating and difficult to treat symptom. It is highly associated with falls and decreased quality of life. Recently, Virtual Reality (VR) applications have emerged as a potential tool for both evaluation and treatment of balance disorders in a variety of population such as Stroke and Spinal Cord Injury.
Objective: To determine the effects of various gesture-controlled VR applications on different postural control parameters in PD. Subject Population: Volunteers diagnosed with moderate to severe Idiopathic Parkinson’s Disease (PD) (n=5) and their age matched controls (n=8).
Methods: In this experimental study, each volunteer was tasked with three trials of Quiet Stance and 5 different VR applications. The ground reaction forces (GRF’s) were measured using a strain gauge force platform and was subsequently used to calculate Center of Pressure (COP). Further, this COP was used to extract seven variables for measuring postural stability: Center of Pressure velocities in the medio-lateral and antero-posterior direction (i.e., COPv_ML and COPv_AP), minimum Time to boundary (TtB_min), integrated Time to Boundary (iTtB), area of 95% of Confidence Ellipse (CE), Residual of postural control i.e., COP minus Center of Mass (COM) in the medio-lateral and antero-posterior direction (i.e., COPCOM_ML and COPCOM_AP) respectively.
Results: COPv_ML and iTtB were significantly different for the two groups (p <.05). A strong effect of different VR applications was also observed (p<.001).
Overall, the PD group performed less effectively to challenges offered by dynamic VR activities as evidenced by low COP velocities, higher time to boundary values, lower confidence ellipse and lower COPCOM values.
Conclusion: Results suggest that Individual’s with PD “over constrain” their posture due to fear of falling and adopt a “posture-first strategy” when confronted with complex dynamic activities. While this reduces chances of falls, it may also reduce their chances to adapt and perform well to changing dynamic situations faced during day-to-day life and may indirectly increase chances of falls. Training of such responses in a closed, modifiable environment may help in training the cortical responses. This study also shows that medio-lateral (ML) stability when measured through COP velocity is a good indicator of postural stability. In addition, it suggests that iTtB is a very sensitive indicator of postural stability for dynamic VR activities.
Potential impacts & next steps: This pilot study tested the feasibility of the protocol and use of such VR activities for future longitudinal studies to determine role of gesture controlled VR activities in improving postural stability in PD.