Postural responses of adults with cerebral palsy to combined base of support and visual field rotation

We employed a virtual environment to examine the postural behaviors of adults with cerebral palsy (CP). Four adults with CP (22–32 yrs) and 9 healthy adults (21–27 yrs) were tested in a Rod and Frame protocol. They then stood quietly on a platform within a 3-wall virtual environment. The platform was tilted 3° into dorsiflexion while in the dark or with pitch up and down visual field rotations at 30 and 45 °/sec. While the visual field rotated, the platform was held tilted for 30 sec and then slowly returned to a neutral position over 30 sec. Trials with the platform stationary were performed with the same visual field rotations. Center of pressure (CoP) was recorded and center of mass (CoM) was calculated. Angular deviations from the Rod and Frame test were larger in adults with CP suggesting that they are visually dependent. Adults with CP had difficulty maintaining balance when standing on a stationary platform with pitch upward rotation. When the platform tilted with visual field rotation, adults with CP took longer to stabilize themselves after the tilt and had larger CoM oscillations over the trial compared to dark. Plots of CoP revealed that side-to-side CoP increased on both a stationary and tilted platform when visual flow was presented suggesting that adults with CP are unstable with visual flow. Two adults with CP were wheelchair users and they exhibited even larger CoP RMS values indicating greater instability in adults with impaired ambulatory function.