Neuromotor control of walking balance in individuals with cerebral palsy

Individuals with cerebral palsy (CP) have deficits in processing of
somatosensory and proprioceptive information. To compensate for these
deficits, they tend to rely on vision over proprioception in single plane
upper and lower limb movements and in standing. It is not known whether
this also applies to walking, an activity where the threat to balance is
higher. Through this study, we used visual perturbations to understand how
individuals with and without CP integrate visual input for walking balance
control. Additionally, we probed the balance mechanisms driving the
responses to the visual perturbations. More specifically, we investigated
differences in the use of ankle roll response i.e. the use of ankle
inversion, and the foot placement response, i.e., stepping in the
direction of perceived fall. Thirty-four participants (17 CP, 17 age-and
sex-matched typically developing controls or TD) were recruited.
Participants walked on a self-paced treadmill in a virtual reality
environment. Intermittently, the virtual scene was rotated in the frontal
plane to induce the sensation of a sideways fall. Our results showed that
compared to their TD peers, the overall body sway in response to the
visual perturbations was magnified and delayed in CP group, implying that
they were more affected by changes in visual cues and relied more so on
visual information for walking balance control. Also, the CP group showed
a lack of ankle response, through a significantly reduced ankle inversion
on the affected side compared to the TD group. The CP group showed a
higher foot placement response compared to the TD group immediately
following the visual perturbations. Thus, individuals with CP showed a
dominant proximal foot placement strategy and diminished ankle roll
response, suggestive of a reliance on proximal over distal control of
walking balance in individuals with CP.