Relationships Between Affected-Leg Motor Impairment, Postural Asymmetry, and Impaired Body Sway Control After Unilateral Supratentorial Stroke

Background. The relationships between motor impairment of the affected leg, postural control asymmetry, and impaired body sway control after stroke are not well understood. Objective. To examine the relationship between motor impairment of the affected leg and reduced contribution of this leg to body sway control (ie, dynamic control asymmetry [DCA]) and to determine the relationships between impaired body sway control, DCA, and weight-bearing asymmetry (WBA). Methods. We assessed quiet-standing balance with eyes open in 70 persons with a unilateral supratentorial chronic stroke using 2 force plates. Center-of-pressure (COP) velocity was calculated for both feet together in the anteroposterior (AP) and mediolateral (ML) directions as a measure of body sway control. Bilateral AP COP velocities were used to calculate an index for DCA and weight borne on each side to calculate WBA. Fugl-Meyer assessment of the lower extremity (FMA-LE; range: 0-28) served as a measure of affected-leg motor impairment. Results. All participants with FMA-LE <24 showed pronounced DCA, but this was also true for 21% of those with FMA ⩾24. Higher DCA values were related to more WBA (r(s) = 0.496; P < .001), and less ML sway control (r(s) = 0.268; P = .025). AP sway control was not significantly related to either DCA or WBA. Conclusions. Even clinically well-recovered stroke survivors with (near) maximal FMA-LE scores may show clear postural asymmetry in terms of the relative contribution of the affected leg to body sway control. WBA seems to be an effective compensatory mechanism to optimize the contribution of the less-affected leg to balance, particularly in the AP direction.