Effect of optokinetic stimulation on weight-bearing shift in standing and sitting positions in stroke patients

Abstract

Background: Patients with hemiplegia after stroke tend to bear weight on the non-paretic side and exhibit large postural sway during static standing and walking, which may increase their risk of falls. Improvement of the sitting posture balance in the early phase of rehabilitation by adjusting weight-bearing would minimize the risk of falls as early rehabilitation reportedly improves walking ability and prevents falls in later phases of rehabilitation or at discharge.

Aim: This study aimed to evaluate the effect of optokinetic stimulation (OKS) on shift of the weight-bearing (displacement of the center of pressure [CoP]) in patients with hemiplegia who are incapable of independent standing.

Design: Quasi-experimental, cross-sectional study.

Setting: Rehabilitation hospital.

Population: Patients with hemiplegia in the subacute phase after stroke (N.=37).

Methods: Standing and sitting balance tests were performed during OKS projected onto a screen. For OKS, a pattern of random dots was presented, which continuously moved in horizontal or torsional directions during both static standing and sitting conditions. Postural sway was assessed during standing and sitting by measuring the sway path, sway area, sway velocity, and mean displacement of CoP. The magnitude of the lateral change in CoP as an indicator of the weight-bearing shift was evaluated by subtraction of the mean CoP of the right-left axis component in the stationary condition from the mean CoP sway during OKS.

Results: OKS induced a unilateral change of the mean CoP position in patients during both, sitting and static standing, indicating that OKS can shift the weight-bearing in patients after stroke, irrespective of the posture condition. Moreover, the same OKS approach evoked an analogous shift in patients with more severe symptoms, with impairment in independent standing.

Conclusions: OKS could induce a significant shift in weight balance in patients with hemiplegia after stroke who are incapable of independent standing, suggesting that the OKS approach can be applied to a broader spectrum of patients, including those with more severe symptoms.

Clinical rehabilitation impact: OKS approach would improve exercise training in the early phase of rehabilitation of patients with hemiplegia after stroke.