Understanding Adaptive Motor Control of the Paretic Upper Limb Early Poststroke

Abstract

Background. During upper limb motor recovery after stroke, the greatest improvements occur typically in the first 5 weeks poststroke. It is unclear what patients learn during this early phase of recovery. Objective. To investigate the hypothesis that, early poststroke, patients learn to master the degrees of freedom in the paretic upper limb as reflected by dissociated shoulder and elbow movements during reach-to-grasp. Methods. Thirty-one patients with a first-ever ischemic stroke were included. Repeated 3-dimensional kinematic measurements were conducted at 14, 25, 38, 57, 92, and 189 days poststroke. Trunk, shoulder, elbow, and wrist rotations were measured during a reach-to-grasp task. Using principal component analysis the longitudinal changes in dissociated upper limb movements during reach-to-grasp were investigated. Twelve healthy subjects were included for comparison. Results. The main coordination pattern during reach-to-grasp in patients with stroke and healthy subjects consisted mostly of horizontal shoulder adduction and elbow extension. The standard deviation of this main pattern increased over time, with the largest increase in the first 5 weeks poststroke ( F = 5.5, P < .001), but remained smaller than in healthy individuals. The standard deviation increased by 0.46° per day between 14 and 38 days and tapered off to 0.05° per day between 38 and 189 days poststroke. Conclusions. Our results suggest that restitution of motor control by dissociation of shoulder and elbow movements occurs mainly early poststroke. However, compared with healthy adults, most patients did not achieve fully dissociated upper limb movements at 26 weeks poststroke, suggesting that upper limb motor control after stroke remains adaptive.