Direction-specific Disruption of Paretic Arm Movement in Post-stroke Patients.

Objective: This study aimed to characterize reaching movements of the paretic arm in different directions within the reachable workspace in post-stroke patients.

Methods: A total of 12 post-stroke patients participated in this study. Each held a ball with a tracking marker and performed back-and-forth reaching movements from near the middle of the body to one of two targets in front of them located on the ipsilateral and contralateral sides of the arm performing the movement. We recorded and analyzed the trajectories of the tracking marker. The stability of arm movements was evaluated using areas and minimum Feret diameters to assess the trajectories of both the paretic and non-paretic arms. The speed of the arm movement was also calculated.

Results: For the paretic arm, contralateral movement was more impaired than ipsilateral movement, whereas for the non-paretic arm, no difference was observed between the directions. The maximum speed of the contralateral movement was significantly slower than that of the ipsilateral movement in both the paretic and non-paretic arms.

Conclusion: The paretic arm shows direction-specific instability in movement toward the contralateral side of the arm.