Paretic and Non-Paretic Arm Motor Deficit and Recovery as a Function of Lesion Lateralization and Paresis Severity: A Biomechanical Study

— The aim of this research was to study the dependence of poststroke motor impairments of paretic and non-paretic arm on lesion lateralization, and paresis severity. The influence of lesion lateralization and paresis severity on the recovery of motor functions (MFs) after rehabilitation using a hand exoskeleton controlled by a brain–computer interface was also investigated. The study included 24 patients, 12 with left and 12 with right hemispheric lesions. Each group included six patients with moderate paresis and six patients with severe paresis. Isolated movements in the joints of paretic and non-paretic arms were used as motor tests performed before and after the course of rehabilitation. Joint torque and movement isolation degree were used to assess MFs. It was shown that the joint torques of the non-paretic arm were greater in the case of left hemispheric lesions, characterized by more pronounced asymmetry of joint torques than in right hemispheric lesions. This might be due to a greater imbalance in the activity of hemispheres. The effectiveness of rehabilitation was manifested in: (1) an increase in joint torques in both paretic and non-paretic arms and (2) an increase in the symmetry of biomechanical parameters of paretic and non-paretic arms, potentially indicating the restoration of balance in the hemispheric activity. The biomechanical analysis of isolated movements suggested the pronation–supination movement in a vertical forearm position as a sensitive indicator of MF recovery after stroke.