Dexterity is impaired at both hands following unilateral subcortical middle cerebral artery stroke

Dexterity was investigated in right-handed subjects in the subacute phase of a first unilateral subcortical middle cerebral artery stroke affecting the left or right hemisphere and right-handed healthy subjects. Dexterity was quantified at both hands by kinematic recordings of finger and hand tapping, a reach-to-grasp movement, quantitative analysis of grip forces in a grasp-lift task and clinical rating scales. Stroke subjects exhibited significant deficits in timing and coordination of tapping movements at both the contralesional and ipsilesional hands, irrespective of the hemisphere affected. Likely for the reach-to-grasp and grasp-lift movements a bilateral impairment was found in stroke subjects. In particular, slowing of hand transport towards the object, deficient timing and scaling of grasp formation, discoordination between grip and lift forces and inefficient scaling of grip forces were observed. The severity of impairment was independent of the hemisphere affected and evident for both the reach (involving more proximal muscles of the arm) and grasp (involving more distal muscles of the arm and hand) components of the task. Strong correlations were found between clinical scores of hand function and loss of sensibility with the deficits in timing, coordination and efficiency of movement of the contralesional and ipsilesional hand. These data provide evidence that dexterity is impaired at both hands after subcortical middle cerebral artery stroke.