The role of the contralesional motor cortex for motor recovery in the early days after stroke assessed with longitudinal FMRI.

Stroke may trigger a number of cellular and molecular events in perilesional and remote brain regions enabling cortical reorganization and recovery of function. We here investigated the pattern and time course of acute stroke-induced changes in motor system activity during motor recovery using functional magnetic resonance imaging. Hand movement-related neural activity was assessed in 11 acute stroke patients scanned 3 times during the first 2 weeks starting within 72 h after symptom onset. A motor recovery score was computed based on the action research arm test and the maximum grip force. Increases of activity in primary motor cortex, premotor cortex (dorsal and ventral), and supplementary motor area in both hemispheres significantly correlated with behavioral recovery. These longitudinal changes depended upon the degree of initial motor impairment: Patients with mild deficits did not differ from healthy subjects. In contrast, patients with severe deficits were characterized by a global reduction of task-related activity, followed by increases in ipsilesional as well as contralesional motor areas. The finding that the gradually increasing activity in contralesional primary motor and premotor cortex correlated with improved functional recovery in severely affected patients indicates early cortical reorganization supporting motor function of the affected hand.