Ipsilateral motor cortex activation by unaffected hand movements in patients with cerebral infarct

Many studies have reported that stroke patients can be accompanied by motor deficit of the unaffected extremities as well as the affected extremities. This suggests that neural control of motor function of unaffected extremities might be changed following stroke. However, very little is known about this topic. Using functional MRI (fMRI), we investigated changes in neural control of motor function of the unaffected hand in hemiparetic patients with cerebral infarct. Thirty-five hemiparetic stroke patients were recruited for this study. fMRI was performed at 1.5T during either affected or unaffected hand flexion-extension movements. We evaluated motor function of the affected upper extremity using the upper Motricity index (UMI) and the medical research council (MRC) scale for finger extensor. From fMRI, LI (laterality index) was calculated for assessment of relative activity in the ipsilateral versus the contralateral primary sensorimotor cortex. Positive correlation between LIs was observed during affected and unaffected hand movements (r=0.670, p=0.000). LI of unaffected hand movements was also correlated with the affected UMI (r=0.408, p=0.015) and MRC of the affected hand extensor (r=0.362, p=0.033). We demonstrated that the ipsilateral (affected) motor cortex was recruited by unaffected hand movements in proportion to poor motor function of the affected upper extremity.