An fMRI, DTI and Neurophysiological Examination of Atypical Organization of Motor Cortex in Ipsilesional Hemisphere Following Post-Stroke Recovery.

We report a 61-year-old woman who developed left hemiparesis following a right frontal stroke. She underwent rehabilitation and regained function of the left side of her body. Three years after her first stroke, she developed a large left subdural hematoma and again presented with left hemiparesis. Prior to the cranioplasty, an fMRI scan involving left and right hand movement, arm movement, and foot peddling were conducted in order to determine whether the patient showed ipsilateral activation for the motor tasks, thus explaining the left hemiparesis following the left subdural hematoma. Diffusion tensor imaging (DTI) tractography was also collected to visualize the motor and sensory tracts. The fMRI results revealed activation in the expected contralateral left primary motor cortex (M1) for the right-sided motor tasks, and bilateral M1 activation for the left-sided motor tasks. Intraoperative neurophysiology confirmed these findings, whereby electromyography revealed left-sided (i.e., ipsilateral) responses for four of the five electrode locations. The DTI results indicated that the corticospinal tracts and spinothalamic tracts were within normal limits and showed no displacement or disorganization. These results suggest that there may have been reorganization of the M1 following her initial stroke, and that the left hemisphere may have become involved in moving the left side of the body thereby leading to left hemiparesis following the left subdural hematoma. The findings suggest that cortical reorganization may occur in stroke patients recovering from hemiparesis, and specifically, that components of motor processing subserved by M1 may be taken over by ipsilateral regions.

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