Cortical activation in patients with functional hemispherectomy

Functional hemispherectomy, a safe and effective therapeutical procedure in medically intractable epilepsy, offers the chance to investigate a strictl y unilateral cortical activation in ipsilateral limb movement. We assessed the pattern of cortical activation in a group of patients following functio nal hemispherectomy. We measured regional cerebral blood flow (rCBF) in 6 p atients postoperatively and 6 normal subjects with positron emission tomogr aphy using (15)[O]H2O as a tracer. Brain activation was achieved by passive elbow movements of the affected arm. Analysis of group results and between -group comparisons were performed with statistical parametric mapping, (SPM 96). In normal subjects brain activation was found contralaterally in the c ranial sensorimotor cortex and the supplementary motor area and ipsilateral ly in the inferior parietal cortex. In patients significant rCBF increases were found in the inferior parietal cortex, caudal sensorimotor cortex and the supplementary motor area ipsilaterally. The activation was weaker than in normal subjects. Compared with normal subjects patients showed additiona l activation in the premotor cortex, caudal sensorimotor cortex and the inf erior parietal cortex of the remaining hemisphere. Less activation compared with normal subjects was found in the cranial sensorimotor cortex and the supplementary motor area. A functional network connecting the inferior pari etal cortex, premotor cortex and the supplementary motor area as well as th e existence of ipsilateral projections originating from these regions may e xplain why these areas are predominantly involved in reorganization confine d to a single hemisphere.