Reorganization of sensorimotor functions pre and post hemispherectomy in children with refractory epilepsy

grantor: University of TorontoThe studies presented in this manuscript explore the processes of developmental cortical plasticity in children pre and post hemispherectomy. Evaluations at the structural, physiological, clinical and disability levels are conducted for the children involved. Functional magnetic resonance imaging was used to visualize novel or unmasked cortical areas in the remaining hemisphere, suggesting inter-hemispheric transfer of sensorimotor functions. We have shown that associated cortical sensorimotor areas may be sufficient to express residual gross and fine motor functions. Individual variations in the recruitment of these cortical areas may suggest regionalization of brain plasticity. Progressive shifting or unmasking of cortical activations in the preoperative children may be related to the development of the disease and will influence the timing of surgery. The Gross Motor Function Measure and the Quality of Upper Extremity Skills Test were used to provide quantitative data in detailed domains of gross motor and fine motor functions. We have shown that children with congenital disease are more impaired postoperatively than children with acquired disease. We suggest that a normal preoperative period of development may be essential to the recovery of gross and fine motor functions after hemispherectomy. The Activity Scale for Kids and the Pediatric Evaluation-of Disability inventory were used to provide quantitative data in detailed domains of independence. We have shown comparable levels of disability between the children pre and post hemispherectomy pointing at the impact of an active seizure disorder The determination of significant predictors of clinical and disability outcomes--such as age at surgery and interval between seizure onset and surgery--has helped us identify a potentially optimum timing of surgery. We have shown that a child who is 5 years of age and older or who has waited at least 2 years between seizure onset and surgery will potentially perform better in gross motor skiffs and be less physically disabled. We also strongly cautioned the application of these findings to clinical practice as exceptions to the statistically significant results are noticed. The combination of neuroimaging, gross motor function, fine motor function and disability measures have and will contribute to further our understanding of child's development and brain plasticity.Ph.D