Aberrant neural circuits in malformations of cortical development and focal epilepsy.

Malformations of cortical development (MCD) account for a high proportion of medically resistant partial seizures in children and figure prominently in pediatric surgical series. In contrast to the results of epilepsy surgery for postnatally acquired lesions, seizure freedom in patients with MCD is less certain owing to difficulties in defining the epileptic zone, and fully excising the epileptogenic cortex. The authors present evidence that, compared with postnatally acquired lesions such as those due to tumors or trauma, focal epileptogenesis associated with MCD is best conceptualized as a disorder of widespread and patchy disturbance of cortical networks. This developmental perspective implies that the epileptogenic region in MCD is rarely discrete even in patients with focal anatomic lesions, and may include remote cortical or subcortical areas. Preoperative investigative protocols based on this model have improved surgical results, but outcome remains far from optimal and further progress in understanding the complex developmentally based features of MCD is required.