Preoperative evaluation in children for epilepsy surgery

Epilepsy surgery has proven to be a valuable therapy in the management of pharmacoresistant seizures in childhood. The goal of surgery is to identify and safely remove epileptogenic tissue and render the child seizure free. This is accomplished through intensive multimodality preoperative investigations designed to accurately localize the epileptogenic region and anatomically characterize functionally critical cortical areas subserving language, movement, and vision. Seizure semiology must be characterized and correlated with the results of electroencephalograhy (EEG) investigations and anatomic and functional imaging. Most pediatric epilepsy surgery centers perform video-EEG and magnetic resonance imaging (MRI). Positron emission tomography and ictal single photon emission computed tomography are also obtained frequently. Postprocessing of the MRI utilizing techniques such as voxel-based three-dimensional analysis has shown exceptional promise for detecting subtle malformative lesions involving the cortex and subcortical white matter. All of these initial investigations can be performed noninvasively and reviewed by a multidisciplinary team. Patients with a poorly delineated epileptogenic zone or seizures that are thought to be arising in or near critical cortex often require chronic extraoperative implantation of subdural or depth electrodes. Newer investigative modalities and further refinement of existing techniques hold promise for improved candidate selection and cortical localization.