Focal cortical dysplasia (FCD) is a common finding in epilepsy surgery in pediatric patients. Children with intractable epilepsy would have extensive tests to identify the cause of epilepsy; this includes MR brain, video EEG and magnetoencephalography (MEG). The white matter next to FCD is frequently found to be abnormal on pathology. Diffusion tensor imaging (DTI) can be used to study the abnormal white matter and the area that often extends beyond the area that is visible.