Cortical dysplasia is the most common etiology in children and the third most frequent finding in adults undergoing
epilepsy neurosurgery. The new International League Against
Epilepsy (ILAE) classification grades isolated
cortical dysplasia into mild type I (cortical dyslamination), severe type II (dyslamination plus dysmorphic neurons and balloon cells), and dysplasia associated with other epileptogenic lesions (type III). Multilobar type II lesions present at an earlier age and with more severe
epilepsy compared with focal type I abnormalities, often in the temporal lobe, and these findings are reflected in types and age of operations for
cortical dysplasia. Presurgical evaluation of patients with
epilepsy from
cortical dysplasia can be challenging. Interictal and ictal scalp electroencephalography (EEG) accurately localizes
cortical dysplasia with 50-66% accuracy. Structural magnetic resonance imaging (MRI) is negative in roughly 30% of cases, most often linked with mild type I cases. FDG-PET can be 80-90% accurate, but is not 100% sensitive. Chronic intracranial
electrodes are used in about 50% of cases with
cortical dysplasia, but often do not capture restricted ictal-onset zones. About 60% of patients with
cortical dysplasia are seizure free after
epilepsy neurosurgery, with much higher rates of becoming seizure free with complete (80%) compared with incomplete (20%) resections. The most common reason for incomplete resection is the risk of an unacceptable
neurologic deficit. Future challenges include better tools in identifying subtle forms of type I
cortical dysplasia, and development of adjunctive treatments from basic research for those undergoing incomplete resections.