Challenges in the surgical treatment of epilepsy patients with cortical dysplasia

Cortical dysplasia (CD) is the most common malformation of cortical development in epilepsy surgery patients. Patients with mild Palmini type I CD represent about 50% of the surgical cases, and these lesions tend to occur most often in the temporal lobe, often associated with hippocampal sclerosis. By comparison, patients with severe type II CD present at younger ages, often with multilobar extratemporal lesions, and more aggressive seizures. The presurgical evaluation in CD patients can be challenging, as no single test is 100% accurate. Based on retrospective cohort studies, the accuracy of investigations are: interictal scalp electroencephalography (EEG), 50%; ictal scalp EEG, 65%; magnetic resonance imaging (MRI), 66%; fluorodeoxyglucose-positron emission tomography (FDG-PET), 81%; and ictal single photon emission computed tomography (SPECT), 57%. Intracranial electrodes are used in about 50% of patients with CD. Contemporary series report that 62% of patients with CD are seizure free after resective neurosurgery, with higher rates for complete (77%) compared with incomplete (20%) removal of the lesion. Morbidity (<3%) and mortality (0.2%) are low for patients with CD undergoing epilepsy neurosurgery. Future challenges include the noninvasive identification of patients with CD with 100% accuracy, evaluation of long-term outcomes in surgical patients, and devising new treatments based on a better understanding of the neurobiology leading to seizures in CD tissue.