The results of surgical treatment for malformations of cortical development (MCD) causing refractory epilepsy are reviewed from the Institute of Neurology, Queen Square, London, UK. Forty one percent of patients with MCD, especially those with focal cortical dysplasia (FCD), are seizure-free over a 2-year follow-up after resective surgery. A proportion may also be helped significantly. Different types of MCD have different sequelae, some including FCD and heterotopia being intrinsically epileptogenic. For polymicrogyria and schizencephaly, the visualized abnormalities are not always the epileptogenic zone. Preoperative EEG, MRI, PET, SPECT, functional MRI and magnetoencephalography, with quantitative analysis, are recommended when possible. Extralesional regions should be included in the studies. 
COMMENT. A 40% post-surgical rate of seizure-free patients with MCD and focal cortical dysplasia is considerably lower than the 70% of patients with cessation of seizures following resection for hippocampal sclerosis. Occult MCD in addition to overt MCD might account for the relatively poor seizure outcome.