Researchers at the Northern California Epilepsy Center and University of California, San Francisco, conducted a retrospective review of 143 patients with malformations of cortical development (MCD) who underwent resection surgery for medically refractory epilepsy. Median age of seizure onset was 7 years (range, 0-55 years) with 123 (86%) having childhood onset (<18 years). Complex partial seizures were most common (47.5%) followed by generalized tonic-clonic (23%). Preoperative MRI, classified according to a new MCD classification, included subcortical T2/FLAIR abnormality (46.1%), blurring of gray-white junction (26.6%), cortical thickening (17.2%), and mesiotemporal sclerosis (16.1%). ECoG revealed epileptiform activity in 111 patients, focal in 67.7%. Total resection of abnormal area was achieved in 68.1%. Heterotopia were present in 35%, and neuronal dysplasias in 33.3%. According to the Barkovich classification for MCD, 22% were class I (abnormal neuronal and glial proliferation), 10% class II (abnormal migration), 65% class III (abnormal organization), and 3% class IV (abnormal development). Class I patients had better outcome than class II or III. Complete resection of ECoG and anatomic abnormalities was the main independent predictor of seizure freedom. Other favorable predictors were smaller lesions and locally confined ECoG abnormalities. Long-term follow-up demonstrated seizure control in 72% at 2 years, 65% at 5 years, and 67% at 10 years. 
COMMENT. MR imaging and intracranial ECoG recordings are essential determinants of outcome of patients with MCD and medically intractable epilepsy. Neuronal proliferation pathology carries a better prognosis than abnormalities of cortical migration or organization. Surgery can result in 67% long-term seizure freedom.