MRI features were correlated with postsurgical seizure outcome in patients
with hemispheric malformations of cortical development (MCD). After functio
nal hemispherectomy, 5 of 6 patients (83%) with hemimegalencephaly had pers
istent, although markedly improved, seizures; 5 of 6 patients (83%) with re
lative preservation of part of one lobe or atrophy were seizure free. Hemim
egalencephaly and other types of hemispheric MCD appear to differ in progno
sis for freedom from seizures after functional hemispherectomy.