Charts of 111 patients, ages 2 months to 20 years, who underwent hemidecortication for intractable unihemispheric epilepsy in the period 1975-2001 were reviewed at Johns Hopkins Hospital. The average time from seizure onset to operation was 3.6 years. Follow-up ranged from 3 months to 22 years (3 died in the perioperative period, 2 died later due to seizures, and 3 were lost to follow-up). Seizures were controlled in 65%, 21% had occasional seizures, and 14% were not benefited. One or no anticonvulsant was continued in 80%, and 89% were ambulatory. Outcome was correlated with etiology; patients with seizures caused by migrational disorders were controlled in 51%, whereas those with other seizure etiologies (Rasmussen and congenital vascular) were seizure-free in 71% (p=0.05). 
COMMENT. The Johns Hopkins extensive series of hemispherectomies for intractable seizures demonstrates a beneficial response in 86% of cases, and the outcome is particularly favorable in patients with seizures due to Rasmussen syndrome and vascular disorders. The ideal time to operate remains undetermined. Significant morbidity or mortality occurred in 7%.