Long-term neuropsychological outcome was studied in 71 children who underwent hemispherectomy for severe and intractable seizures at the Johns Hopkins Hospital between 1968 and 1997. The cause of the seizures was cortical dysplasia in 27, Rasmussen syndrome in 37, and vascular malformation or stroke in 7. Mean age at surgery was 7.2 years. Seizures were completely controlled in 65% at average follow-up of 5.4 years, and 49% had discontinued medications. Mean IQ correlated with seizure etiology: 70s for Rasmussen and vascular patients, and 30s for cortical dysplasia patients. No significant change in cognitive measures occurred between surgery and follow-up. 
COMMENT. Cognitive outcome in children with hemispherectomy for seizures is correlated with seizure etiology, patients with cortical dysplasia having lowest scores in intelligence and language while visual motor skills are relatively spared.