Background: The revival of epilepsy surgery after the introduction of modern presurgical evaluation procedures has led to an increase in hemispherectomy or hemispherotomy procedures. Since a large part of our pediatric series was done using a newer hemispherotomy technique, we focus mainly on the outcomes after a recently developed hemispherotomy technique (transsylvian keyhole).

Methods: Ninety-six pediatric patients (aged 4 months to 18 years, mean 7.3) were operated on between 1990 and 2009; 92 were available with follow-up.

Results: The most frequent diagnosis was porencephaly in 46 % of all patients. Progressive etiologies were present in 20 % and developmental etiologies in 22 %. At last available outcome (LAO), 85 % of the patients were seizure free (ILAE class 1). Year-to-year outcome was rather stable; usually over 80 % were class 1 for up to 13 years (n = 24). Of 92 assessable patients, 71 were treated with the transsylvian keyhole technique, with 89 % being seizure free. The overall shunt rate was 5.3 % for the whole series and 3 % for the keyhole technique subgroup. Mortality was 1 of 96 patients. Excluding patients with hemimegalencephaly (HME), patients with the shortest duration of epilepsy and the lowest age at seizure onset had the highest rates of seizure freedom. The etiology does influence outcome, with HME patients having the poorest seizure outcome and patients with Sturge-Weber syndrome and porencephaly having excellent seizure control.

Conclusion: Hemispherotomies/functional hemispherectomies are very effective and safe procedures for treating drug-resistant epilepsy with extensive unihemispheric pathology. Etiology and surgery type clearly influence seizure outcome.