Hemispherotomy and functional hemispherectomy: indications and outcome

Peri-insular hemispherotomy is a disconnective procedure that enables functional isolation of single or multiple epileptogenic regions largely involving one hemisphere. This report is based on a consecutive series of 13 pediatric patients affected by refractory hemispheric epilepsy studied and operated on at the Neurological Institute "C. Besta" of Milan. In all patients seizures were focal with polymorphic features and daily frequency. Preoperative electro-clinical and MRI data were suggestive of Rasmussen's encephalitis in 6 cases, hemimegalencephaly in 2, hemispheric cortical malformation in 3, perinatal stroke in 2 cases. Mean age at surgery was 7.3 years. The postoperative course was good for all patients. Mean follow-up period was 4.5 years (range 2-7 years). After hemispherotomy, 8 patients were Engel Class I and five continued to have seizures and were classified as Engel Class II (1 case) III (3 cases) or IV (1 case). The outcome results varied according to the etiology; the best results were achieved in patients with Rasmussen encephalitis and perinatal vascular strokes with 75% classified in Engel Class I. Three patients underwent a second surgery because of persistent seizures and evidence of incomplete disconnection; two out of three patients had hemimegalencephaly, and did not improve; the third patient with perinatal stroke resulted seizure free. We conclude that hemispherotomy can be performed successfully to treat medically intractable hemispheric epilepsy, providing remarkable results in terms of seizure outcome and quality of life.