Functional neurosurgery for epilepsy.

Introduced at the end of the last century, epilepsy surgery is indicated in patients with intractable partial seizures and based on the resection of t he epileptogenic cerebral tissue from which ictal discharges originate. Pal liative procedures include seizure spread pathways interruption (callosotom y, multiple subpial transections) and chronic stimulation of the vagus nerv e. Complete preoperative investigations including seizure observation, clin ical tests, video-EEG, MRI and functional MRI, and PET-scan are performed i n order to identify the epileptogenic zone. In difficult cases, invasive se izure monitoring through depth electrode implantation (SEEG) is performed. Resections for temporal lobe seizures are associated with favorable outcome : 60 to 90% of patients will be seizure-free after surgery. A less favorab le outcome is observed after extra-temporal resections : 40 to 60% seizure- free patients. A better outcome is observed after surgery for epilepsy asso ciated with an image-defined lesion, most often a tumor, rather than for cr yptogenic epilepsy. Tumors associated with chronic partial epilepsy are ind olent, most of them are dysembryoplastic neuroepithelial tumors (DNET). Out come after palliative procedures are more variable, depending on the etiolo gy of epilepsy. (C) 2001 Editions scientifiques et medicales Elsevier SAS.