INTRAOPERATIVE ELECTROCORTICOGRAPHY DURING TUMOR RESECTION - IMPACT ON SEIZURE OUTCOME IN PATIENTS WITH GANGLIOGLIOMAS

Gangliogliomas are indolent neoplasms that are often associated with l ong-standing intractable seizures. The seizure-free outcome following ganglioglioma resection alone (or ''lesionectomy'') has been generally favorable. ranging in most series from 50% to 65%. Thus, the value of resection of epileptogenic cortex in addition to tumor with regard to seizure outcome has been the subject of controversy. The authors desc ribe a series of 12 patients with frontal or temporal lobe ganglioglio mas associated with long-standing intractable seizures. In these patie nts, intraoperative electrocorticography was used to guide the resecti on of epileptogenic cortex along with tumor. Functional brain mapping, interictal and ictal monitoring of seizures, as well as thorough neur opsychological assessments were performed prior to resection in all ca ses. Outcome with regard to seizures' tumor recurrence, and neurologic al deficits was assessed with a mean follow-up period of 3.1 years. Th ere was universal freedom from seizures postoperatively in 11 patients in whom complete or near-complete resection of epileptogenic cortex w as achieved. In one patient in whom complete tumor resection and subto tal removal of epileptogenic cortex was achieved, a 95% reduction in s eizure frequency was identified. No tumor recurrence or neurological d eficits were observed. In a subset of four patients, neuropsychologica l and cognitive function were evaluated pre- and postoperatively. In t hese four, a clear trend toward improvement was noted in most function s. Thus, resection of epileptogenic cortex along with tumor may improv e seizure outcome in selected patients with tumor-associated epilepsy without engendering identifiable neurological or cognitive deficits at tributable to the incremental resection.