Predicting Seizure Freedom After Two or More Chronic Invasive Evaluations in Patients with Intractable Epilepsy

OBJECTIVE: In patients with intractable epilepsy, failure to localize and/or resect the epileptic focus after invasive monitoring is multifactorial. Rarely do these patients return for a second invasive evaluation, and their outcome is not clearly characterized. This study aims to determine the seizure outcome after a second invasive electroencephalographic (EEG) evaluation, and its possible predictors. METHODS: We retrospectively reviewed 30 patients who underwent two or more invasive evaluations at Cleveland Clinic between 1980 and 2007. Clinical, surgical, imaging, and pathology information was analyzed using a multivariate regression model. A favorable outcome was defined as complete seizure freedom, allowing for auras and seizures restricted to the first postoperative week. RESULTS: Ten patients (33%) became seizure free after the second operation (mean follow-up duration 3.13 years [range 6 months-17 years]). Seizure freedom was more likely in patients reporting fewer seizures per month preoperatively (mean 19 seizures/mo), and in those with a predominantly regional/lateralized scalp EEG ictal pattern (32% seizure free), as opposed to those with higher seizure frequency (mean 70 seizures/month; P = 0.02) or diffuse ictal EEGs (0% seizure free; P = 0.04). There was a significant association between acute postoperative seizures and failure of repeat surgery (P = 0.0083). In 17 of 30 patients, at least one complication was reported (57%) after the second invasive evaluation compared with a complication rate of 23% after the first invasive evaluation. CONCLUSIONS: A second invasive evaluation may lead to seizure freedom in one-third of patients. However, this must be weighed against the increased complication rate with reoperation.