Abstracts

Rationale: The SEEG methodology was developed and popularized in France by Tailarach and Bancaud during the 50 s and mostly used in Europe, as the method of choice for invasive mapping in refractory focal epilepsy. Despite a long reported successful record, its application in the United States was not reported up to now. Our aim is to report seizure outcome and predictor factors associated with seizure freedom in patients who underwent resective surgery guided by SEEG implantation.Methods: Between March 2009 to May 2011, 100 consecutive patients with the diagnosis of medically refractory focal epilepsy underwent SEEG implantation in our institution. Data regarding age, gender, history, seizures semiology, EEG, neuropsychological test, PET, SPECT, magnetoencephalography, number and location of implanted electrodes, possible localization of the epileptogenic zone, surgical pathology, complications and seizure outcome after resection were prospectively collected and analyzed. A minimal follow-up of 6 months was used as inclusion criteria. We assessed the statistical correlation between seizure outcome, complications and categorical variables using univariate and multivariate analysis. Significance was set at a p value of 0.05. Results: The mean group age was 32 year-old (54M/46F). Sixty-one patients had normal or extensive bilateral abnormalities on the MRI. Twenty-seven patients had previous resections. Seventy-five patients underwent surgical resection. From this group, 53 patients met the inclusion criteria of minimum post-resection follow-up of 6 months. In this group, the mean follow-up was 11.7 months (range from 6 months to 24 months). Twenty-two patients (41.5%) had unilateral abnormal MRIs and 31 patients (58.5%) had normal MRIs (28 patients) or bilateral abnormalities (3 patients). Resection strategies included temporal lobe resections in 14 patients (26%), extra-temporal resections in 26 patients (49%). Seven patients had normal pathology and 45 patients abnormal pathology. In the group of 53 operated patients with a minimum follow-up period of 6 months, 33 patients (62.3%) became seizure-free. Type of operation, side of resection or MRI findings were not statistically associated with seizure-free outcome. Surgical pathology was the only variable statistically associated with seizure outcome (p=0.005). Normal pathological findings were statistically associated with poor post-resection outcome. The presence of pathological findings, as mild forms of cortical dysplasia (type Ia) or mesial temporal sclerosis were strongly associated with post-operative seizure control. Complication rate was 2%.Conclusions: In this highly complex and challenging group of patients, resective surgery guided by SEEG provided promising results (62% seizure freedom rate) with an acceptable complication rate. Abnormal surgical pathology (mainly cortical dysplasia) was the only variable associated with a favorable outcome. Long-term outcome studies are mandatory to establish the role of the SEEG methodology in the diagnosis and treatment of refractory focal epilepsy.