Abstracts

Rationale: This retrospective study aimed to compare the identification of the epileptogenic zone (EZ) and postoperative seizure outcome in the patients with MRI-negative (MRI-NL) drug-resistant epilepsy (DRE) using stereoelectroencephalography (SEEG) versus those using subdural grid/strip electrode (SDE) and to evaluate the predictive factors associated with seizure outcome in them.

Methods: Fifty-one patients with MRI-NL DRE underwent the comprehensive noninvasive (phase I) and invasive (phase II) presurgical studies using SDE or SEEG, followed by tailored epilepsy surgery.

Results: The mean age of the patients at epilepsy surgery was 21.3±13.3 years. Of the 51, the patients of SDE- and SEEG-group were 34 (66.7%) and 17 (33.3%) respectively. The results of phase I studies were not significantly different between two groups. The EZ of insular or cingulate gyrus was revealed exclusively in SEEG-group compared to SDE-group (52.9% vs. 0.0%, p < 0.001). Laser ablation was utilized in SEEG-group more often than that in SDE-group (52.9% vs. 2.9%, p < 0.001) as a treatment. The SEEG-group showed a significantly better seizure-free outcome than the SDE-group (64.7% vs. 35.3%, p=0.047) at the last follow-up. In the multivariate regression, detection of the EZ of insular or cingulate (p=0.012, OR=17.23) and the ipsilateral hypometabolism on the positron emission tomography (p=0.032, OR=5.53) were independent predictive factors associated with postoperative seizure-free outcome in the patients with MRI-NL DRE.

Conclusions: Postoperative seizure outcomes, even in patients with MRI-NL DRE, can be improved by identifying the hidden EZ of the deep cortex, including insular or cingulate, through comprehensive invasive EEG monitoring using SEEG.

Funding: Please list any funding that was received in support of this abstract.: None.