Abstracts

Rationale: There has been increasing interest in the role of insula in intractable epilepsy. The insula is increasingly implicated in suboptimal surgical outcomes in frontal, temporal, and parietal epilepsy. With invasive evaluation via stereoelectroencephalography (SEEG), insular exploration has become increasingly possible as epilepsy centers across the US gain experience with this technique. Methods: Our pediatric center has routinely performed invasive epilepsy surgery evaluations using subdural and depth electrodes. However, since adoption of the SEEG technique in fall 2015, five patients underwent SEEG explorations at our hospital in 2015. We report our experience with insular involvement in refractory epilepsy using this methodology. Results: Five patients with "deep" mesial onset epileptogenic zones (felt to be sub-optimally defined by subdural and depth electrodes) underwent SEEG evaluation. One patient did not have any habitual seizures. Another had cingulate and mesial parietal localization. In 3 of 5, the insula (2L: 1R) was implicated in the seizure onset zone. Their clinical data is summarized in Table 1. All patients underwent orthogonal electrode implantation. Figure 1 illustrates such an electrode in Patient 3 using co-registration with FreeSurfer and Curry 6 programs. Resections included but were not limited to the insula in two. There were no post-operative complications. There has been no seizure recurrence since surgery in all three patients. Conclusions: As our cohort shows, the insula may be part of the seizure onset zone in medically refractory epilepsy more frequently than previously appreciated. For example, the insula has been implicated as a reason for the approximately 30% failure rate in mesial temporal lobe epilepsy. Patient 1, with seizures associated not only with MTS but also independently from the insula, is such an example. While a few publications have discussed direct sampling of the insular region with opening of the operculum & placement of subdural electrodes, SEEG is widely felt to a safer and better tolerated procedure. All 3 patients had baseline high anxiety, but all 3 tolerated SEEG evaluations with minimal discomfort and complaints . While our post-operative follow-up is 7-9 months, our patient cohort shows that with SEEG, exploration of previously poorly accessed regions such as the insula is feasible. SEEG based explorations may augment and optimize seizure free outcomes. Funding: None