Abstracts

Rationale: In recent years, cases of insular epilepsy have been accumulating in the literature, suggesting that it may be more frequent than previously thought. Because they may resemble temporal, parietal and even frontal lobe seizures, it has been proposed that some prior epilepsy surgery failures in such lobes were in fact the result of non-recognizing the presence of insular seizures. We sought to identify in our institution such cases Methods: From our epilepsy clinic database, we first retrospectively identified all epilepsy surgeries since 2003 which resulted in a poor seizure outcome (Engel III or IV). Their medical charts and the results of investigations following their initial epilepsy surgeries were then reviewed to identify cases with insular seizures, either proven by a subsequent invasive EEG study or suspected by MEG findings Results: Out of 68 epilepsy surgical failures followed at our epilepsy clinic, we identified 7 cases (all male; mean age 32.4) who probably continued to have seizures because of remaining insular seizures as suggested by postoperative MEG findings (n=6) or a subsequent invasive EEG with insular sampling (n=4). In these patients, the initial surgical procedure consisted in an anterior temporal lobectomy for the removal of mesial temporal sclerosis (n=4), a frontal polectomy (n=1), a medial frontal resection (n=1) or a parietal operculectomy (n=1). Average time to post-operative seizure recurrence was 0.56 months. Subsequent epilepsy surgery which involved the removal of the insula suspect of harboring seizures resulted in the following Engel seizure outcome: Ia (n=4), IId (n=1), III (n=1) and SUDEP (n=1) probably from co-existing orbito-frontal seizures Conclusions: Persisting insular seizures can explain some cases epilepsy surgery failures in the frontal, temporal and parietal lobes Funding: NO