Abstracts

Rationale: Surgical is considered the best option for drug-resistant epilepsy when the seizure focus is well localized. However, non-invasive tests may not provide adequate localization in some patients leading to rejection of surgical candidacy. Many literatures have shown the effectiveness of bilateral intracranial EEG (iEEG) survey to discover a seizure focus in this situation. According to our experiences with extensive bilateral iEEG monitoring (n=24), there was about 40% of cases that bilateral iEEG could not reveal a seizure focus. However, these patients warrant a further evaluation because of the catastrophic nature of their epilepsy. A novel multistage procedure utilizing bilateral iEEG and complete corpus callosotomy (CC) during a single hospital stay was proposed to help these patients. When seizure focus could not be localized through bilateral iEEG, CC was performed to look for a primary seizure focus on ensuing iEEG.Methods: We retrospectively reviewed 24 patients who received bilateral iEEG monitoring because of unlocalizing seizure focus from presurgical evaluation at Florida Hospital for Children from Sep 2011 till May 2013. The evaluation comprised scalp video-EEG and various neuroimaging tests including 3T-MRI, MEG, FDG-PET, and SPECT. A bilateral craniotomy with broad reverse question mark incision was performed to provide wide access for extensive subdural electrode placement. Among 24 patients, 14 underwent resective surgery following the initial bilateral iEEG. Three cases showed clear independent multifocal seizure onsets and received CC as the final treatment. The remaining 7 cases with diffuse bilateral iEEG underwent the proposed multistage procedure, CC through a vertex craniotomy followed by additional bilateral iEEG. Results: In all 7 patients (age 4 mo 15 yr, M 3 F 4), their pre-CC iEEG could not provide adequate lateralization or localization. The post-CC iEEG findings altered significantly in 5 cases, which led to resection of epiletogenic foci (n=3) or functional hemispherectomy (n=2). Multiple subpial transection was performed bilaterally in one case with multifocal seizure onset on post-CC iEEG. One patient stopped having seizures after the CC and post-CC iEEG showed near complete disappearance of interictal spikes. All 5 patients became seizure free (mean follow-up duration 10.2 mos; 1 -16 mo). None developed unexpected complication from the multi-stage procedure. One patient (F/15) developed acute disconnection syndrome from complete CC, but completely recovered within a month. Conclusions: Our experiences with these 7 patients demonstrated that multistage surgical procedure can be carried out safely and effectively for localization of primary seizure focus in otherwise unlocalizing intractable epilepsy patients. The proposed procedure may broaden the availability of epilepsy surgery and improve overall surgical outcomes. Long-term follow-up in larger number of patients is needed for the validation of this approach.