Abstracts

Rationale: Approximately 20% of pediatric epilepsy will prove refractory to medical therapy, and in select patients, resective surgery offers the highest chance of seizure freedom. However, seizure outcomes can be disappointing with 30-50% of children not achieving seizure freedom. For these, subsequent resective surgery may be an option. This study investigates the preoperative work-up and postoperative seizure outcomes for each surgery in pediatric patients who have undergone multiple resections, with the goal of identifying factors that may guide the care of future patients to result in a single, successful resective operation, as well as assessing chance of seizure freedom after subsequent resection.Methods: After obtaining appropriate IRB approval, the epilepsy surgery database was reviewed to identify all pediatric patients (18 years and younger at most recent surgery) having undergone two or more resective surgeries for refractory epilepsy, with at least one occurring at Mayo Clinic between 2005 and 2012. Resective surgery was defined as focal resection of seizure onset zone, or hemispherectomy (functional or anatomic) for hemispheric seizure onset, as defined by imaging and EEG studies. Exclusion criteria consisted of tumor or vascular malformation on pathology; and corpus callosotomy as one of the surgical procedures, as this was considered a palliative surgery. We assessed the percentage of patients undergoing specific testing at first and subsequent preoperative workups, and the percentage that had invasive EEG monitoring at the time of first and subsequent workups. Results: Eleven patients were identified who met inclusion criteria. Etiology included malformations of cortical development in 7/11 (64%); and perinatal MCA infarct, post-viral encephalitis, Rasmussen s encephalitis, and unknown etiology in 1 each. There was no variability in preoperative work-up for initial and subsequent surgeries in 5/11 patients. Intracranial EEG was done as part of the work-up in 6/11 initial surgeries, and 8/11 subsequent surgeries. Three patients (27%) had nonlesional MRIs, all of whom had malformations of cortical development on pathology. Final outcome was Engel class 1 in 6 patients (55%), Engel 2 in 2 (18%), Engel 3 in 1 (9%), and Engel 4 in 2 (18%), with a mean follow-up of 29 months (median 17 months, interquartile range 4-57 months).Conclusions: Based on our short case series, we conclude that epilepsy secondary to cortical dysplasia, especially if not seen clearly on MRI, can be difficult to cure surgically. Acute or chronic iEEG should be done on initial work-up in cases where imaging or EEG studies are ambiguous or conflicting. As large of a resection as can be safely accomplished in the case of a focal cortical resection should be done, particularly in cases with palliative goals. Finally, we conclude that repeat resection should be considered if a first resection fails to achieve adequate seizure control, as 55% in our cohort achieved an excellent outcome after repeat surgery.