Abstracts

Rationale: Epileptic spasms (ES) manifested subtle clinical symptoms, however some of children with ES become refractory to anti-epileptic medications. They often required multilobar resections to stop ES. We compared the occurrence rate (OR) of high frequency oscillation (HFO) and modulation index (MI) between children with ES (ES+ group) and without ES (ES- group), who required multilobar resections. In ES+ group, we hypothesized that 1) pathological HFOs are more widely distributed and 2) there are more severity of the epileptogenicity than ES- group. Methods: We retrospectively reviewed 24 children with drug-resistant multilobar onset epilepsy underwent IVEEG recordings prior to surgical resection. We assessed 10 ES+ children and 14 ES- children. We selected 5 epochs of 5 minutes interictal EEG during slow wave sleep. We measured the OR of HFO at each electrode and determined the electrodes with High-OR(HFO) by clustering analysis. We measured MI between two HFOs (Ripple/Fast ripple [FR]) amplitude and five phases of slow waves (0.5-1Hz; 1-2Hz; 2-3Hz; 3-4Hz; 4-8Hz). Results: The age of seizure onset in ES+ group (mean 2.7 years) was significantly younger than that of ES- group (5.4 years) (p=0.04). Nine (90%) ES+ children and 5 (36%) ES- children underwent subtotal hemispherectomy consisting of front-temporo-parietal resection skipping the motor area. The remaining 10 children underwent multilobar resections (≥ two lobes). ILAE class Ia outcome was achieved in 18(75%) consisting of 7(70%) ES+ children and 11(79%) ES- children. OR(Ripple&FR) in the resection area and the number of resected High-OR(Ripple&FR) electrodes were significantly higher in the good seizure outcome group than those in the poor seizure outcome group. The number of resected electrodes of ES+ group were significantly higher than those of ES- group (p(FR) in the resection area and the number of resected High-OR(FR) electrodes were significantly higher than those of ES- group.MI(Ripple/FR&3-4Hz) in resection area were highest among the 5 phases of slow wave. MI(Ripple/FR&3-4Hz) in the resection area were significantly higher in the good seizure outcome group than those in the poor seizure outcome group. In ES+ group, MI(FR&3-4Hz) in the resection area were significantly higher than those of ES- group. There were significant correlation coefficients between MI(Ripple&3-4Hz) and MI(FR&3-4Hz) in both ES+ and ES- groups. The slope of regression line was no overlapping of 95% confidence interval between ES+ and ES- groups. Conclusions: OR(Ripple&FR) and MI(Ripple/FR&3-4Hz) could be the biomarker of epileptogenic zone. Higher-OR(FR) and Higher-MI(FR&3-4Hz) in ES+ group compared to ES- group are a signature of the severity of epileptogenicity. In ES+ group, the more extensive zone with resected High-OR(FR) electrodes comparison to ES- group indicated the widespread epileptogenicity. We demonstrated that the raging ocean of epileptogenic HFO in ES+ children who achieved seizure freedom by the extensive resection. Funding: No