Abstracts

Rationale: Pediatric epilepsies often involve more extratemporal regions than adult epilepsies. Multiple lobe resections are often required in children with intractable epilepsy. Oligodendroglia-like cells (OLC) have been observed in surgical specimens from children with intractable focal epilepsy. We hypothesize an increased population of subcortical OLC requiring multiple lobe resections because of wiring the extensive epileptogenic zones in children with intractable epilepsy.Methods: We examined the surgical specimens from 30 children (mean age; 9.7 years old). Immunohistochemical assay of OLC were performed using Olig2, which is a marker of OLC. The OLC population in 3 sites [gray matter, junction of gray/white matter (G/W), white matter] were counted. The OLC results were compared with the seizure types, scalp and intracranial EEG, MRI, surgical resection area, histopathological diagnosis, and seizure outcome.Results: Seizure types consisted of partial seizures in 17 children, epileptic spasms (ES) in 9, and partial seizure with secondary generalization in 4. The other 15(50%) children underwent single lobe resection. Pathological diagnosis consisted of; 14(47 %) focal cortical dysplasia (Type I, 4; II, 9; III, 1); 6(20%) oligodendrogliosis; 6(20%) astrocytic gliosis; 2(7%) hyaline protoplasmic astrocytopathy; 2(7%) tuberous sclerosis complex. 9 children with ES showed significantly increased OLC population at junction of G/W (p=0.021) and white matter (p=0.025) compared to 21 with other type of seizures. 8(89%) of 9 children with ES underwent multiple lobe resection, compared with 7 (33%) of 21 children with partial seizures requiring multiple lobe resection (p=0.0142). 11 children with interictally non-focal epileptic discharge on scalp EEG showed significantly increased OLC population at white matter compared to 19(63%) with only focal epileptic discharge(p=0.01). 9 children with ictally non-focal epileptic discharge on scalp EEG significantly increased OLC population at junction of G/W (p=0.04) and white matter(p=0.042) compared to 21 with focal epileptic discharges. The OLC population at white matter in 15 children who underwent multiple lobe resections, were significantly higher than that in 15 children who underwent single lobe resection(p=0.028). The number of resected electrodes significantly correlated with OLC population at white matter (correlation coefficient 0.581, p=0.001) and junction of G/W (correlation coefficient, 0.426, p=0.027). 25(83%) children became seizure free after 12(40%) multiple lobe resection and 13(43%) single lobe resection.Conclusions: The intractable epilepsy children may require the multiple lobe resection, because the epileptogenic zone extended to the extratemporal lobes with both interictally and ictally non-focal EEG. When children presented with ES rather than partial seizure, they highly required multiple lobe resections. The increased subcortical OLC can cause of wiring the extensive epileptic network in children to require the multiple lobe resections.