Abstracts

Rationale: Pediatric focal epilepsies often involve more extratemporal regions than adult epilepsies. This study aims to investigate the population of oligodendroglia-like cells (OLCs) in the pediatric focal epilepsy patients requiring surgery. We hypothesize that OLCs are one of the factors that extend the pediatric epileptic network in intractable epilepsy. Methods: Thirty (18 female) children (1.8-16.9 years old with a mean of 9.7 years), who underwent resective surgery for the intractable epilepsy from 2010 to 2012 were retrospectively studied. Eight autopsy cases without neurological disease served as controls. The neuropathology examination utilized the H&E/LFB stain and immunohistochemical staining for NeuN, GFAP and Olig2 as a marker of OLCs. OLCs were counted in three sites: a) gray matter, b) junction of gray/white matter, and c) white matter. We also examined the correlation between OLC populations among the three sites and the clinical features. Results: Seizure types consisted of partial seizures in 17 children epileptic spasms in 9 children, and partial seizure with secondary generalization in 4 children. Fifteen (50%) children underwent multiple lobe resections, consisting of both lateral temporal and extratemporal lobe resections in 12 children and extratemporal lobe resections in 3 children. The other 15 (50%) children underwent single lobe resection including 3 (10%) children with temporal lobectomy sparing hippocampus. Pathological diagnosis of epilepsy patients was as follows; 14 (47 %) children = focal cortical dysplasia (Type I, 4; II, 9; III, 1); 6 (20%) = oligodendrogliosis; 6 (20%) = astrocytic gliosis; 2 (7%) = hyaline protoplasmic astrocytopathy and 2 (7%) = tuberous sclerosis complex. OLC populations at all three sites in epilepsy group were significantly higher than those of control group (p <0.001). In the epilepsy group, there was a significant difference among OLC populations at gray matter, junction of gray and white matter, and white matter (p <0.001). OLC populations significantly increased from gray matter and junction of gray/white matter to white matter. In the control group, there was no difference among OLC populations at three sites. There was no significant difference in the numbers of OLCs between focal cortical dysplasia types I and II. Numbers of resected electrodes significantly correlated with OLC population at junction and white matter. White matter OLC population of multiple lobe resections in 15 children were significantly higher than that of single lobe resection in 15 children. Conclusions: Increased OLC population may play a role of recruiting the extensive epileptogenic zones in pediatric intractable focal epilepsy.