Abstracts

Rationale: The aim of our study was to assess the classification of new onset epilepsy in a population-based group of children using the new ILAE Commission on Classification and Terminology 2005-2009 Report. We also assessed the frequency of specific syndromes and distinctive constellations in this population. We examined the level of agreement amongst pediatric epileptologists utilizing the new classification system.Methods: Using the Rochester Epidemiology Project, we identified all children, ages 1 month through 17 years, who resided in Olmsted County, MN and were diagnosed with new onset epilepsy between 1980 and 2009. Epilepsy was classified by mode of onset, etiology, and (if applicable) syndrome and distinctive constellation. All cases were classified by two pediatric epileptologists blinded to the other s classification. Classifications were compared and Kappa scores were calculated to measure agreement.Results: A total of 468 children were identified. The majority (67.9%) had seizures of focal onset. The remaining children had generalized (24.1%), generalized and focal (0.9%), spasms (3%), and unknown (4.1%) modes of onset. Almost half (49.6%) of childhood-onset seizures were of unknown etiology; the vast majority of these (192/232, 82.8%) were also not classifiable into a specific epilepsy syndrome. The remaining seizures were secondary to known/presumed genetic (23.3%), structural/metabolic (26.7%), or both genetic and structural (0.4%) etiologies. Over one fourth (28.8%) of children with new onset epilepsy could be classified as having a specific epilepsy syndrome (see Table 1). However, only 2.4% could be classified as having a distinctive constellation (mesial temporal sclerosis 1.9%, hypothalamic hamartoma 0.2%, Rasmussen s encephalitis 0.2%). There was excellent agreement (96.6%) between epileptologists utilizing the new ILAE classification system. Disagreements were in the mode of onset in 8 (Kappa 0.964, asymptotic standard error 0.012), etiology in 2 (Kappa 0.993, asymptotic standard error 0.005), and syndrome in 6 cases (Kappa 0.978, asymptotic standard error 0.01).Conclusions: Despite advances in imaging and laboratory testing, the etiology of nearly half of childhood epilepsy remains unknown. No clear syndrome or distinctive constellation can be identified in nearly half of children with new onset epilepsy. Further work is needed to elucidate the underlying etiologies in this group. There was excellent agreement between two pediatric epileptologists using the new ILAE classification system, further supporting its adoption.