Abstracts

Rationale: Little is known about the distribution of epilepsy susceptibility genes and epilepsy syndromes among racial and ethnic groups. Prior studies found racial differences in the prevalence of the photo-paroxysmal response suggesting possible variability in the prevalence of epilepsy syndromes.Methods: We examined epilepsy classification and race/ethnicity in 452 probands from sibling or parent-child pairs with epilepsy enrolled in EPGP, a multi-center collaborative effort to collect detailed phenotypic and genetic data on a large number of epilepsy participants. Subjects were classified as idiopathic generalized epilepsy (IGE), non-lesional localization-related epilepsy (LRE), mixed epilepsy syndrome (both LRE and IGE), and unclassifiable based on consensus review of available clinical, electrophysiology, and neuroimaging data. Race (White, Black, Asian, Native-American, more than one race, other, and unknown) and ethnic (Hispanic and non-Hispanic) category was based on patient self report. In addition, we examined frequency of generalized tonic clonic seizures (GTCS) and non-GTCS in the different racial and ethnic groups. Chi-square test was used to determine differences in the distribution of epilepsy classification among groups.Results: Of the 359 white subjects (79%), 217 (60%) had IGE, 117 (33%) had LRE, 13 (4%) had a mixed syndrome, and 12 (3%) were unclassifiable. Of the 93 non-white subjects (21%), 44 (47%) had IGE, 41 (44%) had LRE, 1 (1%) had a mixed syndrome, and 7 (8%) were unclassifiable. The proportion of white subjects with IGE was significantly higher than non-whites (Chi-square = 9.621, df =3, p = 0.022). Forty-six subjects identified themselves as Hispanic; 21 (46%) had IGE, 19 (41%) had LRE, 2 (4%) had a mixed syndrome, and 4 (9%) were unclassifiable. Of the non-Hispanics, 240 (59%) had IGE, 139 (34%) had LRE, 12 (3%) had a mixed syndrome, and 15 (4%) were unclassifiable. There was no significant difference between ethnic groups (Chi-square = 4.92, df =3, p = 0.18). Both whites and non-whites had similar severity of epilepsy with 69% and 67% experiencing at least one GTCS, respectively. No significant difference was seen between the proportion of whites (23%) and non-whites (31%) who had > 20 lifetime GTCSs. Conclusions: In this study of patients with a presumed genetic contribution to their epilepsy, IGE was more common in whites compared to non-whites suggesting there may be racial differences in the prevalence of epilepsy syndromes. The proportion of white and non-white subjects is similar to the distribution of racial groups in the general US population despite the historical underrepresentation of minorities in tertiary epilepsy centers, and there was no significant difference in epilepsy severity between groups. Further research is needed to examine whether racial differences in the distribution of epilepsy susceptibility genes might be responsible for these findings or whether there is a significant effect of genetic background on epilepsy phenotype.