Incidence of epileptic syndromes in Rochester, Minnesota: 1980-1984

Abstract

Purpose: To determine the incidence and the distribution of epileptic syndromes in a well-defined population. Methods: By using the records-linkage system of the Rochester Epidemiology Project, we screened all the residents of Rochester, Minnesota, who received a diagnosis of seizures, convulsions, or epilepsy from 1980 through 1984. One hundred fifty-seven residents with incident epilepsy (recurrent unprovoked seizures) were classified by using the International League Against Epilepsy (ILAE) Classification of the Epilepsies and Epileptic Syndromes. Residents with special syndromes were excluded. With a pretested algorithm, patients were classified at three levels of specification: major syndromic groups (e.g., localization-related syndromes), syndromic subgroups (e.g., idiopathic epilepsy with age-related onset), and whenever possible, individual syndromes. Results: All but one patient were classified into major syndromic groups and subgroups. The annual age-adjusted incidence per 100,000 population was 52.3 cases (34.9 for localization-related epilepsies; 7.7 for generalized epilepsies; 9.7 for undetermined epilepsies). Incidence was 0.2 for idiopathic, 17.2 for cryptogenic, 17.5 for symptomatic localization-related epilepsies, 3.7 for idiopathic, 1.7 for symptomatic or cryptogenic (age-related), and 2.3 for symptomatic (non age-related) generalized epilepsies. Conclusions: With the exception of idiopathic epilepsies, the incidence of the major syndromic categories in our study was higher than that provided by previous population- based studies.