Abstracts

To study the occurrence of specific epilepsy syndromes in families with more than two affected individuals. Participants in the Norwegian Twin Panel and the Mid-Atlantic Twin Registry were screened for a history of seizures among themselves and their family members by questionnaire. Based upon an evaluation of medical history information and detailed clinical and family interviews, seizures and epilepsy syndromes were classified in all individuals reporting a positive seizure history using the ILAE classification system. A history of epilepsy was confirmed in two or more members of 587 families. It was possible to classify the epilepsy syndrome in two or more family members in 445 families with 227 being concordant and 218 discordant for syndrome type. Among families concordant for localization-related epilepsies, four had idiopathic epilepsy, 14 symptomatic epilepsy and another 14 families cryptogenic epilepsy. We also identified 173 families who were concordant for special situation-related syndromes and 19 families for generalized idiopathic epilepsy. One family had undetermined epilepsy with both generalized and focal features, while three families had undetermined epilepsy without unequivocal generalized or focal features. After simplifying syndrome types in discordant families into four categories (generalized, localization-related, undetermined and special syndromes), we found that four families had a combination of all categories, 30 families a combination of three categories and 173 a combination of two categories. In 11 families, members had different forms of localization-related epilepsy. Both generalized and localization-related epilepsies were found in separate members of 42 families. The importance of the contribution of genetic factors to risk for epilepsy has been well documented in twin and family studies. Our finding that among multiplex families, where it was possible to determine the epilepsy syndrome type of affected family members, approximately half were concordant and half were discordant for syndrome type provides further support for the existence of two classes of seizure susceptibility genes; those that are syndrome specific and those that are not. Of special interest are the families in which both generalized and localization-related epilepsies occurred. This large collection of families with verified epilepsy provides an important resource for identifying both specific epilepsy genes and more general seizure susceptibility genes (Supported by NIH NINDS grant (NS-31564))