Abstracts

This study was undertaken to examine the accuracy of questionnaire information on the occurrence of epilepsy, fever seizures, staring spells and other seizures in first degree relatives of twins, who did not report any history of seizures in themselves. Mailed questionnaires were used to query participants of the Norwegian Twin Panel about history of seizures in the twins and their first degree relatives. Families where one or more first degree relatives was reported to have had any of these conditions without any such diagnoses in the twins themselves were studied. These relatives were first contacted through the reporting twin, as name and contact information of relatives were not requested. Seizures and epilepsy syndromes were classified in the relatives, based upon an evaluation of medical history information and detailed family and clinical interviews. A total of 1266 first degree relatives, included in 1040 twin families, were reported by unaffected twins to be affected by epileptic seizures. Of the 1106 twins who reported affected family members, 887 (80.2%) were found to have provided correct information on the affected status of their relatives, while reports from 219 twins could not be verified. In three of these latter cases, the reported case of epilepsy was actually a febrile seizure, while four reports of febrile seizures were found to be epilepsy. Reports provided by 212 twins were mistakes.
Of the 1266 relatives reported on by the twins, 109 were deceased and could not be examined, 59 suffered from other medical conditions and for 152 of the relatives, the twins denied having reported that their relative had had seizures. Of the remaining 946 relatives, 578 from 572 families were willing to participate in a research study (61.1%), while 368 refused such participation. An additional 291 family members with a verified history of epileptic seizures were identified in the families of those relatives who agreed to this participation. The identification of large families with several affected family members are of great importance for studies on the molecular genetic basis of epilepsy. This study show that surrogate information provided by twins about history of epileptic seizures in their first degree relatives is fairly accurate and demonstrates that questionnaire surveys can be a valuable tool in obtaining seizure history information about first degree relatives of the informant, even when the informants did not suffer from this disorder. Further, more than 60% of the relatives in whom a history of epilepsy was confirmed were willing to participate in further studies, despite the fact that the information about them were provided by a surrogate and contact was made through an unaffected family member. (Supported by a grant from NIH NINDS (NS31564).)