SEIZURE RISK IN OFFSPRING OF INDIVIDUALS WITH A HISTORY OF FEBRILE CONVULSIONS

One-hundred and seventy-nine offspring of 120 probands with a history of febrile convulsions (FC) were studied to determine the risk of seiz ures and possible factors influencing this risk. The conditions for th is study were especially good since all of the probands had undergone clinical and EEG examinations as well as an assessment of family histo ry of seizures during childhood. Hence, for the first time the seizure status of the probands' parents could be included in the calculation of risk in offspring. In sibs the risk was highest if the mother of th e proband had experienced seizures (20% vs 9% in offspring of probands with nonaffected parents). Similarly, offspring of probands with affe cted mothers had a much higher risk (27%) than offspring of probands w ith affected fathers (7%). Our findings point to a maternal prepondera nce in the transmission of FC liability. No relationship was found bet ween the presence of EEG traits of a genetic seizure liability (theta rhythms, spikes and waves, photoparoxysmal response, focal sharp waves ) in probands during childhood and the seizure risk in their offspring . The present data provide no basis for forming an hypothesis regardin g the possible mode of inheritance of FC. This is not surprising since FC - as already shown in the EEG - are not a homogeneous disorder, bu t are caused by a variety of genetic factors occurring in variable con stellations. Possibly, in a subgroup of probands with seizure affected mothers the susceptibility to FC follows a multifactorial polygenic m ode of inheritance. Conclusion The seizure incidence in offspring of i ndividuals with a history of FC was 10% (only FC in 64% of the affecte d offspring). Offspring of females with affected parents were at an in creased risk. Pathological childhood EEG findings of the probands were not related to an increased risk in offspring.