The risks Of unprovoked seizures in the offspring of parents with generalized versus partial epilepsies among 687 patients born in Rochester, MN between 1922 and 1985 and followed for the occurrence of seizures through 1986 are reported from the Division of Epidemiology and Department of Neurology, Columbia University, New York, the University of Texas Health Sciences Center, Houston, and the Section of Clinical Epidemiology, Mayo Clinic, Rochester, MN. The incidence of recurrent unprovoked seizures in the total group was 3.3% and three times that expected. The incidence was approximately the same in the offspring of parents with either generalized or partial seizures. For parents with absence generalized seizures the incidence of epilepsy among offspring was substantially higher than that for offspring of parents with other types of generalized onset seizures and was three times as high as for partial cases. The early age at onset and idiopathic nature of the epilepsy explained only in part the higher incidence in offspring of absence cases. These offspring had a higher risk not only for absence seizures but for other seizure types as well, suggesting that absence epilepsy is not genetically distinct from other seizure types of epilepsy. For offspring of parents in the largest subset of generalized seizures (primary generalized tonic-clonic convulsions) there was no evidence of higher risk than for offspring of parents with partial seizures. 
COMMENT. These findings contrast with the widely held assumption that partial epilepsies are less likely than generalized epilepsies to be genetic. The dramatically elevated risks in offspring of probands with absence seizures agreed with the findings of Metrakos and Metrakos (1961). However, in the present study, the increased risk in offspring of absence cases was not restricted to absence seizures, but was observed in all seizure types. The authors suggest that the data are more consistent with a common genetic basis for all seizure types, with absence cases having a higher genetic liability than other cases, leading to a higher risk for all seizure types in their relatives. This study did not take into account the etiology of seizures and febrile convulsions were not included.