Risk factors for generalized tonic-clonic seizures: a population-based case-control study in Rochester, Minnesota.

This investigation is, to our knowledge, the first population-based case-control study of prenatal, perinatal, and postnatal risk factors for generalized tonic-clonic seizures (GTCS). The clinical diagnosis of GTCS was confirmed through the independent review of the complete medical history of potential cases by three neurologists. All subjects with onset of GTCS before age 30 who were residents of Rochester, Minnesota at time of diagnosis between 1935 and 1979, and who were born in this community, were included (N = 53). Two controls were matched to each patient, and for both patients and controls, the unique records-linkage system for residents of Rochester was used to obtain information about possible risk factors. A history of convulsions in the mother, febrile seizures, and head trauma were significantly more common in cases than in controls. However, factors previously suggested such as: advanced age of the mother, previous miscarriages, gestational toxemia or eclampsia, bleeding during the index pregnancy, low birth weight, asphyxia, or postmaturity were not confirmed. Based on the present and previous studies, we suggest that different types of seizures have different risk factors and should, therefore, be investigated separately.