Idiopathic generalized epilepsies: do sporadic and familial cases differ?

Genetic factors are the only identified cause of idiopathic generalized epilepsies (IGEs), but the majority of cases do not have affected first-degree relatives. Here we investigate whether subjects with sporadic and familial IGE differ in terms of antecedent events and clinical and EEG features. Differences would support the hypothesis of a different etiology for sporadic cases, which has implications for choice of subjects for genetic association studies.

We analyzed 98 patients with IGE, diagnosed on clinical and EEG criteria. All patients and, if possible, one relative were interviewed, with special emphasis on potential antecedent events and family history. Patients with first-degree relatives affected with epileptic seizures were regarded as "familial," and the other patients were regarded as "sporadic."

Of the 98 IGE patients, 32 (33%) patients were familial. The risk for seizures was 13.2% for siblings, and 7.7% for parents. The distribution of the IGE subsyndromes, the presence of antecedent events, and other electroclinical features did not differ between familial and sporadic IGE groups.

No differences were found between familial and sporadic IGE patients. This does not the support the hypothesis that sporadic and familial IGE cases have separate etiologies.