EPILEPSIES IN TWINS - GENETICS OF THE MAJOR EPILEPSY SYNDROMES

We studied twins to examine the genetics of epilepsy syndromes. We asc ertained 358 twin pairs in whom one or both reported seizures. After e valuation, 253 of 358 (71%) had seizure disorders and 105 pairs were f alse positives. Among the monozygous (MZ) pairs, more were concordant for seizures (48 of 108; casewise concordance = 0.62 +/- 0.05) than am ong the dizygous (DZ) pairs (14 of 145; casewise concordance = 0.18 +/ - 0.04). In 94% of concordant MZ pairs, and 71% of concordant DZ pairs , both twins had the same major epilepsy syndrome. When analyzed accor ding to major epilepsy syndrome, the casewise concordances for general ized epilepsies (MZ = 0.82; DZ = 0.26), both idiopathic (MZ = 0.76; DZ = 0.33) and symptomatic (MZ = 0.83; DZ = 0), were greater than those for partial epilepsies (MZ = 0.36; DZ = 0.05), with intermediate value s seen for febrile seizures (MZ = 0.58; DZ = 0.14) and unclassified ep ilepsies (MZ = 0.53; DZ = 0.18). We conclude that genetic factors are particularly important in the generalized epilepsies but also play a r ole in the partial epilepsies. The high frequency of concordant MZ pai rs with the same major syndrome strongly suggests there are syndrome-s pecific genetic determinants rather than a broad genetic predispositio n to seizures.