HEREDITARY CHARACTERISTICS OF FAMILIAL TEMPORAL-CENTRAL FOCAL EPILEPSY

Abstract

Focal "temporal lobe" epilepsy of genetic etiology is apparently transmitted by a single, autosomal dominant gene. The overall penetrance of this trait is low and is highly age-dependent. It approximates 50% between 5 and 15 years of age and then drops again to a low over-all incidence after 20 years of age. The low penetrance is evident from the fact only 12% of the affected individuals develop seizures, and the risk-of-recurrence rate for clinical seizures in this small group of 12 affected families is approximately 1 in 8. Persistence of genetically determined focal "temporal lobe" epilepsy into adult life, usually with refractory psychomotor seizures, occurred in 13% of affected close relatives in time study and should be considered carefully in any patient who is a potential candidate for temporal lobectomy. Evidence for a genetic etiology has been uncovered in only 30% of the 40 families. In the remaining 70% of families an acquired structural lesion is probably etiologic in some cases. The application of these data to any single patient with epilepsy must be carried out with extreme caution because of the non-specific nature of all EEC abnormalities and the variable nature of the associated clinical seizure. Hence, the physician must remember that he is obligated to study each patient with great care before invoking a genetic explanation for a focal electroclinical seizure. The conclusions proposed in this report have resulted from a controlled study of whole families whose brain-wave patterns were sampled both in cross section and longitudinally. The authors still make no presumptions about their ability to identify accurately an hereditary brain-wave disorder without a thorough clinical and laboratory study of the individual case.