Genetic EEG traits in the pathogenesis of the epilepsies

Twin and family studies have proven that the normal EEG and its variants ape genetically determined. Lf the various genetic types of normal EEG reflect different structural and biochemical properties of the brain with different levels of excitability, relationships between these EEG characteristics and seizure liability have to be expected. Even today, though, Little is known about these relationships. The monomorphic alpha EEG favors the generation of generalized spikes and waves and increases the expression of the photoparoxysmal response. The flat EEG, by contrast, is not associated with a genetic seizure liability but appears to have an ''ictophobic'' character. The genetics of several EEG patterns related to epilepsy, i.e., generalized spikes and waves, photoparoxysmal response, theta rhythms, and focal sharp waves, have been studied in detail. The underlying functional anomalies are able to increase the susceptibility to seizures. However, the lowering of the threshold reaches critical levels only if different genetic anomalies coincide in the individual case. The resulting additive effects appear to play a particularly important role in the pathogenesis of the epilepsies. Genetic studies of epilepsies should not be based on determining the incidence of cerebral seizures in relatives alone, but must also include the genetic susceptibility factors that are expressed in the EEG. (C) 1997 by Elsevier Science Inc.