EEG longitudinal studies in febrile convulsions. Genetic aspects.

It was the purpose of the study to obtain viewpoints on the genetics of febrile convulsions and their relationship to epilepsy by EEG long term follow up. 89 children with febrile convulsions could be followed up to the age of 11 to 13 years (in total 1046 EEG records). The study was concentrated on genetically determined EEG patterns: bilaterally synchronous spikes and waves, photosensitivity and 4-7 cps rhythms. The statistical evaluation was based on standards derived from known strict age dependence of the different patterns. Theta rhythms were found in 54%, spikes and waves of the resting record in 49% and photosensitivity in 42%. In total, genetically determined EEG patterns were found in 81% of the cases which were sufficiently investigated according to given standards. Spikes and waves are strongly age dependent with a maximum at the age of 5-6 years and appear very inconstantly. Theta rhythms and spikes and waves are closely correlated. Spikes and waves are a heterogeneous phenomenon. The type described here must be interpreted as a facultative symptom of the same functional anomaly which forms the basis of 4-7 cps rhythms. The possible pathophysiological basis of the pattern is discussed.--Photosensitivity is interpreted as the symptom of a genetically independent pathogenetic mechanism, which can lead to additive effects by interaction with other genetic abnormalities as well as exogenous factors.--The pathogenesis of febrile convulsions is multifactorial in the strict sense. While the exogenous pathogenetic factors are rather uniform, the genetic predisposition apparently is not. It is based on different genetic anomalies. Each of them is polygenically determined. In the individual case one or different factors can be involved. The genetic predisposition to febrile convulsions is definitely not only polygenic, but of heterogeneous nature. Finally the genetic relationship between febrile convulsions and epilepsy is discussed.