Occipital 3-4/s-rhythms in childhood EEG.
Report of follow-up studies in 65 children with occipital slow rhythms in the EEG (287 records). Two types of occipital rhythms can be differentiated: Paroxysmal bursts of 3--4/s-rhythms with high amplitude (I) accentuated by closing eyes and continuous usually regular occipital 3--4/s-rhythms (II). Type I is identical with the sinusoidal occipital 3/s-rhythms, which are observed especially frequently in childhood epilepsies. It could be demonstrated by follow-up studies, that the phenomenon usually disappears at latest during puberty. --The second type may also disappear during puberty or may even persist until the adult age. This persisting type is identical with what is quoted as "Grundrhythmusvariante" in the German literature. The continuous occipital rhythms could be demonstrated at earliest at age 3. The rhythms change their shape, amplitude, frequency and localisation during growth: In children prior to age 10 the rhythms show more often occipital accentuation in monopolar leads (against ear as reference); the amplitudes are higher on average; the frequency is often less than 4/s, and alpha groups preceding the rhythms after closing the eyes are less pronounced than in older children. Subharmonic waves are frequent. In the same manner as in adults a mostly right sided lateralisation can be seen. Genetic factors may be involved in the development of the occipital rhythms, although a simple mendelian transmission could not be confirmed. The EEG phenomenon is correlated with symptoms of psychic and vegetative lability. There is no correlation to epilepsy. The high incidence of anamnestic risk factors suggests that exogenous factors are at least contributing to the development of the rhythms. The continuous occipital 3--4/s-rhythms must be understood as the symptom of a disturbed development of central pacemaker systems. It can lead to persisting abnormalities or only occur transitorily in certain stages of the brain maturation.