[Left-sided lateralisation and localisation of EEG foci in relation to age and diagnosis (author's transl)].

The retrospective evaluation of seven non-selective random tests of a total of 2543 continuously registered EEG foci shows the following results: 1. EEG foci on the left side: 1532 = 63.6%; foci on the right side: 875 = 36.4%. 2. Left preponderance in all decennia, significant from the second decennium onwards in nearly constant measurement. 3. Of all foci, 43.6% were exclusively located in temporal regions (71% on the left, 29% on the right). The foci of the occipital region decreased from 60% to 20% between the first decennium and involution, the foci of the temporal region increased from 26% to 54%. 4. Left preponderance occurred in all kinds of EEG foci, among the delta-foci only because of their accumulation in the temporal region. 5. In all diagnoses, the left side was more frequently affected, most distinctly among vascular disturbances, least distinctly among intracranial space-occupying lesions. 6. Six of seven EEG examiners showed significant left preponderance. The extent of left preponderance and the frequency of reductions of alpha waves, of focal dysrhythmias, and of theta wave foci were dependent on the examiner. 7. The authors discuss the connection between the general left preponderance of EEG foci, which is modified by but not basically dependent on sex, age, and diagnosis, and the greater possibility of disturbing the function of the hemisphere dominating speech development.