Periodic activity in electroencephalography.

We report ana analysis of 12 cases in which periodic activity was observed in more than one EEG recording in patients with subacute sclerosing panencephalitis (4 cases), encephalitis of unknown etiology (1 case) and vascular disease (7 cases). In the patients with infective disease periodic high voltage potentials were elicited from all over the brain and the background rhythm was markedly impaired. In the patients with vascular disease the bursts were localized, reversible and sometimes recurrent. The impression gained is that a periodic EEG pattern denotes a pathological modification of behavior of the cerebral cortex rather than any particular disease.