Periodicity and Hypsarrhythmia in the EEG

Abstract

Introduction In 1956 and 1958 Lesse, Hoefer, and Austin^1,2 reported on clinical and electroencephalographic (EEG) findings in 11 patients suffering from a variety of diffuse encephalopathies of different etiologies and clinical outcome, but with a common EEG abnormality, namely, periodic synchronous bursts of irregular slow and spike-and-wave activity, mainly of high amplitude and with depression of activity in the interval. It was our impression that the EEG pattern was related to a profound cerebral, chiefly cortical, disturbance. The clinical features of this disturbance are: organic mental changes, myoclonic and generalized convulsions, rigidity, and a choreo-athetoid form of dyskinesia. Earlier authors^3,4 had considered the EEG pattern to be specific for subacute sclerosing leukoencephalitis of the Dawson⁵ and van Bogaert⁶ varieties. Only one of our own original cases fell into this category, and we concluded that the clinical picture was indicative of a state of physiological impairment with