Digital computer-analyzed resting and sleep EEGs (sleep prints) after hemispherectomy in man

Abstract

Resting and sleep EEGs of a patient with a left hemispherectomy were studied using digital computer period analysis and sleep print methods. It was observed that certain EEG potentials recorded in the operated side are not merely a smaller version of the activity originating in the unoperated side. The significantly more frequent occurrence of certain bioelectrical potentials in the operated side, and particularly the fluctuation of the differences in these potentials between the two sides during different phases of sleep, rules out the hypothesis that this activity is exclusively spread from the unoperated hemisphere and suggests the existence of indigenous bioelectrical phenomena in the operated side. Generally, a greater amount of slow potentials, alpha waves and over 40 c/sec superimposed fast activity was seen in the operated than in the unoperated side, indicating that subcortical structures are predominantly responsible for these activities. In contrast, 16–26 c/sec waves, K complexes, parietal humps, vertex sharp waves and spindle activity occurred mainly in the unoperated side, suggesting that these activities are dependent on an intact cortex or an intact thalamocortical functional system or both. The all-night sleep profiles of both hemispheres exhibited almost identical patterns, although the operated side revealed more slow wave spindle sleep.