Patterns of arousal in comatose patients.

The EEG changes, with associated cardiorespiratory phenomena and, where possible, postmortem findings, are described in six patients in coma, with some reference to other similar cases. Spontaneously occurring periodic changes were observed at varying intervals between 20 s and 4 min but most commonly at 1/2-2 min. These involved simultaneous cardiorespiratory, EEG, and somatic motor phenomena related to changes in the level of arousal. It is suggested that a physiological periodicity of the arousal mechanisms exists which may be of importance in the understanding of the pathophysiology of comatose states.