Generalized, bilaterally synchronous bursts of slow waves in the EEG.

Forty-two patients who had bursts of spontaneous, bilaterally synchronous slow waves during the waking state in an otherwise normal EEG were compared with 42 age-matched control subjects with normal EEGs. The study group had a significantly higher incidence of diffuse encephalopathy than did the control group. They also had a higher incidence of alterations of consciousness. None of the patients in the study group had focal, deep midline lesions. This study indicates that generalized, bilaterally synchronous slow bursts in the EEG are significant abnormalities that in the majority of cases are associated with a mild to moderate diffuse encephalopathy rather than with a lesion limited to deep midline structures.