Periodic complexes, absence-like status and suppression-burst pattern in coma following cardiorespiratory arrest

A 75-year-old man suffered a cardiac arrest and severe anoxic encephalopathy. A serial study of electroencephalograms during 4 days showed sequential changes from periodic approximately 2 Hz spike activity to absence-like status (ALS) and then into a suppression-burst pattern. Intravenous administration of phenytoin had no effect on ALS. A small dose of intravenous diazepam reduced a suppression-burst pattern. We speculate that the ALS originates in the midline structures, spreading bilaterally and synchronously to the "dysfunctional" cortex; the sustained discharges were a manifestation of associated reticular lesions, and we believe that intravenous diazepam suppressed the spread of ALS to the "dysfunctional cortex," leading to the appearance of the suppression-burst pattern. The only limitation for definitive conclusions may be a lack of postmortem verification. Autopsy findings, however, could not have confirmed the dynamic changes that occurred during the 5 days before the patients death.