Sleep cycle in patients in a state of permanent unconsciousness

Since the recent diagnostic criteria for persistent vegetative state (PVS) require the presence of a sleep-wake cycle, certain patients in similar conditions should be excluded from PVS. Since the diagnosis of PVS might correlate with legal issues, an accurate definition is necessary. To clarify the clinical significance of a sleep-wake cycle, 12 patients in a state of permanent unconsciousness after brain damage were clinically and electrophysiologically reviewed. In addition to routine EEG, evoked potentials and MRI, the simultaneous recordings of EEG and patients by videotape were performed for 24 hours. Four patients who showed severe brain stem damage did not show a sleep-wake cycle. In the other eight patients, a sleep-wake cycle was observed. However, among these patients there was no obvious difference in their clinical status. Although these data suggest that the presence of a sleep-wake cycle might reflect the brain stem damage, it is considered that the presence of a sleep-wake cycle might be unnecessary for the diagnostic criteria for PVS. Further study of various forms of brain damage will provide better understanding of the significance of the presence of a sleep-wake cycle.