Prediction of outcome in severe head injury based on recognition of sleep related activity in the polygraphic electroencephalogram.

This study shows that the continuing presence of activity similar to normal sleep in the EEG in conjunction with the EEG polygraph (EEGP) can be used to determine the severity of brain damage after head injury. Recordings were taken within seven days of head injury from 154 unselected patients after resuscitation and emergency surgery. Sixteen patients with ongoing seizures were excluded. In the remaining 138 patients the presence of activity in the EEG, EEGP, or both, which can also be recognised in normal alertness and sleep, was noted. Particular attention was paid to the presence or absence of arousal related phasic activity involving EEG, motor, and autonomic changes. The traces were allocated to one of five groups: group 1, wakeful traces with normal alpha in at least one hemisphere; group 2, sleep-like traces with K complexes responsive to stimulation; group 3, traces with phasic activity related to abnormal spontaneous arousal including EEG changes; group 4, traces with abnormal spontaneous arousal activity without EEG changes; group 5, traces with no spontaneous arousal activity. The mean follow up was 21.5 months. Groups 2 and 3 were significantly associated with a good outcome and group 5 with death or a vegetative state. Comparison between the EEG/EEGP findings and the Glasgow coma scale at the time of the recording showed the EEG/EEGP to be the better predictor of outcome, particularly for individual patients.