Revised EEG coma scale in diffuse acute head injuries in adults

The validity of a recently published EEG grading scale applied to patients with acute head injuries has been investigated. This scale is based on 15 individual grades and subdivisions and 3 major groups: 4 patterns are benign regarding survival, 4 are of uncertain significance and 7 patterns are prognostically malignant. The evaluation was performed in 90 adult patients with acute head injuries in whom EEGs obtained during the 36 hours after the injury were evaluated retrospectively without knowing the clinical details or the outcome. By employing previously reported definitions it was possible to allocate EEG abnormalities in all cases. The assumption was made that at the time of the EEG investigation the impact of the head injury on cerebral function was already established. All patients displaying 'benign' patterns survived. 'Uncertain' patterns were the most common ones and in patients with these the reactivity of EEG activity was more important for prognosis than the quality of the background activity. All but 3 of the patients with a 'malignant' pattern died, and the survivors remained in a vegetative state. There was a correlation between the EEG findings and the Glasgow Coma Scale score on admission and also with the results of computerized tomography of the brain. In those patients who died there was no significant relationship between EEG signs and autopsy findings. Repeated EEGs are always desirable with severe head injuries but the results of this study suggest that useful prognostic information can be obtained from an EEG recorded within 36 hours after the head trauma.