EEG and evoked potentials in comatose patients with severe brain damage

EEGs and evoked potentials were recorded in 76 deeply comatose and unresponsive patients with traumatic or non-traumatic cerebral damage. Spontaneous EEG activity was absent in 37 of the patients on the initial examination. The cortical somatosensory evoked potentials were invariably absent in these patients as were the visual evoked potentials. Brain-stem evoked potentials were abnormal, either lacking all waves or with only wave I or II present. Cerebral angiography performed in 33 of the patients within minutes to a few hours after the neurophysiological examination verified an established brain death, showing full intracerebral circulatory arrest in all. Spontaneous EEG activity was initially present in 32 patients on the first examination, 20 of whom had bilaterally abolished cortical somatosensory potentials. Ten of the patients died a few hours after the initial examination, another 10 were followed for 2-3 days and subsequently developed electrocortical silence (ECS). Twelve of the patients with spontaneous EEG activity had preserved cortical somatosensory potentials, either uni- or bilaterally. The only two who survived were found in this group. In the patients followed with multiple recordings over a few days, the first parameter to indicate a grave prognosis was always disappearance of the cortical somatosensory potentials bilaterally, which generally occurred hours, and sometimes a day or two, before cessation of the spontaneous EEG activity. EEG records from 7 patients did not meet the technical criteria of ECS; all, however, had abolished cortical somatosensory potentials bilaterally, and none in this group survived.