Alpha-coma. Electroencephalographic, clinical, pathologic, and etiologic correlations.

"Alpha-coma" denotes the conjunction of clinical coma with an electroencephalographic pattern resembling that of normal wakefulness and predominantly consisting of alpha activity. Clinical, EEG, and pathologic data from 13 patients with this syndrome were reviewed. The patients were divided into two groups, based on the pathogenesis of their conditions. The first group consisted of eight patients with brain stem strokes, and the second group consisted of five patients with diffuse hypoxic encephalopathy resulting from cardiac or pulmonary arrest. There were some differences between the EEGs of the two groups. In the first group, the alpha pattern was located more posteriorly, showed more variability and reactivity, and was more persistent in sequential recordings. In the second group, the alpha activity was transient and showed little reactivity. In both groups, this pattern indicated a poor prognosis for survival.