Frontal Blood Flow Changes in Recovery from Coma

Two-dimensional studies of cortical blood flow were conducted in 20 closed head injury patients in a comatose state and subsequently in 9 patients as they recovered to an awake and responding state. Comatose patients showed a reduction of frontal flow compared to the resting pattern observed in age matched normal volunteers. In most patients the normal anterior-to-posterior flow gradient was reversed. Increases in global flow, while in coma, tended to exaggerate this reversal. Patients who survived showed a normalization of the regional flow pattern as they regained consciousness. The marked reduction of frontal blood flow in the comatose state was independent of locus of injury as determined by computed tomography (CT) scan data. Combined with previous CBF studies of sensory and cognitive activation, these findings suggest that frontal reduction may be a nonspecific effect of any state or condition involving reduced directed mental activity. This, in turn, raises questions about recent interpretations offered for frontal CBF reduction in psychiatric disease.