Gray matter enhancement: a computerized tomographic sign of cerebral hypoxia.

An important computerized tomographic (CT) pattern is described, in which selective enhancement of cerebral gray matter occurs after intravenous administration of contrast medium. Analysis of 76 cases displaying the enhancement pattern revealed that the phenomenon occurs in diseases characterized by hypoxia, and may be attributed to regional vascular dysautoregulation. Eighty percent of these patients had primary cerebrovascular disease (infarctions or transient ischemic attacks); 20% with other disorders also had evidence of cerebral ischemia or infarction. When hypoxia progressed to infarction, the enhancement was accompanied by one or more parenchymal areas of decreased density. However, in transient ischemic attacks, it occurred without other parenchymal abnormality and represents the first recognized CT sign of cerebral hypoxia. Enhancement was observed within 3 weeks of onset in 80% of cases, but in 20% it persisted for up to 4 months, indicating a protracted state of dysautoregulation.