Edema in Global Cerebral

A small percentage of patients who suffer a global cerebral hypoxic/ischemic event develop reversal of the normal density relationships of gray and white matter on CT. CT and pathologic findings in the three cases presented indicate that this phenomenon appears to result from distension of deep medullary veins secondary to partial obstruc-tion of venous outflow from elevated intracranial pressure. The "reverse " edema sign indicates a severe hypoxiC/ischemic injury to the brain and has a poor clinical prognosis. A peculiar reversal of the normal densities of gray and white matter occurs in a small percentage of patients who have suffered a diffuse hypoxic/ischemic injury to the brain. This phenomenon has been previously termed the "reversal " sig;, [1). The purpose of this article is to (a) report three patients who demonstrated such a finding on CT acquired after a diffuse hypoxic/ischemic insult; (b) describe the pathologic basis for its appearance; and, (c) propose an etiologic mechanism by which this change occurs. Case Report