Pathophysiology of "reverse" edema in global cerebral ischemia.

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 obstruction 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.