Histologic abnormalities associated with gadolinium enhancement on MR in the initial hours of experimental cerebral infarction.

PURPOSE To determine the histologic changes associated with gadopentetate dimeglumine enhancement on MR images in acute focal cerebral ischemia.

METHODS In each of two baboons, a microcatheter was used to occlude partially the middle cerebral artery and reduce cerebral blood flow for approximately 3.5 hours. The catheter was then removed allowing reperfusion for approximately 3.5 hours. In two other baboons, cerebral blood flow was completely and irreversibly interrupted by injecting liquid adhesive into the middle cerebral artery. T2-weighted and serial enhanced T1-weighted MR images were obtained. Brain specimens were studied histopathologically.

RESULTS In the animals with incomplete and reversible reduction of cerebral blood flow, postcontrast T1-weighted images obtained during the initial 3 hours of ischemia showed focal areas of hypointensity. These areas were enhanced on later images. The areas of signal abnormality were subsequently found to be necrotic and were characterized by neuronal cytolysis and vascular "plugging." In the animals with complete and irreversible interruption of cerebral blood flow, no abnormal signal intensity or enhancement was observed. Histologic abnormalities were milder in these animals.

CONCLUSIONS Contrast enhancement on MR images in the initial hours of cerebral ischemia was associated with histologic evidence of tissue necrosis but was not associated with milder ischemic changes.