Histological and Neurological Outcomes after Transient and Permanent Middle Cerebral Artery Occlusion in Rats

Background and Purposes: Most studies of middle cerebral artery (MCA) occlusion have concentrated on the acute phase of ischemia. Nevertheless, it has been suggested that the focal ischemic changes produced by MCA occlusion constitute a dynamic process in which several pathophysiological events occur over an extended period. Moreover, reperfusion of an occluded artery might be expected to exacerbate cerebral edema after focal stroke. The purposes of the present investigation were (1) to investigate the histological and neurological changes of rat brain over a long period after MCA occlusion, and (2) to examine the effect of reperfusion on brain edema. Methods: Forty-seven male Sprague-Dawley rats were subjected to 60 minutes or permanent right MCA occlusion. Infarct volume, edema and neurological score were measured 24 hours or 28 days after transient or permanent MCA occlusion. Results: Infarct volumes were significantly decreased (p＜0.01) after 28 days of recovery compared with that after 24 hours of recovery in both transient and permanent groups. A significant reduction (p＜0.01) in cerebral edema was found at 28 days after transient MCA occlusion. At 28 days after permanent MCA occlusion, cerebral shrinkage was observed. Moreover, no significant differences in infarct size and cerebral edema were seen between permanent and transient MCA occlusion after 24 hours of surgery. Conclusions: This study demonstrates that infarct volume and cerebral edema were significantly decreased after 28 days of recovery and cerebral edema after focal stroke is independent of reperfusion status.