Ischemic Brain Tissue Water Content: CT Monitoring during Middle Cerebral Artery Occlusion and Reperfusion in Rats1

To prospectively perform computed tomography (CT) in rats to determine whether ischemic edema can be reversed by using early arterial reperfusion.This study was approved by the local animal protection committee. A suture model was used to occlude the right middle cerebral artery (MCA) in rats for 1, 2, 3, or 4 hours. X-ray attenuation of the brain was measured directly before reperfusion and repeatedly during reperfusion for up to 24 hours. Infarct volumes were determined with triphenyltetrazolium chloride staining. Means of attenuation and infarct volume were compared between hemispheres and groups with a paired t test and analysis of variance. Mixed linear models were applied to compare attenuation among groups over time.During MCA occlusion, attenuation decreased to 69.3 HU +/- 1.9 (standard deviation) after 1 hour (n=12), 66.6 HU +/- 2.0 after 2 hours (n=10), 65.4 HU +/- 2.9 after 3 hours (n=11), and 64.1 HU +/- 1.8 after 4 hours (n=9) (P<.0001). After reperfusion, attenuation remained stable in the 1-hour occlusion group (P=.16) but further and steadily declined in the 2-, 3-, and 4-hour occlusion groups (P<.001). Attenuation during reperfusion in the 1-hour occlusion group differed significantly from that in the 2-, 3-, and 4-hour occlusion groups.CT is able to help monitor ischemic edema after MCA occlusion and reperfusion. Ischemic brain edema was not consistently reversible with reperfusion, even after 1 hour of occlusion, and further increased with reperfusion induced at 2 hours or later.