MICROCIRCULATION AFTER CEREBRAL VENOUS OCCLUSIONS AS ASSESSED BY LASER-DOPPLER SCANNING

Research on cerebral venous circulation disturbances (CVCDs) has been Limited partly by the paucity of animal models that produce consistent Venous infarction. Occlusion of two adjacent cortical veins in rats b y means of a photochemical thrombotic technique provides a minimally i nvasive, clinically relevant, and reproducible model suited to study t he pathophysiology of CVCDs. In this study, the effects of venous occl usion on regional cortical blood flow and the brain damage that ensues were evaluated. Cortical vein occlusion was induced by photoactivatio n of rose bengal via 100-mu m fiberoptic illumination. The cerebral ve nous flow pattern was examined using fluorescence angiography until 90 minutes after venous occlusion, and regional cerebral blood flow (rCB F) was determined at 48 locations by using laser Doppler scanning. His tological damage was assessed 48 hours after vein occlusion. Occlusion of two cortical veins (Group T; seven animals) was compared with sing le-vein occlusion and its ensuing brain damage (Group S; five animals) and with sham-operated control (five animals). An rCBF reduction occu rred 30 minutes after occlusion in Group T and was more extensive than the decrease in Group S after 60 minutes. Observation frequency histo grams based on local CBF data obtained in Group T demonstrated that lo cal CBF at some sites decreased to a level below the ischemic threshol d within 90 minutes. Six of the seven rats in Group T had a growing ve nous thrombus with extravasation of fluorescein. The resulting infarct ion was significantly larger in Group T (9.8 +/- 4.5% of the hemispher ic area) than in Group S (only 3 +/- 1.5% of the hemispheric area).In conclusion, microcirculation perturbations occur early after venous oc clusion and result in the formation of a venous thrombus accompanied b y local ischemia and severe venous infarction. The extent of vein occl usion determines the resulting brain damage. Based on the results of t his study, the authors conclude that CVCDs may be attenuated by preven tion of venous thrombus progression together with the use of protectiv e measures against the consequences of ischemia.