A New Model Of Unilateral Cerebral Cortical Draining Vein Occlusion In The Rabbits And Preliminary Observation Of Drug Intervention

Objective To create a rabbit model of acute cortical draining vein occlusion by bipolar electrocoagulation. In the rabbit models with acute cortical draining veins occlusion and ones with craniotomy only, Mannitol, tranexamic acid and the two combined were injected by vein to investigate whether they played an important role in promoting CVST(Cerebral venous sinus thrombosis).Methods (1) Thirty five rabbits were randomly divided into 3 groups. Group A (n=15), the operation group in which a cortial draining vein in the parietal lobe was permanently coagulated; Group B (n=15), the operation group in which both of cortial draining veins in the occipital lobe and parietal lobe were permanently coagulated;group C(n=5) with the craniotomy being performed and dura mater incised. The cortical vein was permanently sacrificed with bipolar electrocoagulation from the far to near, about 2 millimeter length vein was not obstructed with the 10 watt until the blood vessels turned to white, then to yellow but not charring, and the local region by electrocoagulation changed grey. The digtal substraction angiogrophy (DSA), the water content of the brain, the ratios of brain infarction, the expression of Caspase-3 and the formation of venous thrombus in cortical draining veins or anastomotic veins were obtained at an interval of 8 hours,24 hours,48 hours, espectively (n=5) for each subgroup after operation. Macroscopic examination and lightmicroscopy were compared with these data. (2)Thirty six rabbits were randomly divided into model group and sham-operated group. Then the two groups were divided into four subgroups randomly:mannitol treatment subgroup, tranexamic acid treatment subgroup,combined drug treatment subgroup, saline subgroup; observing the change of neurological function, testing hemorheology, measuring water content of damaged cortex tissue and the pathology.Results (1) The structure of wall cortical vein were damaged, and the lumen was extremely irregular, some closed, endothelial cells lossed, the thickness of the wall varied, even appeared to slit and hyaline degeneration, thrombosed after occlusion;but the endothelial cells of vein near the cortical veins occlusion with bipolar electrocoagulation lossed, and thrombosed;(2)The water contents in brain tissue of group B at 8h,24h,48h after operation were higher than those of group A(P<0.01);The ratio of brain infarction of group B was remarkably wider than those of group A(P<0.05). And the ratio of thrombosis in group B was much more than group A. The expression of Caspase-3 in the damaged cerebral cortex around cortical veins began at the time point of 8 hour after the cortical veins occlusion, and was significantly highest at the time point of 24 hour after the operation, but group C has nothing as above. (3)Each subgroup in Sham-operated group has no significant difference in water content of brain, the WC of mannitol therapy subgroup and combination therapy subgroup in model group had different degree decreases. Compared with saline subgroup, there was statistically significant difference for the whole blood high-shear, low shear whole blood, plasma viscosity, RBC aggregation index, erythrocyte electrophoresis time in mannitol, combination therapy subgroups of Sham-operation group and model group, but of tranexamic acid subgroup in the two groups were no statistically significant. there was no cerebral infarction and intracranial venous thrombosis in Sham-operated group, contrastely, cerebral infarction (13/18)and intracranial venous thrombosis (15/18)were seen in model group.Conclusion (1)The rabbit model by coagulating the cortical draining veins has higher successful rate,good stability and reproducibility, thus was an ideal model for studying the cortial draining vein occlusion. (2) In this study, high doses of mannitol and tranexamic acid may not result in CVST in normal animals, but they could have made blood concentration, making blood rheology changed greatly, but the possibility of inducing or further increasing the intracranial venous thrombosis may be relatively smaller After the cortical vein was damaged.