The changes of dural microcirculation after venous sinus hypertension in rats: A dynamic observation

Objective: To investigate the mechanisms of dural arteriovenous fistula (DAVF) by observing the changes of dural microcirculation after venous sinus hypertension in rats. Methods: One hundred ten rats were randomly allocated into experimental (n = 85) and control groups (n = 25). Superior sagittal sinus and left transverse sinus were occluded in the experimental group. At the same time, the right common carotid artely and external jugular vein anastomosis were performed, and venous sinus hypertension was induced. Then the dural microcirculation of 3 rats in the experimental group and 1 in the control group was evaluated on day 7, 14, 21, 28, 40, 60, and 90 respectively after the procedure, and the changes of vascular numbers and diameters at the levels of superior sagittal sinus 1 mm aside and 1 mm in the vertical direction that could be cut were evaluated. Results: The dura mater did not show angiogenesis in the early dural venous sinus hypertension (7 days) in rats, and only after the dural venous sinus hypertension had existed for a period of time (14 days) that the angiogenesis would appear. There were no significant differences between the two groups on the numbers of blood vessels 90 days after venous sinus hypertension (P > 0.05). The opening of arteriovenous direct passages in the capillary network could be observed in the experimental group; and the passages that blood passed through were direct and short (21 days). The formation of DAVF was observed on day 28 in the experimental group, and its morphology and structure was similar to that of the normal arteriovenous shunt. The only difference was that the linked blood vessels become thick and they no longer to be capillaries. Conclusion: In the initial stage of venous sinus hypertension, the angiogenesis was active, but it was attenuated and disappeared in late the stage. The analysis from the position and structure of fistula opening showed that it was likely that it was gradually evolved from the original weak position of blood vessel.