[Experimental intracranial venous microsurgery. Bypass of the sagittal sinus for arterial or venous repair and preoperative measurement of the cerebral impedance in the dog].

By-passes of the sagittal sinus-which is 2,5 mm in diameter-were carried out with autogenous arterial or venous grafts, in 34 dogs, using the classical microtechniques (operative microscope, micro-instruments, micro-sutures...). Controls were done both 1 degree by angiography (direct sinography was the only convenient procedure to visualize the sinus and the by-pass) during survival, and 2 degrees by anatomical and histological examination after sacrifying the animals, on an average the 40th post-operative day (from the 10th to the 75th day). The early patency rate (within the first post-operative month) was 76 p. 100. All cases of early thromboses, which affected especially venous autografts, were related to technical insufficiencies. The late patency rate (after a one month follow-up) was only 64 p. 100, because of the secondary occlusion of some arterial autografts. All these late thromboses were related to an extensive fibrosis of the arterial wall.