[A study on histological changes of the intracranial arteries after permanent clipping or ligation.--Part II. Autopsy cases of aneurysmal neck clipping (author's transl)].

Local changes after neck clipping of cerebral aneurysms were studied histopathologically with light microscope in 12 autopsy cases. Seven of them were treated surgically with Yaşargil clips and 5 were treated with Heifetz clips. Another 5 aneurysmal cases, who died without surgery, were studied as the control group. At autopsy, the circle of Willis was fully exposed and meticulously dissected, and the clipped aneurysm was removed en bloc and embedded whole into a paraffin block after the aneurysm clip was removed. The specimen was examined histopathologically in longitudinal serial sections. Time interval between the operation and autopsy ranged from 6 days at the shortest to 11 months at the longest. All cases were congenital berry aneurysms, which showed defects of the tunica media and the internal elastic lamina. The arterial wall between the blades of aneurysm clip showed segmental arterial wall necrosis in 4 (47%) out of 7 cases in the Yaşargil clip group, and in all 5 cases (100%) in the Heifetz clip group. The necrotic change was the strongest at both edges of the blades of the aneurysm clip in the Yaşargil clip group, whereas in the Heifetz clip group the worst changes was found at the mid-convexity of the blades. This is probably due to the different shape and width of the blade of these aneurysm clips. The blade of the Heifetz clip is wider than the blade of the Yaşargil clip, and its convex, almost cylindrical surface is turned toward the vessel, causing a wider ischemic area of the arterial wall with the strongest closing force at the mid-convexity. In the Yaşargil clip group, the degree of arterial wall necrosis was well correlated to the time interval after the clipping. The Heiftz clip group showed arterial wall necrosis even within the 7 days following the operation, and the degree of the necrosis did not show a correlation to the time interval. Definite reactive granulation tissue was not observed until 1 month after the operation, and thereafter the degree of granulation in both groups was proportional to the time interval after the operation. After 3 months following the operation, the blades of the aneurysm clips were covered completely with the granulation tissue and it seemed impossible for the aneurysm clip to slip out at this stage. Up to 14 days after the operation, the aneurysmal lumen was filled with mural, red thrombus and irregular intimal proliferation. After one month following the operation, this was filled with diffuse massive intimal thickening and organized thrombus. After 3 months, intimal thickening filled the aneurysmal lumen almost completely.