gms | German Medical Science

Objective: Treatment of ruptured cerebral aneurysms include clipping and endovascular therapies. To determine the long-term results of these therapeutic strategies, the vessel wall reaction close to the former aneurysm can be histologically studied according to the assumption that an intact endothelial layer over the former aneurysm neck constitutes complete vessel wall reconstruction and thereby obliteration of the aneurysm.

Methods: We created aneurysms of the common carotid artery in 40 rabbits with elastase. 5 animals served as controls, 5 animals each were assigned to one of the groups: porous stents alone, polyurethane covered stentgrafts, porous stents and coil through the meshes. 10 animals each were treated with coiling and operative clipping. All animals were observed for 6 months followed by final 3D angiography and histological analyses. In 5 of the Clip and Coil groups electron microscopy was performed.

Results: Porous stents alone did not reliably obliterate the aneurysm, whereas stentgrafts did, however, in-stent stenosis of up to 60% was present due to neointimal proliferation. Stenting with subsequent coiling resulted in compaction of the coils although dense packing was possible. In the coiled aneurysms, the dome was completely occluded with fibrinous and collageneous extracellular matrix and granulation tissue, however, the neck and clefts within the coiled aneurysm were still perfused, even in angiographically completely occluded aneurysms. Some of the coil loops lay bare within the vessel with fresh thrombus present on their surface, a neoendothelialization was not present. In the clipped aneurysms, the blades of the clip had tightened the opposing healthy vessel walls to each other with a thin layer of endothelial lining bridging the two attached vessel walls thereby completely obliterating the aneurysm and reconstructing the healthy vessel wall.

Conclusions: On the one hand the study demonstrates possible shortcomings and problems of emerging “Stent-techniques” to treat intracerebral aneurysms, on the other hand our results prove that clipping of an aneurysm results in complete and stable aneurysm obliteration with reconstruction of the vessel wall while coiling does not. Our data are in agreement with the clinical literature in that the risk of a re-bleed is higher in coiled than in clipped aneurysms. Whether or not this increased risk is counterbalanced by the better immediate outcome following endovascular treatment still remains a matter of debate.