Advances in Stent-Assisted Management of Intracranial Occlusive Disease and Cerebral Aneurysms

The effects of stenting and endothelial denudation on aneurysm and branch occlusion in experimental aneurysm models

BACKGROUND

Stents are increasingly used in the endovascular treatment of intracranial aneurysms. We studied the effects of stenting and endothelial denudation on aneurysm and branch vessel occlusion.

METHODS

Bilateral lingual bifurcation venous pouch aneurysms were created in eight dogs, surgically scraping the aneurysmal endothelial lining on one side. Both arteries were immediately stented using balloon-expandable stents. In four other dogs, a wide-neck carotid bifurcation aneurysm was created, with the vein pouch denuded or not (n=2 each), followed by immediate stenting. Results were compared using angiography and pathology at 10 days (n=2), 10 (n=8), and 20 weeks (n=2). Branch occlusion between initial and final angiograms was recorded. Pathological evaluation of aneurysms was studied, with attention to neointima formation at the aneurysm ostium and around branch vessel origins.

RESULTS

All stented and denuded lingual aneurysms were obliterated compared with two of eight lingual aneurysms that were stented alone (P=.007). None of the carotid bifurcation aneurysms became obliterated (0/4), but denuded aneurysms showed partial thrombosis (2/2). Of 68 total stent-covered branches, 5 (7%) were occluded and 17 (27%) had altered angiographic flow.

CONCLUSIONS

Stenting led to suboptimal results in the presence of an intact endothelial layer. Endothelial denudation can promote aneurysm occlusion when combined with stenting.

Effects of stenting the parent artery on aneurysm filling and gene expression of various potential factors involved in healing of experimental aneurysms

SUMMARY

Intracranial stents are increasingly used in the endovascular treatment of aneurysms, but very little is known regarding their effect on the cellular and molecular evolution of aneurysms. Bilateral venous pouch lateral wall carotid aneurysms were created in 20 dogs. All dogs then underwent angiography and balloon-expandable stenting of one aneurysm four to six weeks later. Fifteen dogs underwent aneurysm harvesting at one day (n=3), four days (n=4), seven days (n=3), and 14 days (n=5) for mRNA expression analysis, using axial sections taken from the aneurysm neck and fundus for RTPCR amplification of four cytokines or growth factors: TNF-a, TGF-b1, MCP-1, and PDGFBB; two adhesion molecules: VCAM-1 and PECAM-1; five matrix modifying agents; MMP- 2, 9, TIMPs 1, 3, 4, and two cellular markers: CD34 and a-SMA. Five other dogs, sacrificed at 12 weeks, were examined for extent of filling of the aneurysm neck with organized tissue and for neointima formation at the aneurysm ostium. Angiography was performed prior to sacrifice in all animals, and compared with initial studies. Eleven out of 20 stented aneurysms showed a favorable angiographic evolution, while none of the 20 nonstented aneurysms improved (p=0.001). Pathology showed partially occluded aneurysms, with neointima formation around the stent struts.Observed trends in mRNA expression, that stenting increased expression of genes involved in organization and neointima formation, agreed with experimental hypotheses, but differences between stented and non-stented aneurysms did not reach statistical significance. Parent vessel stenting was associated with angiographic improvement of aneurysm appearance. Modifications in mRNA expression patterns following stenting deserve further study to better establish potential molecular targets to promote aneurysm healing.