What causes an aneurysm?

What causes an aneurysm? So that's a good question. I think we know some risk factors for aneurysm and development. Mostly it's to do with the weakness in the anterior wall. So there are three layers to an artery, the intima, the media, which is the thick muscular layer, and then the anterior adventitia. And we think it's to do with cross-linking of collagen and then a lack of strength in that wall which then leads to it expanding and things like hypertension, so high blood pressure from the inside pushing out, obviously exacerbates this. I think it's fair to say that it's multifactorial and we don't absolutely understand the final common pathway but there are certainly some risk factors which are applied to normal peripheral vascular disease, which tends to cause stenosis and occlusions, which also apply to aneurysms. So smoking is a very good example of that, and smoking is linked to both aneurysmal development and progression and growth of aneurysms. One of the things I think we don't understand is that if one finds a small aneurysm in a patient, what can be done to prevent that growing? And there's some simple things like healthy diets, stopping smoking, controlling blood pressure, but we don't have a tablet or an intervention to stop a small aneurysm becoming a large aneurysm.