Category A - full version without watermark 720x576 (check terms and conditions at www.teledesign.de) The embed version with watermark is free of charge. - Description: An aneurysm a localized, blood-filled dilation of a blood vessel caused by disease or weakening of the vessel wall. Aneurysms most commonly occur in arteries at the base of the brain (the circle of Willis) and in the aorta (the main artery coming out of the heart, a so-called aortic aneurysm). As the size of an aneurysm increases, there is an increased risk of rupture, which can result in severe hemorrhage or other complications including sudden death. Aneurysms are treated by endovascular techniques like angioplasty with stent.