An aneurysm is an abnormally large bulge in the wall of a blood vessel, typically an artery. An aneurysm can occur in any part of the body, but is most common in the brain, aorta, legs, and spleen.
Some aneurysms appear to be congenital. Although the exact cause of aneurysm development remains unknown, increased blood pressure within the arteries increases the risk. Blood pressure may be increased due to high blood pressure or atherosclerotic disease. In this condition, plaque deposits build up in the arteries, restricting blood flow. In order to overcome this resistance, system pressure increases. This may weaken the arterial wall.
There are two main types of aneurysms. Saccular aneurysms present as blood-filled sacs attached to the artery wall. Also known as “berry” aneurysms because of their shape, they are at particular risk for rupture. The fusiform type is a general swelling of the artery radially and poses a lower risk of rupture. Intact aneurysms generally do not cause harm, but the potential for rupture is a risk.
Rupture of an aneurysm in the brain can cause a hemorrhagic stroke. Blood is diverted out of the artery, reducing pressure and flow volume in the vessels beyond the rupture site. At the same time, blood flow out of the rupture site increases intracranial pressure within the skull. This results in increased pressure applied to the exterior of the arteries, with reduced blood flow not only in the vessels beyond the rupture site, but within the entire brain. Without a supply of oxygenated blood, the brain tissue will die. Depending on the severity of the rupture, emergency surgery may be possible to repair the aneurysm and limit brain injury.
