An aneurysm (or aneurism) is a localized dilation or ballooning of a blood vessel by more than 50% of the diameter of the vessel, much like a bulge on an over-inflated innertube. It can lead to instant death.
Although discussions about aneurysm tend to focus on the brain, aneurysms can occur anywhere there is a blood vessel. They are most common in arteries, especially in the aorta — the body's largest artery. The aorta resembles a garden hose in thickness and runs from the heart down the center of the chest and abdomen, eventually splitting off into two arteries, one that serves each leg.
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). The larger an aneurysm becomes, the more likely it is to burst.
There are two types of aneurysms:
True Aneurysms
A true aneurysm involves an outpouching of all three layers of a blood vessel: the intima, the media, and the adventitia. True aneurysms can be due to congenital malformations, infections, or hypertension.
False Aneurysms
A false aneurysm, also known as a pseudoaneurysm, involves an outpouching of only the adventitia.
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