What Causes Aneurysms?

The most frequent cause of aneurysm is atherosclerosis, a condition in which fats and other substances accumulate in the artery lining (see Atherosclerosis for more information). The death of cells in the region affected by the deposits can cause thinning and weakening of the vessel wall, which can lead to the formation of an aneurysm.

Atherosclerotic aneurysms have taken over from syphilitic aneurysms as the major cause of aortic aneurysm. However, although syphilis has now become uncommon; it may still give rise to the condition. During the latter stages of the disease (around 15-30 years after the first signs), the infection spreads to the portion of the aorta nearest the heart, weakening the blood vessel wall and producing a thoracic aortic aneurysm.

Another type of aneurysm is known mycotic aneurysm, which occurs as a complication of bacterial infection of the heart lining or heart valves. This may lead to inflammation that may damage the vessel wall and lead to the development of an aneurysm.

Although most aneurysms are caused by conditions that develop over time, there are also a number of congenital aneurysms that are present from birth and are not usually noticeable till later in life.