An aneurysm that ruptures in an artery of the brain causes a stroke. It is not known why aneurysms occur in some people and not others. People with the greatest risk are white men over age 55. Aneurysms are among the top ten causes of death among this group. Brain artery aneurysms affect both men and women at younger ages.
Men are three times more likely to have abdominal aortic aneurysms than women.
Aneurysms appear to be caused by a congenital weakness in the vessel wall, high blood pressure, arteriosclerosis, injuries, infection, smoking, and other diseases. Most aortic aneurysms grow slowly. Over many years, the walls slowly stretch and enlarge like a balloon. The normal aorta is about as wide and as tough as a garden hose. An aneurysm in this blood vessel can grow to the size of an orange before it ruptures.