An aneurysm (AN-you-rizm) is an abnormal localized dilation or swelling of a blood vessel (a balloon-like bulge), which may cause massive bleeding, shock, or death if it ruptures (breaks open).

Why Are Aneurysms Called “Silent Killers”?

Aneurysms are sometimes called “silent killers” because they may go undetected for years until they break open. A segment of an artery * or vein * (less common) may weaken and begin to bulge, like an underinflated balloon whose air is squeezed from the ends to the middle. The bulge may grow slowly for years until one day the blood vessel wall gives way (ruptures). This rupture is a medical emergency that may lead to death. There are two major classes of aneurysms: aortic aneurysms, which occur in the major artery that carries blood away from the heart; and cerebral aneurysms, which occur in an artery in the brain.

Aneurysms of the aorta are virtually always caused by atherosclerosis (the buildup of plaque in arteries, which causes the arteries to lose elasticity and to harden). In the case of aortic aneurysms, a tiny tear develops within the inner layer of the aorta (the largest artery that carries blood away from the heart). Blood leaks through this tear into the middle layer of aortic tissue, causing the inner and middle layers to separate (dissect). Over time, this dissecting aneurysm results in an elongated blood-filled channel running up and down the aorta, which can break open, causing fatal bleeding.

Aortic aneurysms may arise in the abdominal portion of the aorta (abdominal aortic aneurysms) or the thoracic portion of the aorta (thoracic aortic aneurysms). In the United States, more than 15,000 people die annually due to rupture of an abdominal aortic aneurysm.

The most common aneurysm is the cerebral aneurysm, which is a stroke * . Cerebral aneurysms are also referred to as subarachnoid hemorrhage (SAH). SAH is a life-threatening event. More than 65 percent of individuals who experience SAH die as a result of the ruptured aneurysm. In the United States, about 30,000 cases of SAH are reported each year. Survivors of SAH are likely to experience severe and permanent disabilities.

False aneurysms are caused by trauma. They are shaped like small pouches on the vessel wall. Another type of aneurysm is called a berry. It too is shaped like a small pouch and is usually less than 1 inch in size. Berry aneurysms are commonly found in the vessels in the brain.

People with aneurysms develop bulges in the walls of an artery, vein, or other blood vessel. Top: A healthy artery. Bottom: Artery with an aneurysm.

People with aneurysms develop bulges in the walls of an artery, vein, or other blood vessel. Top: A healthy artery. Bottom: Artery with an aneurysm.
Illustration by Frank Forney © 2016 Cengage Learning®.

How Do Aneurysms Happen?

* . An increased incidence of aneurysms may be seen with certain conditions, such as syphilis or Marfan syndrome. Many times, however, an aneurysm develops without any known cause.

Abdominal aortic aneurysm affects many more men than women. It occurs more often in people who are older than 55, who are smokers, or who have high blood pressure. People with other family members who have had these types of aneurysms are more likely to develop the aneurysms themselves.

There usually are no signs of a growing aneurysm. In the case of abdominal aortic aneurysms, the affected person will sometimes feel pain in the abdomen * . A large aneurysm in the abdomen may press against the spine and cause back pain. The rupture of an aneurysm in an artery can kill a person quickly.

The rupture of a brain aneurysm constitutes a kind of hemorrhagic stroke. It is a medical emergency. Symptoms may include numbness, paralysis, stiff neck, vision loss, confusion, and loss of consciousness.

What Are the Signs and Symptoms of Aneurysms?

The signs and symptoms of an aneurysm depend on the location of the aneurysm and how large it is. Initially, for example, there may be no symptoms at all. As the aneurysm grows, symptoms may develop. For example, an expanding abdominal aortic aneurysm may cause severe pain deep in the individual's back or abdomen. The feet and legs may become cold and numb, due to interference with blood flow to the lower limbs. The physician may feel a pulsing mass in the individual's abdomen and may hear a characteristic sound while listening to the area with a stethoscope. If the abdominal aortic aneurysm should rupture, severe life-threatening symptoms will occur, including dizziness, fainting, rapid heart rate, nausea and vomiting, intensely severe abdominal and back pain, and eventually shock from blood loss. If the expanding aneurysm is located in the chest (thoracic aortic aneurysm), the individual may develop pain in the jaw, neck, upper back, or chest, as well as coughing, hoarse voice, and difficulty breathing.

The symptoms of an expanding brain aneurysm depend on where it is located. Possible symptoms of a growing brain aneurysm include the drooping of an eyelid, double vision, other vision impairment, pain in or behind the eye, an abnormally dilated pupil, and a numb or weak feeling on one side of the body or the face. If the brain aneurysm ruptures, then the signs and symptoms may include an unbearable headache, nausea and vomiting, stiff neck, unconsciousness, and other signs of stroke (difficulty swallowing, difficulty talking and understanding speech, confusion, dizziness, loss of balance, difficulty walking, weakness, or paralysis of limbs).

If the patient has a peripheral aneurysm, then the person might notice a pulsing bump in the neck, arm, or leg, as well as limb pain or muscle cramping with exercise; sores on the toes or fingers; or even gangrene due to loss of blood flow.

Monster of a Headache

R.E.M. was rocking its way through Europe during its 1995 “Monster” tour when drummer Bill Berry got a sudden, terrible headache and could not see. It turned out that Berry had a brain aneurysm, which was operated on immediately. The surgery was a complete success, and the band was able to finish touring with its excellent drummer.

Aortic aneurysms occur when a weakness develops in a part of the wall of the aorta. The aorta is the large blood vessel that carries oxygen-rich blood away from the heart to the rest of the body.

Aortic aneurysms occur when a weakness develops in a part of the wall of the aorta. The aorta is the large blood vessel that carries oxygen-rich blood away from the heart to the rest of the body.
llustration by Electronic Illustrators Group © 2016 Cengage Learning®.

How Do Doctors Diagnose and Treat Aneurysms?

Fortunately, many aneurysms can be detected before they rupture. Doctors often are able to feel the pulsating sensation of abdominal aneurysms through the skin. Aneurysms often cause subtle changes in how the heart sounds, and doctors might notice these changes when listening to the heart. The most reliable methods of checking for abdominal aneurysms are x-rays, ultrasound * exams, and other imaging techniques that can provide more detailed images of the body.

Cerebral aneurysms can be detected by sophisticated imaging techniques such as computed tomography (CT) scans and magnetic resonance imaging (MRI). Angiography, a process during which medical dye is injected into the body, is the most accurate method to detect and evaluate a cerebral aneurysm's location, size, and other characteristics.

Wait and see

If an aneurysm is discovered, sometimes a doctor may adopt a wait-and-see strategy, but this approach depends on the aneurysm's location, size, and the person's overall health. Small aneurysms might be checked every six months or so to confirm that they are not growing. Aneurysms usually grow slowly.


Sometimes surgery is required. One method involves removing the section that is bulging and replacing it with an artificial blood vessel. Another technique for repairing aortic aneurysms involves snaking a thin flexible wire up from an artery in the leg to the aneurysm, where a tube or coils are attached to the artery's walls on either side of the aneurysm.

The treatment of a cerebral aneurysm that has not ruptured is controversial. The aneurysm may require treatment depending on its size and location in the brain. Factors such as the patient's age, smoking history, and presence of other diseases place the patient at high risk for rupture of the aneurysm. However, brain surgery also carries considerable risk to the patient.

Ruptured cerebral aneurysm is considered a medical emergency, with the patient requiring treatment in an intensive care unit (ICU) setting before and after surgery to repair the ruptured blood vessel. Placing a coil in the ruptured vessel, also known as endovascular therapy, may also be an option for some patients with a ruptured cerebral aneurysm.

How Are Aneurysms Prevented?

The best suggestions for preventing the development of aneurysms include:

See also Arteriosclerosis/Atherosclerosis • Heart Disease: Overview • Intracranial Bleeding • Marfan Syndrome • Stroke • Vascular Diseases: Overview


Books and Articles

Mann, Douglas L., et al. Braunwald's Heart Disease. 10th ed. Philadelphia, PA: Saunders, 2015.

Ross, Maria. Rebooting My Brain: How a Freak Aneurysm Reformed My Life. San Francisco: Red Slice Press, 2012.


MedlinePlus. “Aneurysm.” U.S. Library of Medicine, National Institutes of Health. (accessed March 21, 2016).


American Heart Association. 7272 Greenville Ave., Dallas, TX 752314596. Toll-free: 800-242-8721. Website: HEARTORG (accessed March 10, 2016).

The Aneurysm and AVM Foundation. 3636 Castro Valley Blvd., Suite 3, Castro Valley, CA 94546. Telephone: 510-464-4540. Website: (March 10, 2016).

Brain Aneurysm Foundation. 269 Hanover St., Building 3, Hanover, MA 02339. Toll-free: 888-272-4602. Website: (accessed March 10, 2016).

* artery is a vessel that carries oxygenated blood from the heart to tissues in the body.

* vein is a vessel that carries unoxygenated blood to the heart. Veins have greater capacity and thinner walls than arteries and contain valves that prevent blood from flowing backward and away from the heart.

* stroke is a brain-damaging event usually caused by interference with blood flow to a region of the brain. A stroke may occur when a blood vessel supplying the brain becomes clogged or bursts, depriving brain tissue of oxygen. As a result, nerve cells in the affected area of the brain, and the specific body parts they control, do not properly function.

* congenital (kon-JEH-nih-tul) means present at birth.

* abdomen (AB-do-men), commonly called the belly, is the portion of the body between the thorax (THOR-aks) and the pelvis.

* ultrasound exams or sonograms use inaudible sound waves that can be generated by special equipment, and the reflections, or echoes, of the sound waves are used to produce an image or picture of on organ or tissue. This technique can help doctors to diagnose an illness and determine how best to treat the patient.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)