An aneurysm occurs when part of an artery wall weakens, allowing it to abnormally balloon out or widen.
The causes of aneurysms are sometimes unknown. Some people are born with them. They can also be hereditary. Aortic disease or an injury may also cause an aneurysm.
A family history of aneurysm may increase your risk for developing an aneurysm. Other risk factors include high blood pressure, high cholesterol and tobacco use.
Aneurysms can occur in any artery, but the most common are:
- Aortic aneurysm occurs in the main artery carrying blood from the heart to the body.
- Cerebral aneurysm occurs in an artery of the brain.
- Popliteal artery aneurysm occurs in the artery behind the knee.
- Mesenteric artery aneurysm occurs in the artery that supplies blood to the intestine.
- Splenic artery aneurysm occurs in an artery of the spleen.
Learn more about the different types of aneurysms.
Symptoms and diagnosis
Aneurysms can develop over many years and often have no symptoms.
If an aneurysm expands quickly or ruptures, symptoms can vary based on the location and may develop suddenly. Depending on the site of the aneurysm, symptoms can include:
- Headache
- Pain in abdomen or back
- Pulsating abdominal mass
- Blue coloration [cyanosis] of lower extremities
- Dizziness
- Vision changes
- Confusion
- Fatigue
- Hoarseness
- Difficulty swallowing
- High-pitched breathing sound
- Swelling in the neck
- Chest or upper back pain
- Nausea and vomiting
- Sense of impending doom
- Shock [low blood pressure, rapid heart rate, clammy skin, decreased awareness]
Your doctor can use an angiogram, CT scan or ultrasound test to diagnose an aneurysm.
Treatment and prevention
An aneurysm can become a medical emergency. Call 911 or your local emergency number and seek immediate medical attention if you or someone you know is having aneurysm signs and symptoms.
If you’ve been diagnosed with an unruptured aneurysm, work with your doctor to monitor any changes to the aneurysm. Your condition may require regular checkups depending on the aneurysm’s size and location.
Some aneurysms may require surgery to reinforce the artery wall with a stent. When the aneurysm has ballooned out the side of the blood vessel, a clip or coiling procedure may close off the area.
Lower your risk
To lower your risks for an aneurysm, maintain a healthy lifestyle throughout your life. Some steps include:
- Controlling high blood pressure
- Eating healthy foods
- Getting regular physical activity
- Quitting smoking or using tobacco in any form
Written by American Heart Association editorial staff and reviewed by science and medicine advisers. See our editorial policies and staff.
Overview
The Dangers of Brain Aneurysm
Aneurysms can lurk without symptoms, but screening can save lives.
Click here for an infographic to learn moreA brain aneurysm [AN-yoo-riz-um] is a bulge or ballooning in a blood vessel in the brain. An aneurysm often looks like a berry hanging on a stem.
A brain aneurysm can leak or rupture, causing bleeding into the brain [hemorrhagic stroke]. Most often, a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. This type of hemorrhagic stroke is called a subarachnoid hemorrhage.
A ruptured aneurysm quickly becomes life-threatening and requires prompt medical treatment.
Most brain aneurysms, however, don't rupture, create health problems or cause symptoms. Such aneurysms are often detected during tests for other conditions.
Treatment for an unruptured brain aneurysm may be appropriate in some cases and may prevent a rupture in the future. Talk with your health care provider to ensure you understand the best options for your specific needs.
Symptoms
Ruptured aneurysm
A sudden, severe headache is the key symptom of a ruptured aneurysm. This headache is often described as the "worst headache" ever experienced.
In addition to a severe headache, common signs and symptoms of a ruptured aneurysm include:
- Nausea and vomiting
- Stiff neck
- Blurred or double vision
- Sensitivity to light
- Seizure
- A drooping eyelid
- Loss of consciousness
- Confusion
'Leaking' aneurysm
In some cases, an aneurysm may leak a slight amount of blood. This leaking may cause only a sudden, extremely severe headache.
A more severe rupture often follows leaking.
Unruptured aneurysm
An unruptured brain aneurysm may produce no symptoms, particularly if it's small. However, a larger unruptured aneurysm may press on brain tissues and nerves, possibly causing:
- Pain above and behind one eye
- A dilated pupil
- A change in vision or double vision
- Numbness of one side of the face
When to see a doctor
Seek immediate medical attention if you develop a:
- Sudden, extremely severe headache
If you're with someone who complains of a sudden, severe headache or who loses consciousness or has a seizure, call 911 or your local emergency number.
Brain aneurysms develop as a result of thinning artery walls. Aneurysms often form at forks or branches in arteries because those areas of the vessels are weaker.
Although aneurysms can appear anywhere in the brain, they are most common in arteries at the base of the brain.
Mayo Clinic Minute: What is an aneurysm?
An aneurysm is an abnormal bulge or ballooning in the wall of a blood vessel.
"A proportion of these patients will go on to have a rupture. And the challenge with rupture is that it's unpredictable."
Dr. Bernard Bendok says a ruptured aneurysm is a medical emergency that can cause life-threatening bleeding in the brain.
"The typical presentation is somebody who has the worst headache of their life."
Fast treatment is essential. It includes open surgery, or less-invasive options, such as sealing the ruptured artery from within the blood vessel with metal coils and/or stents.
Dr. Bendok says 1 to 2 percent of the population have aneurysms, and only a small percentage of that group will experience a rupture. People who have a family history of aneurysms, have polycystic kidney disease, connective tissue disease, and people who smoke are at increased risk of rupture, and should consider screening. If a rupture happens, fast treatment can save lives.
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Causes
The causes of most brain aneurysm are unknown, but a range of factors may increase your risk.
Risk factors
A number of factors can contribute to weakness in an artery wall and increase the risk of a brain aneurysm or aneurysm rupture. Brain aneurysms are more common in adults than in children. They're also more common in women than in men.
Some of these risk factors develop over time, while others are present at birth.
Risk factors that develop over time
These include:
- Older age
- Cigarette smoking
- High blood pressure
- Drug abuse, particularly the use of cocaine
- Heavy alcohol consumption
Some types of aneurysms may occur after a head injury or from certain blood infections.
Risk factors present at birth
Some conditions that are present at birth can be associated with an elevated risk of developing a brain aneurysm. These include:
- Inherited connective tissue disorders, such as Ehlers-Danlos syndrome, that weaken blood vessels
- Polycystic kidney disease, an inherited disorder that results in fluid-filled sacs in the kidneys and usually increases blood pressure
- Narrow aorta [coarctation of the aorta], the large blood vessel that delivers oxygen-rich blood from the heart to the body
- Brain arteriovenous malformation [AVM], in which the arteries and veins in the brain are tangled, interrupting blood flow
- Family history of brain aneurysm, particularly a first-degree relative, such as a parent, brother, sister or child
Complications
When a brain aneurysm ruptures, the bleeding usually lasts only a few seconds. However, the blood can cause direct damage to surrounding cells, and the bleeding can damage or kill other cells. It also increases pressure inside the skull.
If the pressure becomes too high, it may disrupt the blood and oxygen supply to the brain and loss of consciousness or even death may occur.
Complications that can develop after the rupture of an aneurysm include:
- Re-bleeding. An aneurysm that has ruptured or leaked is at risk of bleeding again. Re-bleeding can cause further damage to brain cells.
- Narrowed blood vessels in the brain. After a brain aneurysm ruptures, blood vessels in the brain may contract and narrow [vasospasm]. This condition can cause an ischemic stroke, in which there's limited blood flow to brain cells, causing additional cell damage and loss.
- A buildup of fluid within the brain [hydrocephalus]. Most often, a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. The blood can block the movement of fluid that surrounds the brain and spinal cord. As a result, an excess of fluid puts pressure on the brain and can damage tissues.
- Change in sodium level. Bleeding in the brain can disrupt the balance of sodium in the blood. This may occur from damage to the hypothalamus, an area near the base of the brain. A drop in blood sodium levels can lead to swelling of brain cells and permanent damage.