An Overview of Brain Aneurysms

A brain aneurysm is characterized by a bulging area in the wall of an artery in the brain. The defect can produce pressure on nearby structures, causing problems such as double vision or changes in your pupil size. If you have a brain aneurysm, the biggest concern is that it could bleed. Whether it slowly leaks blood or rapidly pours blood into the surrounding brain regions, a brain aneurysm can cause serious long-term neurological damage.

Brain aneurysms range in size, with some being small (millimeters) and some quite large (centimeters). Genetics play a role in the development of brain aneurysms, but some occur without any identifiable cause.

Treatment of brain aneurysms includes medical management, surgery, and rehabilitation.

brain aneurysm

Verywell / Laura Porter


Brain aneurysms generally affect adults over the age of 30. While they are rarely found in children or adolescents, they can occur at any age. A brain aneurysm can cause dramatic symptoms if it ruptures (bursts), and mild symptoms or no symptoms at all if it doesn't rupture.

These aneurysms can grow slowly or rapidly, or may remain unchanged throughout your life.

A brain aneurysm can rupture regardless of size or growth rate.

Unruptured Brain Aneurysms

Most of the time, unruptured brain aneurysms do not cause any symptoms. Symptoms can occur when an unruptured brain aneurysm exerts pressure on a nearby nerve or blood vessel in the brain. The effects are usually subtle and may occur intermittently, but they can be constant or progressively worsen.

Effects that can occur due to an unruptured brain aneurysm include:

  • Peripheral vision loss
  • Double vision
  • A droopy eyelid on one side
  • Changes in the size of one pupil
  • Headaches
  • Numbness or weakness on one side of the face or body
  • Seizures

Brain aneurysms that do not cause any pain or neurological symptoms are called asymptomatic brain aneurysms.

Ruptured Brain Aneurysms

Bleeding brain aneurysms can cause subarachnoid hemorrhages (blood in the area between the meninges and the brain) or hemorrhagic strokes (bleeding in the brain tissue).

The symptoms of a ruptured brain aneurysm include:

  • Throbbing headaches—characteristically described as "the worst headache of my life"
  • Paralysis or other stroke symptoms
  • Vision changes
  • Loss of consciousness
  • Seizures
  • Rapid decline and death

The effects of a ruptured brain aneurysm usually worsen quickly within minutes—necessitating emergency medical treatment.


Most brain aneurysms do not cause death, because most of them do not rupture. But when a large brain aneurysm does rupture, there is a high chance of death.

The outcome of a ruptured brain aneurysm is worse if the following factors are present:

  • A brain aneurysm was large before it ruptured
  • It causes bleeding and compression in a critical area of the brain, such as the brain stem


Aneurysms can occur in any blood vessel throughout the body, including the brain. An aneurysm is a bulging area in the wall of an artery. Arteries are blood vessels that carry oxygen-rich blood, and they have higher pressure than other blood vessels (such as capillaries and veins). Usually, the outpouching of a brain aneurysm forms in a delicate section of an arterial wall.

Brain aneurysms commonly form in the circle of Willis, a group of blood vessels in the brain.

It is not completely clear why some people develop aneurysms in the brain, and the risk factors are not exactly the same as risk factors for other aneurysms (such as abdominal aortic aneurysms). Brain aneurysms are generally described as idiopathic, which means that they occur without a known cause.

Genetics is believed to play a role in the development and rupture of brain aneurysms, though most people who have them do not have a family history of brain aneurysms. Head trauma may also increase the risk of developing a brain aneurysm.

An aneurysm may cause the arterial wall to rip, tear, or rupture.

Risk Factors for Rupture of a Brain Aneurysm

All brain aneurysms are at risk of bleeding. If you have a brain aneurysm, it is not possible to know which path it will follow over the course of the next few years or over the course of your life.

There are several factors associated with a higher chance of brain aneurysm rupture:

  • Increase in size of the aneurysm
  • Seizures
  • Smoking
  • Untreated hypertension
  • Previous rupture without treatment
  • Alcohol use


When an aneurysm ruptures, bleeding can often be detected with a brain computerized tomography test (CT). Sometimes, brain CT or magnetic resonance imaging (MRI) can be used to visualize the aneurysm. But often, cerebral angiography, a type of brain imaging study that focuses on blood vessels, is needed to locate a brain aneurysm

There are several types of cerebral angiograms, including CT angiography (CTA) and MR angiography (MRA). An interventional cerebral angiogram, which involves placement of a catheter (tube) attached to a camera, can be used as well. This interventional test is considered more accurate than CTA and MRA, but it poses a higher risk of complications.

Follow-Up Imaging

If you have an unruptured brain aneurysm that will be monitored, you will need to have follow-up imaging studies. Your healthcare providers may order a brain MRI, brain MRA, brain CT, brain CTA, or a cerebral angiogram at certain intervals to monitor your aneurysm. The size and location of your brain aneurysm determine which of these is the best imaging technique for you.

You should make every effort to keep your actual brain scan or images of the scans for later comparison (in case you change healthcare providers or hospitals), because the key to follow-up lies in whether the aneurysm changes or grows over time. The pictures, rather than the reports, are typically compared.


The chance that a non-growing brain aneurysm will rupture is about 0.5 % to 1.1 % per year, and a growing brain aneurysm has about a 5% chance of rupturing each year. Over time, unruptured aneurysms tend to be less likely to rupture or bleed.

Several scoring systems  have been proposed to help in predicting the risk of rupture, and the angle of the aneurysm may have some relationship to the risk of rupture as well.

Ruptured brain aneurysms are fatal in about 50% of cases. Of those who survive, about 66% suffer some permanent neurological deficit. Approximately 15% of people with a ruptured aneurysm die before reaching the hospital. Most of these deaths are due to rapid and massive brain injury from the initial bleeding.


The treatment plan for a brain aneurysm is a very individualized, high-level decision that you will make with the advice of your neurologist, your neurosurgeon, and possibly a neuro-interventional radiologist.

Some unruptured aneurysms need to be surgically repaired, while others are not treated. Because the repair of an aneurysm involves major brain surgery, the risk of surgery may be deemed higher than the risk of an aneurysm rupture in some cases. For example, small aneurysms, often described as berry aneurysms, are often not treated.

If your aneurysm will not be repaired, your healthcare providers may advise lifestyle changes to reduce the risk of rupture.

If you experience a brain aneurysm rupture, treatment involves medical management, possible surgical intervention, and rehabilitation.


Brain aneurysm surgery is a particularly delicate surgical procedure, and it requires careful planning. Surgery may be the best way to prevent bleeding from brain aneurysms that are likely to rupture due to their size, location, or another risk factor.

Brain aneurysm surgery involves placing a metal coil or a clip on the aneurysm in order to shrink the out-pouching by diminishing blood flow. Eventually, the aneurysm withers away, and the blood vessel heals, resuming normal blood flow.

Surgery may require an open craniotomy (temporary removal of the skull). Some brain aneurysms can be repaired using a minimally invasive procedure in which an artery is punctured through the skin and a catheter is threaded to the cerebral aneurysm.

Lifestyle Changes

There are some lifestyle factors that can increase the likelihood of brain aneurysm rupture. Head trauma can trigger bleeding of a brain aneurysm, and your healthcare provider may recommend avoiding activities that involve hitting your head.

Extremely high blood pressure, such as that which can be triggered by recreational drugs such as methamphetamine and cocaine, can cause a brain aneurysm to rupture.

Recovery after Brain Aneurysm Rupture

After a brain aneurysm rupture, bleeding in the brain can cause seizures, loss of consciousness, paralysis, vision loss, or difficulty communicating. Other complications may occur, such as heart and blood pressure irregularities and difficulty breathing. Edema (swelling) can occur in the brain as well, causing further brain damage.

Medical treatment can include intravenous (IV) fluids, anti-epilepsy drugs, steroids, blood pressure management, cardiac medications, and/or mechanical assistance with breathing.

Some people have surgery to repair a brain aneurysm after it has ruptured, but this depends on the situation.

Rehabilitation is similar to rehabilitation after a stroke, and can include speech therapy, physical therapy, and cognitive therapy.

A Word From Verywell

A brain aneurysm is not a simple, routine diagnosis—so it might sound scary. However, if you or a loved one has a brain aneurysm, you should know that there are effective treatments and that there are knowledgeable medical teams who are experienced in brain aneurysm care.

No one can predict your prognosis with exact certainty, but there are some factors that make a brain aneurysm rupture more or less likely, including its size and location and your symptoms and overall health. If you are in a high-risk group, or even if you are in a low-risk group, a number of well-studied interventions can significantly reduce your chances of a brain aneurysm rupture.

4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.