A brain aneurysm is a deformity of an artery where a spot in the arterial wall in the brain bulges and fills with blood. It may also be called an intracranial aneurysm or cerebral aneurysm.

an illustration of a brain aneurysmShare on Pinterest
Illustration by Sophia Smith

A brain aneurysm is a potentially life threatening condition that can affect a person at any age. If a brain aneurysm bursts, or ruptures, it’s an emergency situation that can result in a stroke, brain damage, and even death if not treated immediately.

Below, we’ll explore more about brain aneurysms, including their symptoms, causes, and potential treatment options.

Brain aneurysms are unpredictable and may not show any symptoms until they grow large or rupture. Large or ruptured aneurysms will usually show definite symptoms and require emergency medical care.

The symptoms and warning signs of a brain aneurysm vary based on whether it has ruptured or not.

Unruptured aneurysms

Small aneurysms don’t typically cause any noticeable signs. However, an aneurysm that becomes large may start to press on surrounding nerves and tissues, leading to symptoms.

It’s estimated that only 10 to 15 percent of unruptured aneurysms cause symptoms. When present, the symptoms of an unruptured brain aneurysm can include:

Contact your doctor as soon as possible if you experience any of these symptoms.

Leaking aneurysms

It’s possible for an aneurysm to leak and release a small amount of blood into the brain. If you have a brain aneurysm that’s leaking, you may experience a sudden, severe headache. This is called a sentinel headache.

Sentinel headaches may develop in the days or weeks before a brain aneurysm completely ruptures. If you experience a sudden, severe headache, particularly if it occurs with other aneurysm symptoms, seek immediate medical care.

Ruptured aneurysms

The symptoms of a ruptured brain aneurysm can include:

A ruptured aneurysm is life threatening. Seek emergency medical attention right away if you experience one or more of these symptoms.

Brain aneurysms happen due to structural changes in the walls of an artery in the brain. These changes cause the walls of the artery to get weaker and become thin. The deformity can happen due to thinning of the wall, but sometimes inflammation or trauma can cause the deformity without thinning.

It’s still unclear what exactly causes aneurysms to form. However, it’s believed that one or a combination of the following factors may promote their development:

  • a break down of elastic tissue within the artery
  • stress from blood flow through the artery
  • tissue changes in the artery due to increases in inflammation

Brain aneurysms are also more likely to happen where an artery branches into different directions. This is because arteries are naturally weaker at these locations.

It’s possible for aneurysms to be present from birth. However, they most often develop over the course of your lifetime. This can be due to a variety of risk factors that we’ll discuss below.

Brain aneurysms can take several forms. About 90 percent are saccular, or “berry,” aneurysms. This type forms a sac outside the artery that looks like a berry attached to a vine.

A fusiform aneurysm is a rarer type of aneurysm that affects a longer section of the artery wall, causing the artery to bulge all the way around. It’s estimated that 3 to 13 percent of brain aneurysms are fusiform.

Brain aneurysms can affect anyone. However, some factors can increase your risk.

There are different risk factors for aneurysm development and rupture.

Risk factors for aneurysm formation

There are several risk factors that can increase your risk of developing a brain aneurysm. These include:

  • Age. Most aneurysms are diagnosed in individuals who are over the age of 40.
  • Sex. Women are more likely to get aneurysms than men.
  • Family history. If aneurysms run in your immediate family, your risk of having one is higher.
  • High blood pressure. Untreated high blood pressure, or hypertension, can place additional pressure on the walls of your arteries.
  • Smoking. Smoking can increase your blood pressure and cause damage to the blood vessel walls.
  • Alcohol and drug misuse. Alcohol and drug misuse, specifically cocaine or amphetamine use, can increase blood pressure and lead to inflammation in your arteries.
  • Head injury. In rare cases, a severe head injury can damage blood vessels in your brain, leading to the formation of an aneurysm.
  • Genetic conditions. Certain genetic conditions can damage arteries or impact their structure, increasing the risk of an aneurysm. Some examples include:
  • Congenital conditions. It’s possible that weaknesses in blood vessels can be present from birth. Additionally, congenital conditions like arteriovenous malformations or narrowing of the aorta, called coarctation, can also raise the risk of aneurysms.
  • Infections. Some types of infections can damage artery walls and increase aneurysm risk. These are called mycotic aneurysms.

Risk factors for aneurysm rupture

Some aneurysms will never rupture. However, there are also risk factors that can increase the chance of a ruptured aneurysm.

Some risk factors for rupture are associated with the characteristics of the aneurysm itself. Risk of rupture is raised in brain aneurysms that are:

  • large
  • have grown larger over time
  • located in certain arteries, specifically the posterior communicating arteries and the anterior communicating arteries

Individual factors that increase the risk of rupture include:

  • having a personal or family history of ruptured aneurysms
  • having high blood pressure
  • smoking cigarettes

Additionally, some events may encourage an aneurysm to rupture. An older 2011 study assessed the relative risk of certain events in 250 individuals who had previously experienced a ruptured aneurysm. It found that the following were associated with the rupture of an existing aneurysm:

  • excessive exercise
  • coffee or soda consumption
  • straining during bowel movements
  • nose blowing
  • experiencing intense anger
  • being startled
  • sexual intercourse

Unless an aneurysm ruptures, it may be difficult to diagnose. Doctors can use certain tests to locate brain aneurysms in people who have a family history of the condition, risk factors, and inherited aneurysm-related health issues.

It’s also possible for an aneurysm to be detected during tests for unrelated health conditions, such as headaches or seizures.

Diagnosis of brain aneurysms relies on imaging that can visualize brain tissues and arteries, which may detect the presence of an aneurysm.

Imaging tests may include one or more of the following:

Magnetic resonance imaging (MRI)

An MRI scan works by using radio waves and magnetic fields to create images of your brain. It’s particularly useful for detecting and evaluating unruptured aneurysms.

A type of MRI called magnetic resonance angiography can make detailed images of brain arteries to help pinpoint the location, size, and shape of an aneurysm.

Computed tomography (CT)

A CT scan takes several X-rays to produce horizonal images of the brain. Images from a CT scan are often utilized to find bleeding in your brain due to a leaking or ruptured aneurysm.

A type of CT scan called CT angiography uses a special dye to help your doctor more effectively see how blood is flowing in the arteries of your brain.

Digital subtraction angiography (DSA)

With DSA, a thin, flexible tube called a catheter is inserted into an artery in the groin. The catheter is then threaded up to the brain.

Once in the brain, a special dye is released through the catheter. A computer then uses X-ray images from before and after the application of the dye to produce images. These images include only blood vessels and none of the other surrounding structures, such as bone.

Cerebrospinal fluid (CSF) tests

Sometimes, imaging may not clearly show bleeding due to an aneurysm. In this situation, your doctor may order a test of your CSF, which is collected using a lumbar puncture. The presence of blood in a CSF sample can indicate bleeding in the brain.

A lumbar puncture can be risky for some people because it can lead to brain herniation due to changes in spinal fluid pressure. This test may be done with caution during an evaluation for a brain aneurysm, but sometimes it’s not recommended in these situations.

Treatment for a brain aneurysm can vary based on several factors, including:

  • the location and size of the aneurysm
  • your age and overall health
  • your personal and family medical history
  • whether the aneurysm is at risk of rupturing or has already ruptured

It’s possible that small, unruptured aneurysms that don’t have any risk factors associated with rupture won’t require immediate treatment. Instead, your doctor may recommend periodically monitoring the aneurysm using imaging technology to detect any changes.

When treatment is necessary, it can involve both surgical and lifestyle approaches, which we’ll explain in more detail below.


If the brain aneurysm is accessible, surgery can repair or cut off blood flow to the aneurysm. This can prevent growth, rupture, or recurrence.

Surgical clipping is a type of procedure in which the blood flow to an aneurysm is cut off using a tiny metal clip. This seals off the aneurysm, preventing further growth or rupture. Surgical clipping requires open brain surgery and is performed under general anesthesia.

Endovascular coiling is another surgical procedure used for aneurysms. It’s less invasive than surgical clipping.

During endovascular coiling, a catheter is inserted into an artery in your groin and threaded to your aneurysm. The catheter then releases tiny coils of wire into the aneurysm, helping to block blood flow.

Brain aneurysms treated using this method can sometimes recur, so endovascular coiling may need to be performed more than once.

Flow diverters

Another newer option for treating a brain aneurysm is the placement of a flow diverter. These devices are similar to the stents that are used for artery blockages in the heart.

Flow diverters can be used when an aneurysm is large or cannot be treated using the surgical techniques discussed above. Like endovascular coiling, placing a flow diverter is less invasive than procedures like surgical clipping.

To place a flow diverter, your doctor will first insert a catheter into an artery in your groin, threading it to the area of the aneurysm. When the catheter is in place, the flow diverter is positioned into the artery in which the aneurysm formed.

Once in place, the flow diverter works to redirect blood away from the aneurysm. This helps to prevent it from growing or rupturing.

Flow diverters are generally safe and effective for treating brain aneurysms.

A 2013 clinical trial of 106 large or giant aneurysms found that flow diversion completely blocked blood flow to the aneurysm in 73.6 percent of cases.

A 2019 meta-analysis of flow diverters in 2,614 people with small or medium aneurysms observed complete diversion of blood flow in 74.9 percent of cases.

Lifestyle changes

Making certain lifestyle changes may help you manage aneurysms and prevent them from rupturing. These changes include:

A ruptured brain aneurysm can lead to a hemorrhagic stroke. This happens when blood leaks into the brain itself or into the area between the skull and brain (subarachnoid space).

Bleeding from a ruptured aneurysm can lead to several life threatening complications. If left untreated, they can cause brain damage and coma. Death can occur in some cases.

The potential complications of a ruptured brain aneurysm include:

  • Seizures. Seizures can happen during or shortly after an aneurysm ruptures.
  • Vasospasm. This occurs when your brain’s blood vessels suddenly become narrow, cutting off blood flow to parts of the brain. The risk of vasospasm is highest within 24 hours of an aneurysm rupture.
  • Hydrocephalus. This happens when CSF circulation is impaired and accumulates in the brain, leading to swelling. Hydrocephalus can occur within days of a ruptured brain aneurysm and can also be a long-term complication of a ruptured brain aneurysm, sometimes requiring the placement of a shunt.

Additionally, after a brain aneurysm ruptures, it can rupture again at any time, even after treatment.

Not all aneurysms will rupture. According to the Brain Aneurysm Foundation, about 6.5 million people in the United States have brain aneurysms that haven’t ruptured. In fact, an estimated 50 to 80 percent of all brain aneurysms never rupture in a person’s lifetime.

According to the National Institute of Neurological Disorders and Stroke, about 30,000 individuals in the United States experience ruptured aneurysms each year. When a brain aneurysm ruptures, the outlook is poor, with about 50 percent of individuals dying within 3 months.

Because of this, it’s important to be vigilant in monitoring existing aneurysms as well as taking steps to prevent them from rupturing. It’s possible that your doctor may recommend surgical treatment for aneurysms that are large or at an increased risk of rupturing.

If you notice signs of rupture, it’s vital to seek immediate medical care to increase your chance of survival and recovery.

After a rupture, recovery can take weeks to months, and it’s likely that you’ll need physical, occupational, or speech therapy during this time. It’s also possible that you may never fully recover, depending on the severity of the damage.

A brain aneurysm occurs when the wall of an artery in the brain becomes deformed, usually due to weakness or thinning. This can cause the arterial wall to bulge out and fill with blood. If an aneurysm ruptures, it can lead to life threatening bleeding in the brain.

It’s important to pay attention to the warning signs of a brain aneurysm, particularly if you have any risk factors. If you’re having concerning symptoms that are consistent with a brain aneurysm, contact your doctor immediately.

In some cases, an unruptured brain aneurysm may be managed through monitoring and lifestyle changes. However, larger unruptured brain aneurysms or those at a high risk of rupturing need to be addressed as soon as possible once they’re discovered.

Leaking or ruptured brain aneurysms are a medical emergency and require critical care management from experienced physicians in order to ensure the best possible outcome.