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Brain aneurysm

Overview of brain aneurysm

A brain aneurysm is a ballooning blood vessel located in the brain. If this vessel ruptures, it can cause bleeding into your brain, as well as other potentially serious complications and even death.

Almost half of the people who develop a ruptured brain aneurysm do not survive. Of those who do, more than half experience permanent brain damage.


Most brain aneurysms don’t have any symptoms. However, symptoms can develop if a brain aneurysm grows large or it bursts.

Signs and symptoms of a ruptured aneurysm can include:

  • severe, excruciating headache
  • eye pain
  • vision changes
  • weakness
  • numbness
  • nausea
  • vomiting
  • stiff neck

If you think you or a loved one may have a ruptured aneurysm, call 911 immediately.


The underlying cause of an aneurysm is a defect or weakening at an artery junction point. When artery walls become thin or weak, they may balloon out and fill with blood.

There are many potential causes, including:

  • Medical conditions that affect the circulatory system, such as high blood pressure, polycystic kidney disease, atherosclerosis, and diabetes
  • Previous trauma to the brain
  • Inherited abnormalities
  • Lifestyle factors such as excess alcohol use, tobacco use, and drugs such as cocaine
  • Some rare tumor types and localized infections


Aneurysms can be described based on their shape, size, location, and cause.

For example, there are three primary classifications for brain aneurysms:

  • Saccular aneurysms are the most common and occur when a balloon-shaped sack of blood bulges out of an artery in the brain. Saccular aneurysms typically form on arteries near the base of the brain. They are also sometimes called “berry aneurysms” since their shape resembles grapes on a vine.
  • Fusiform aneurysms bulge out in multiple directions, instead of forming a berry-shaped pocket.
  • Mycotic aneurysms are uncommon and result from a type of infection that affects arteries in the brain.

Aneurysms can also be classified based on how big they are:

  • Small aneurysms are less than 11 mm across (about the size of a pea)
  • Large aneurysms are up to 25 mm across (dime-sized)
  • Giant aneurysms are more than 25 mm across (quarter-sized)

Risk factors

Some people have a higher risk of brain aneurysms than others. Women are at higher risk, and aging also increases the likelihood of developing an aneurysm.  

Your risk is higher if someone in your family had a brain aneurysm as well; some arterial defects are hereditary.


In many cases, an aneurysm is the result of trauma, inherited conditions, or other factors outside your control. However, a healthy lifestyle and avoiding cigarettes, alcohol, and other drugs can help reduce risks.

Maintaining a healthy weight and low blood pressure can also reduce your risk.

It is not typically necessary or recommended to screen for cerebral aneurysms if you do not show symptoms and have no family history, personal history, or other risk factors.

The information contained in this article is meant for educational purposes only and should not replace advice from your healthcare provider.

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