Brain aneurysm

A brain aneurysm (or cerebral aneurysm) is a bulge in the wall of an artery in the brain. As blood rushes past a weak spot in the artery wall, it balloons out and forms the aneurysm. Brain aneurysms can occur at any age, but they are more common in adults over 40 than in children. They are also more common in women than in men.

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Symptoms of brain aneurysms

Symptoms will depend on whether or not the aneurysm has ruptured.

Ruptured brain aneurysm

Usually, a ruptured aneurysm occurs between the brain and the thin tissue covering it. This is known as a subarachnoid hemorrhage.

Ruptured aneurysms require immediate medical attention to prevent brain damage or even death. If you have any of the following symptoms, seek immediate medical attention:

  • Blurred or double vision.
  • Brief blackout.
  • Clumsiness.
  • Coma.
  • Confusion.
  • Dilated pupils.
  • Jerking movements, such as seizures or convulsions.
  • Nausea and vomiting.
  • Pain behind the eyes.
  • Paralysis or weakness on one side of the body.
  • Severe headache, usually of very sudden onset.
  • Slow movements.
  • Speech problems.
  • Stiff neck.

Unruptured brain aneurysm

A brain aneurysm may not rupture, especially if it is a small aneurysm. You could live a happy, healthy life without ever knowing you have an aneurysm. Sometimes, you may be diagnosed with a brain aneurysm during routine medical tests. In this case, it is best to talk to your doctor about whether treatment is appropriate.

Sometimes, however, unruptured aneurysms may grow and press on your brain tissue. This can lead to:

  • A dilated pupil.
  • Facial numbness.
  • Pain above and behind your eyes.
  • Vision changes, like double vision.

“Leaking” aneurysms

An aneurysm may also leak small amounts of blood without rupturing entirely (sentinel bleed). This bleeding can damage brain tissue and increase pressure on the brain.

The primary symptom of a ‘leaking’ aneurysm is often a sudden, severe headache.

Generally, leaking is followed by a more severe rupture, so seek medical attention immediately if you are experiencing symptoms.

Brain aneurysm diagnosis

If you are presenting with symptoms of a brain aneurysm, your doctor will perform a series of tests to determine if you have a subarachnoid hemorrhage or another type of stroke. These tests include:

  • CT (computed tomography) scan. A CT scan is a detailed, cross-sectional image of your brain. Your doctor will examine these images to see if there is bleeding.
  • MRI (magnetic resonance imaging) scans. An MRI uses strong magnets and radio waves to create a detailed image of the brain and blood vessels.
  • Cerebrospinal fluid test. If you have had a subarachnoid hemorrhage, there may be red blood cells present in your cerebrospinal fluid. Your doctor can take a sample of this fluid and test for the presence of blood cells if the aneurysm can’t be detected on a CT scan or MRI.
  • Cerebral angiography. For this imaging technique, your doctor will insert a thin tube (a catheter) into a large artery in your leg or groin. He or she will carefully guide the tube to the blood vessels in your neck, at which point they will inject a special contrast dye. A series of x-rays will then be taken, and the dye will help create a detailed map of your arteries so that your doctor can pinpoint the aneurysm. This is an invasive procedure, so doctors usually use it only after other imaging techniques have proven inadequate.

Risk factors for brain aneurysms

A range of factors may increase your risk of developing an aneurysm. These include:

Brain aneurysm complications

A ruptured aneurysm may be associated with other complications, such as:

  • Cerebral vasospasm. After an aneurysm rupture, your brain’s blood vessels may rapidly constrict, cutting off blood flow to brain cells and resulting in further damage.
  • Hydrocephalus. A ruptured aneurysm may cause a subarachnoid hemorrhage (see above). This leads to bleeding in the space between your brain and surrounding tissue, which disrupts the circulation of the cerebrospinal fluid surrounding your brain and spinal cord. The result is increased pressure on the brain and more damage.
  • Hyponatremia. Bleeding in the brain can disrupt the amount of sodium in your blood and lead to swelling.
  • Re-bleeding. A ruptured aneurysm may start bleeding again, leading to further tissue damage.

All of these complications can lead to permanent brain damage. Getting immediate medical attention is essential for avoiding these complications.

Brain aneurysm treatment

Treatment for a brain aneurysm needs to start right away for the best chance of success. Your doctor will determine the best treatment based on the type, size and location of the aneurysm, as well as if it has ruptured. Treatments for ruptured aneurysms include:


Surgical clipping. This procedure closes off the aneurysm and prevents further bleeding. Your surgeon will remove a section of your skull to access the aneurysm. He or she will then place a tiny metal clip on the aneurysm to stop blood flow to it.

Endovascular coiling (or endovascular embolization). This procedure is less invasive than surgical clipping. Your doctor will insert a thin tube (a catheter) into a large artery in your leg or groin. He or she will carefully guide the tube through your body and into your brain. Then, your doctor will push a small wire through the catheter. This wire will coil up inside the aneurysm, stopping blood flow. While it is initially safer, endovascular coiling carries a higher risk of re-bleeding.

Flow diverters. Flow diverters are a newer treatment for aneurysms and are suitable for larger aneurysms. A small, tubular stent is implanted into your artery, diverting blood flow away from the aneurysm and stimulating your body to heal.

Additional interventions

Other interventions may be used following a ruptured aneurysm to reduce the risk of complications and improve your long-term outcomes. These include:

  • Anti-seizure medication. Sometimes, a ruptured aneurysm can cause seizures. Anti-seizure medications help prevent other seizures and avoid additional brain damage.
  • Calcium channel blocker medication. This prevents calcium from entering the walls of the blood vessels. This lessens the chance for vasospasm, one of the complications of a ruptured aneurysm.
  • Pain relievers. To reduce the headache pain associated with a ruptured aneurysm.
  • Rehabilitation. Damage to the brain from a ruptured or leaking aneurysm may affect your ability to carry out daily tasks. Physical, speech and occupational therapy may be needed to relearn essential skills.
  • Ventricular or lumbar drainage catheters. These lessen the pressure on your brain and help prevent hydrocephalus by draining off excess cerebrospinal fluid into an external bag.

If you are diagnosed with an unruptured aneurysm, you may still need treatment to prevent a future rupture. Talk to your doctor about whether certain preventative treatments are appropriate for you.


National Institute of Neurological Disorders and Stroke (NINDS). Cerebral Aneurysms Fact Sheet (

American Heart Association (AHA). What You Should Know About Cerebral Aneurysms (

American Association of Neurological Surgeons (AANS). Cerebral Aneurysm (