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Understanding Brain Aneurysms: Causes, Symptoms, and Treatment Options

Updated: Dec 14, 2023


A brain aneurysm is a bulge in a blood vessel caused by a weakness in the blood vessel wall, most commonly in the place it branches. The medical term for an aneurysm inside the brain is an intracranial or cerebral aneurysm

An aneurysm often looks like a berry on a stem. It develops as blood pressure puts strain on the weakened blood vessel and over time causes a small area to bulge and grow outwards like a balloon.

Most brain aneurysms don't rupture or cause any symptoms or health problems. In case it does rupture, it causes bleeding in the brain, known as a haemorrhagic stroke. Most often, a rupture of a brain aneurysm occurs in the space between the brain and the thin brain membrane called the arachnoid membrane. This type of haemorrhagic stroke is called a subarachnoid haemorrhage.

Brain aneurysms are common. Some experts believe the prevalence could be as high as 1 in 20 people, while others think the number is much lower and affects closer to 1 in 100 people. The number of brain aneurysms that rupture is much smaller and happens approximately 1 in 15,000 people every year.

In many cases, brain aneurysms are found during tests for other conditions (accidental finding). The majority of brain aneurysms aren't dangerous, especially if they are small and unruptured. However, a larger unruptured aneurysm may cause symptoms if it presses on brain tissues and/or intracranial nerves. An unruptured aneurysm may require treatment in some cases to prevent rupture in the future.

Unlike an unruptured aneurysm, a ruptured aneurysm quickly becomes a life-threatening emergency and requires medical treatment right away.

Common symptoms of a ruptured brain aneurysm

  • A sudden agonizing headache, similar to a sudden hit on the head

  • Neck stiffness

  • Nausea and vomiting

  • Light sensitivity (photophobia)

  • Seizure

  • Loss of consciousness

  • Confusion

Types of aneurysms

Saccular aneurysm also known as berry aneurysm. This is the most common type of aneurysm and mostly develops on arteries at the base of the brain.

Fusiform aneurysm - This type of aneurysm causes bulging on all sides of the artery.

Mycotic aneurysm - This type of aneurysm is caused by an infection when an infection affects the arteries in the brain. This can weaken the artery wall and cause an aneurysm to form.

What causes a brain aneurysm

While the exact causes of a weakening of the blood vessel walls leading to aneurysm are still unclear, certain risk factors have been identified.

Risk factors for brain aneurysm

  • Smoking

  • High blood pressure

  • Family history of brain aneurysms


CT scans are usually the first tests used to detect bleeding in the brain (Fig 1).

A CT angiogram can create more detailed images and detect the presence of an aneurysm (Fig 2).

Magnetic resonance imaging (MRI/MRT) can show if there's bleeding in the brain. A type of MRI that captures images of the arteries in detail is called MR angiography (Fig 3).

Lumbar punctures are sometimes used If you have symptoms of a ruptured aneurysm but a CT scan doesn't show evidence of bleeding.

Digital Subtraction Angiography provide a detailed image of the blood vessels in the brain. The procedure involves inserting a catheter into an artery in the groin and passing it up to the blood vessels in the brain (Fig 4)


Brain aneurysms are treated surgically if they have ruptured or there's a risk of rupture. Preventative surgery is usually only recommended if there's a high risk of a rupture. There are two common treatment options for repairing a ruptured brain aneurysm.

Surgical clipping

Clipping is a procedure to close an aneurysm. After removing a part of the skull, the neurosurgeon follows the blood vessel that feeds the aneurysm, finds the aneurysm and places a tiny metal clip on the neck of the aneurysm to stop blood flow into it.

Endovascular treatment

This is a less invasive procedure than surgical clipping. Endovascular treatment involves accessing the aneurysm by passing a catheter through the artery. The catheter is advanced into the brain arteries. Then coils or stents may be placed.


It’s not always possible to prevent brain aneurysms, but one can lower the risk by not smoking and by keeping blood pressure in a normal range.

If you or someone you know is experiencing symptoms mentioned here, seek medical attention immediately.

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