What is a brain aneurysm?

A brain (cerebral) aneurysm is a bulging, weak area in the wall of an artery that supplies blood to the brain. Most brain aneurysms don't cause problems.

Sometimes an aneurysm bursts, or ruptures. Blood may spill into the area between the brain and the skull (subarachnoid hemorrhage). This bleeding in the brain is also called a hemorrhagic stroke. The bleeding may lead to brain damage or even death.

What causes it?

A person may inherit the tendency to form aneurysms, or aneurysms may develop because of hardening of the arteries (atherosclerosis) and aging. Some risk factors that can lead to brain aneurysms can be controlled, and others can't. The following risk factors may increase your risk for an aneurysm or, if you already have an aneurysm, may increase your risk of it rupturing:

• Family history. People who have a family history of brain aneurysms are more likely to have an aneurysm than those who don't. Aneurysms may also be linked to certain inherited diseases.
• Previous aneurysm. People who have had a brain aneurysm are more likely to have another.
• Being biologically female. This raises the risk of developing a brain aneurysm or suffering a subarachnoid hemorrhage.
• High blood pressure. The risk of subarachnoid hemorrhage is greater in people who have a history of high blood pressure.
• Smoking, vaping, or using other tobacco or nicotine products. Tobacco and nicotine use damages arteries and increases the risk that an aneurysm will rupture.
• Drugs or heavy alcohol use. People who use drugs, such as cocaine, or drink a lot of alcohol have a higher risk of a brain aneurysm.
• Connective tissue disorders. These disorders can weaken the artery walls and increase the risk for aneurysms.
• Diabetes. Diabetes increases the risk of atherosclerosis, which increases the risk of fusiform aneurysms.
• Polycystic kidney disease. This disease causes fluid-filled sacs to grow in the kidneys and may increase blood pressure.

What are the symptoms?

Most brain aneurysms don't cause symptoms. But in some cases, an aneurysm may press on areas in the brain. This may cause symptoms such as headaches, vision problems, changes in speech, or neck pain. The symptoms depend on what areas of the brain are affected and how big the aneurysm is.

If a brain aneurysm ruptures, symptoms often come on suddenly. They may include:

• A sudden, severe headache that is different from past headaches.
• Neck pain or stiffness.
• Nausea and vomiting.
• Sensitivity to light.
• Fainting or loss of consciousness.
• Seizures.
• A dilated pupil.
• Pain above and behind the eye.
• Confusion.
• Weakness or numbness.
• Blurred or double vision.
• A drooping eyelid.

How is it diagnosed?

Because unruptured brain aneurysms often do not cause any symptoms, many are discovered in people who are being treated for a different condition.

If your doctor believes that you have a brain aneurysm, you may have the following tests:

• Computed tomography (CT) scan. A CT scan can help identify bleeding in the brain. Sometimes a lumbar puncture may be used if your doctor suspects that you have a ruptured cerebral aneurysm with a subarachnoid hemorrhage.
• Computed tomography angiogram (CTA) scan. CTA is a more precise method of evaluating blood vessels than a standard CT scan. CTA uses a combination of CT scanning, special computer techniques, and contrast material (dye) injected into the blood to produce images of blood vessels.
• Magnetic resonance angiography (MRA). Similar to a CTA, MRA uses a magnetic field and pulses of radio wave energy to provide pictures of blood vessels inside the body. As with CTA and cerebral angiography, a dye is often used during MRA to make blood vessels show up more clearly.
• Cerebral angiogram. During this X-ray test, a catheter is inserted through a blood vessel in the groin or arm and moved up through the vessel into the brain. A dye is then injected into the cerebral artery. As with the above tests, the dye allows any problems in the artery, including aneurysms, to be seen on the X-ray.

How is a brain aneurysm treated?

The treatment options for a brain aneurysm depend on a few things. These things include your age, size and location of the aneurysm, any additional risk factors, and your overall health.

If you have an aneurysm with a low risk of rupture, you and your doctor may want to continue to observe your condition rather than do surgery. You might make this choice because surgery also has risks. Your doctor may suggest ways to keep your blood vessels as healthy as possible, such as managing high blood pressure and not smoking. If your aneurysm is large or causing pain or other symptoms, though, or if you have had a previous ruptured aneurysm, your doctor may recommend surgery.

The following procedures are used to treat both ruptured and unruptured brain aneurysms:

• Endovascular embolization. During this procedure, a small tube is inserted into the affected artery and positioned near the aneurysm. For coil embolization, soft metal coils are then moved through the tube into the aneurysm, filling the aneurysm and making it less likely to rupture. In mesh embolization, mesh is placed in the aneurysm, reducing blood flow to the aneurysm and making it less likely to rupture. These procedures are less invasive than surgery. But they involve risks, including rupture of the aneurysm.
• Surgical clipping. This surgery involves placing a small metal clip around the base of the aneurysm to isolate it from normal blood circulation. This decreases the pressure on the aneurysm and prevents it from rupturing. Whether this surgery can be done depends on the location of the aneurysm, its size, and your general health.

Both of these procedures should be done in a hospital where many procedures like these are done.

Aneurysms that have bled are very serious. In many cases, they lead to death or disability. Management includes hospitalization, intensive care to relieve pressure in the brain and maintain breathing and vital functions (such as blood pressure), and treatment to prevent rebleeding.