Brain (cerebral) aneurysm

Neurosurgeons from UW Medicine offer expert care for ruptured and unruptured brain (cerebral) aneurysms.

Brain (cerebral) aneurysm

Neurosurgeons from UW Medicine offer expert care for ruptured and unruptured brain (cerebral) aneurysms.

Key points about brain (cerebral) aneurysms

  • A brain aneurysm is a bulging, weak area in the wall of an artery in the brain. The area balloons out. 
  • The weak, bulging spot is at risk for tearing (rupture). 
  • Seek immediate medical attention or call 911 if you have some or all of the symptoms listed above. 
  • Treatment options may include surgical clipping or endovascular coiling.

Unruptured brain aneurysms can be treated

What is a brain (cerebral) aneurysm?

A brain aneurysm is a bulge in a weak area of the wall of a brain artery. It puffs out like a small balloon and fills with blood. It is also called an intracranial aneurysm or brain aneurysm. This bulge makes the artery more likely to tear (rupture) in that spot. 

A brain aneurysm occurs more often in arteries at the base of the brain. But it may occur in arteries anywhere in the brain. 

A normal artery wall is made up of 3 layers. The wall where the aneurysm forms is thin and weak. The weak area is caused by too little muscle in the artery wall. There are several types of aneurysms. They are: 
 

  • Berry (saccular) aneurysm. This type is the most common. It is typically found in arteries at the base of the brain. It looks like a berry with a narrow stem. More than 1 of these may occur at the same time. 

  • Fusiform aneurysm. This type bulges out on all sides. This forms a dilated artery. This type is often linked to atherosclerosis. 

  • Dissecting aneurysm. This type is caused by a tear along the length of the artery in the inner layer of the artery wall. Blood leaks in between the layers of the wall. It may cause 1 side of the artery wall to balloon out. Or it may block blood flow through the artery. This type of aneurysm usually happens from a traumatic injury. But it can also happen all of a sudden from an unknown cause. 

  • Mycotic aneurysm. If bacteria spread in the blood, an infection may develop in the artery wall. This weakens the wall of the artery, causing a bulging aneurysm to form. More than 1 of these often occur at the same time. They are at higher risk of bleeding and serious complications than other types. This type is less common. 

Most small brain aneurysms don't cause symptoms. They are less than 0.4 inches (10 millimeters) across. Smaller aneurysms may be less likely to break. 

Stethascope

Living with an unruptured aneurysm?

What are the symptoms of brain aneurysms?

You may not know you have a brain aneurysm until it tears (ruptures). Most brain aneurysms have no symptoms and are small in size. Smaller aneurysms may have a lower risk for rupture. 

In some cases, symptoms may happen before a rupture. They may occur because of blood that leaks. This is called a sentinel hemorrhage around the brain. Some aneurysms also cause symptoms because they press on nearby structures. These can include nerves to the eye. They can cause vision loss or make it harder to move your eye even if the aneurysm has not ruptured. 

The symptoms of a brain aneurysm that has not ruptured include: 
 

  • Headaches (very rare, if there is no rupture) 
  • Eye pain 
  • Vision changes 
  • Less able to move the eye 

The first sign of a bleeding brain aneurysm is most often bleeding around the brain. This is called a subarachnoid hemorrhage (SAH). This may cause symptoms such as: 
 

  • Sudden, very severe headache 
  • Stiff neck 
  • Nausea and vomiting 
  • Changes in mental status, such as drowsiness 
  • Pain in specific areas, such as the eyes 
  • Dilated pupils 
  • Loss of consciousness 
  • High blood pressure 
  • Loss of balance or coordination 
  • Sensitivity to light 
  • Back or leg pain 
  • Problems with some functions of the eyes, nose, tongue, or ears 
  • Coma and death 

The symptoms of a brain aneurysm may be like those of other health problems. It is important to seek immediate medical treatment for a diagnosis. 

When should I contact my doctor?

Call 911 immediately if you: 

  • Develop a sudden, severe headache — especially if it feels like the worst headache of your life 
  • Experience nausea or vomiting 
  • Feel confused 
  • Have a seizure 
  • Lose consciousness 

These are common signs of a ruptured brain aneurysm. Call 911 or ask a loved one to drive you to the nearest emergency room. 

Call your doctor if you: 

  • Have blurred or double vision 
  • Have a dilated pupil in just one eye 
  • Feel pain around or behind one eye 
  • Have numbness or weakness on one side of the face 

These may be signs of an unruptured aneurysm that has grown large enough to press against a nerve or brain tissue.
 

How to make an appointment

Call 911 immediately if you are experiencing symptoms of a ruptured brain aneurysm. In one of our emergency departments, the emergency care team and neurovascular experts will diagnose the aneurysm and decide on an appropriate course of action.  

If you have been previously diagnosed with an aneurysm and are not experiencing emergency symptoms, request a consultation with the UW Medicine brain aneurysm team.  

If you have questions or concerns, call your primary care doctor.

Brain aneurysm care at UW Medicine

Thanks to modern imaging and surgical procedures, it’s easier than ever to diagnose and treat brain aneurysms. You’ll find these procedures — and more — at UW Medicine. Our neurosurgeons offer planned procedures for people whose unruptured aneurysm should be treated. They also perform lifesaving emergency treatments to repair ruptured aneurysms. 

Whether your aneurysm surgery is sudden or scheduled, you can have confidence in our team’s experience and expertise. We offer advanced endovascular treatments, including aneurysm coiling and flow diverter stent placement, that let us treat aneurysms less invasively. And we can also perform aneurysm clipping in cases where open brain surgery is the best treatment option.

Our team also provides watchful waiting for people with small, unruptured brain aneurysms. If you have concerns about living with an unruptured brain aneurysm, don’t hesitate to contact us. We’ll help you understand the risks and benefits of keeping track of your aneurysm versus treating it. We’ll teach you what to do if you develop symptoms of a growing or ruptured aneurysm. We’ll help give you peace of mind, so you don’t have to live in fear.

UW Medicine doctors specializing in brain aneurysms

What causes brain aneurysms?

Researchers don't fully know what causes brain aneurysms. They are linked to several things. These include: 

  • Advanced age 
  • Smoking 
  • High blood pressure 
  • Binge alcohol drinking 
  • Being a woman 
  • Family history of aneurysms 
  • Polycystic kidney disease 

The main cause of a brain aneurysm is a weakening in the wall of an artery. The pressure of the blood being pumped through the artery can then cause the bulge in that weak area. In certain areas, an aneurysm may have more pressure on it. For example, a place where the artery divides into smaller branches may have more pressure.

Who is at risk for a brain aneurysm?

You are more at risk for an aneurysm if you have 1 of the inherited problems below:

  • Alpha-glucosidase deficiency. This is a complete or partial lack of the enzyme needed to break down glycogen and to convert it into glucose. 
  • Alpha 1-antitrypsin deficiency. This is a disease that may lead to hepatitis and cirrhosis of the liver or emphysema of the lungs. 
  • Arteriovenous malformation (AVM). This is an abnormal tangle of blood vessels connecting arteries and veins. 
  • Coarctation of the aorta. This is a narrowing or constriction in a portion of the aorta. The aorta is the main artery coming from the heart. 
  • Ehlers-Danlos syndrome. This is a connective tissue disorder that causes fragile blood vessels. 
  • Fibromuscular dysplasia. This is an artery disease that most often affects the medium and large arteries of young to middle-aged women. 
  • Hereditary hemorrhagic telangiectasia. This is a disorder of the blood vessels. The blood vessels lack capillaries between an artery and vein. 
  • Klinefelter syndrome. This is a condition in men in which they have an extra X chromosome. 
  • Noonan's syndrome. This is a disorder that causes abnormal development of many parts and systems of the body. 
  • Polycystic kidney disease (PCKD). This is a disorder that causes many fluid-filled cysts in the kidneys. PCKD is the most common disease linked to berry aneurysms. 
  • Neurocutaneous syndromes. These include neurofibromatosis or tuberous sclerosis. This is a type of neurocutaneous syndrome that can cause tumors to grow inside the brain, spinal cord, organs, skin, and bones. 

Other risk factors linked to aneurysms may include: 

  • Advanced age 
  • Being a woman 
  • Alcohol drinking, especially binge drinking 
  • Atherosclerosis, which is a buildup of plaque in the inner lining of an artery 
  • Cigarette smoking 
  • Using illegal drugs such as cocaine or methamphetamine 
  • High blood pressure 
  • Head injury 
  • Infection 

These risk factors increase a person's risk. But they don't necessarily cause the disease. Some people with 1 or more risk factors never develop the disease, while others develop the disease and have no known risk factors. Knowing your risk factors to any disease can help to guide you to change behaviors and be checked for the disease.

How is a brain aneurysm diagnosed?

A brain aneurysm is often found after it has ruptured. It may be found by chance during an imaging test for other reasons. Your healthcare provider will ask about your health history and do a physical exam. You may also need tests such as:

  • Cerebral angiography. This test makes an image of the blood vessels in the brain. It can find a problem with vessels and blood flow. The procedure is done by putting a thin tube (catheter) into an artery in the leg. The tube is passed up to the blood vessels in the brain. Contrast dye is injected through the catheter. X-ray images are taken of the blood vessels. 
  • CT scan. This test uses X-rays and a computer to make detailed images of the body. A CT scan shows details of the bones, muscles, fat, and organs. CT scans are more detailed than general X-rays. It may be used to help show the location of the aneurysm and if it has burst or is leaking. A CT angiogram (CTA) can also be done with a CT scan to look at the blood vessels. 
  • MRI. This test uses large magnets, radio waves, and a computer to make detailed images of organs and tissues in the body. An MRI uses magnetic fields to see small changes in brain tissue. It can help to find and diagnose an aneurysm. 
  • Magnetic resonance angiography. This noninvasive test uses an MRI and IV (intravenous) contrast dye to show blood vessels. Contrast dye causes blood vessels to look opaque on the MRI image. This lets the healthcare provider see the blood vessels more clearly. 

How is a brain aneurysm treated?

The main goal is to decrease the risk of bleeding in the brain. 

Many factors are considered when making treatment choices. These include: 
 

  • The size and location of the aneurysm 
  • If you have symptoms 
  • Your age and overall health 
  • If you have risk factors for aneurysm rupture 
  • In some cases, the aneurysm may not be treated. You may instead be closely watched by a healthcare provider over time. In other cases, surgery may be needed. 

There are 2 main types of surgery for a brain aneurysm. They are: 

  • Open craniotomy (surgical clipping). This procedure is done by removing part of the skull to reach the aneurysm. The surgeon places a metal clip across the neck of the aneurysm. This is done to prevent blood flow into the aneurysm bulge. Once the clipping is done, the skull is closed back together. 
  • Endovascular coiling. This is also called coil embolization. It is a minimally invasive method. It is the most common method used to treat brain aneurysms. An incision in the skull is not needed. Instead, a catheter is pushed up from a blood vessel in the groin into the blood vessels in the brain. Fluoroscopy (live X-ray) is used to help move the catheter into the head and into the aneurysm. Once the catheter is in place, tiny platinum coils are put through the catheter into the aneurysm. These soft coils are visible on an X-ray. They conform to the shape of the aneurysm. The coiled aneurysm becomes clotted off (embolization). That removes blood flow to the aneurysm to prevent rupture. This procedure is done with general anesthesia, sedation, or local anesthesia.

What are possible complications of a brain aneurysm?

  • Bleeding. Bleeding is usually around the brain. An aneurysm can also bleed in the brain and in the cerebral ventricles. 
  • Rebleeding. The second bleed is often worse than the first. Because of this, early treatment is vital after the first bleed. 
  • Vasospasm. This is narrowing of the cerebral arteries. It usually occurs 3 to 14 days after an aneurysm has bled. It can lead to strokes and death. This problem happens in up to half of people who had an aneurysm bleed, even if the bleed was treated. 
  • Hydrocephalus. This is fluid buildup on the brain. It is caused by cerebrospinal fluid (CSF) that is not reabsorbed normally. 
  • Compression of the brain or cranial nerves. This can lead to some nervous system problems. These can include eye movement paralysis. 
  • Reoccurrence. Some aneurysms can happen again after being treated. 

What can I do to prevent a brain aneurysm?

Controlling your risk factors may lower your risk of having an aneurysm. These risk factors include: 

  • Drinking alcohol (especially binge drinking) 
  • Atherosclerosis 
  • Obesity 
  • Cigarette smoking 
  • Use of illegal drugs, such as cocaine or amphetamine 
  • High blood pressure 
  • Head injury 
  • Infection

Talk with your healthcare provider about lowering your risk for a brain aneurysm.