A brain aneurysm is a weak spot in a blood vessel inside your brain that balloons outward

A brain aneurysm is a bulge or ballooning in the wall of an artery inside your brain. The artery wall becomes thin and weak at that spot, the way a balloon stretches when you blow air into it. Most brain aneurysms don't cause symptoms and never rupture — people live their whole lives without knowing they have one. But if the weakened wall tears open, blood spills into the space around your brain, which is a medical emergency.

The bulge itself is usually small — often the size of a grain of rice or a pea. It can stay the same size for years, grow slowly, or grow quickly. Doctors can't predict which aneurysms will rupture and which won't, so finding one raises real questions about what to do next.

Key Takeaways

  • Most brain aneurysms cause no symptoms and are found by accident during imaging for another reason.
  • A ruptured aneurysm causes sudden, severe headache, stiff neck, nausea, vision changes, or loss of consciousness — call 911 immediately if these occur.
  • Doctors use CT scans, MRI, or angiography to find aneurysms and measure their size and location.
  • Treatment options include monitoring with regular imaging, surgical clipping, or endovascular coiling, depending on the aneurysm's size, location, and your age and health.
  • Risk factors include high blood pressure, smoking, family history, and certain genetic conditions, though aneurysms can occur in people with no risk factors.

How a brain aneurysm forms

Blood vessels in your brain are under constant pressure from blood flowing through them. Over time, that pressure can weaken the artery wall at certain spots. The wall thins, loses its normal structure, and begins to bulge outward. Exactly why this happens to some people and not others isn't fully understood, but certain factors make it more likely.

High blood pressure is the strongest known risk factor — it puts extra stress on artery walls. Smoking damages blood vessel walls and makes them weaker. A family history of aneurysms means your relatives have had them, which suggests a genetic component. Some people are born with connective tissue disorders — conditions that affect how their body builds and maintains tissue — that increase aneurysm risk. Certain genetic syndromes like polycystic kidney disease also raise the odds. Age matters too: aneurysms are more common as you get older, though they can happen at any age.

Symptoms you might notice — or might not

An unruptured aneurysm usually causes no symptoms at all. You could have one and never know it. Some people have a large unruptured aneurysm that presses on nearby brain tissue or nerves, which can cause a headache in one spot, vision problems, facial pain, or weakness on one side of the face. But these symptoms are uncommon and easy to mistake for other conditions.

A ruptured aneurysm is different. The sudden bleeding causes immediate, severe symptoms. The headache is often described as "the worst headache of my life" — sudden, intense, and unlike any previous headache. Other signs include a stiff neck, nausea or vomiting, sensitivity to light, vision changes, loss of consciousness, or seizures. If you or someone near you has these symptoms, call 911 right away. A ruptured aneurysm is life-threatening and requires emergency care.

How doctors find and measure an aneurysm

Most brain aneurysms are found by accident. Someone gets a CT scan or MRI for a headache, a head injury, or another reason, and the imaging shows a bulge in an artery. Sometimes a family member has had an aneurysm, and a doctor recommends screening for relatives. Rarely, an aneurysm is found during surgery for another brain condition.

Once an aneurysm is suspected, doctors use more detailed imaging to confirm it and measure its size and exact location. A CT angiogram uses a CT scanner and injected dye to show blood vessels clearly. An MR angiogram does the same thing with an MRI machine. A cerebral angiogram is more invasive: a thin catheter is threaded through an artery in your groin up to the brain, and dye is injected so X-ray images show the aneurysm in detail. This test carries a small risk but gives the clearest picture and is often done before treatment.

Treatment options depend on size, location, and your health

Not every aneurysm needs immediate treatment. A small, unruptured aneurysm in a location that's hard to reach surgically might be monitored instead. You would have repeat imaging — usually an MRI or CT scan — every 6 to 12 months to watch for growth. If the aneurysm stays stable, monitoring may continue indefinitely. If it grows, your doctor will discuss treatment.

When treatment is needed or chosen, two main options exist. Surgical clipping involves opening the skull, locating the aneurysm, and placing a small metal clip across its neck to stop blood flow into the bulge. Endovascular coiling is less invasive: a catheter is guided to the aneurysm, and soft platinum coils are pushed through it to fill the bulge and block blood flow. Coiling can sometimes be done with a stent — a tiny mesh tube that holds the coils in place. Your doctor will recommend one approach based on the aneurysm's size, shape, location, your age, overall health, and whether it has ruptured.

What happens after a ruptured aneurysm

If your aneurysm ruptures, you'll be admitted to an intensive care unit. The first goal is to stop the bleeding and prevent it from happening again. This usually means urgent surgery or coiling — often within 24 to 48 hours. You'll be monitored closely for complications like rebleeding, vasospasm (when blood vessels tighten and reduce blood flow), increased pressure inside the skull, or seizures.

Recovery from a ruptured aneurysm is unpredictable. Some people recover well with minimal lasting effects. Others have permanent brain damage, disability, or cognitive changes. Rehabilitation — physical therapy, speech therapy, occupational therapy — may be needed. The first few weeks are critical, and the hospital stay can last weeks to months. Long-term follow-up with a neurologist is standard.

Living with an unruptured aneurysm

If you've been told you have an unruptured aneurysm, the uncertainty can be stressful. You might worry about rupture, or feel anxious about whether to pursue treatment. These feelings are normal. It helps to understand that most unruptured aneurysms never rupture, and your doctor can give you specific information about your aneurysm's size, location, and growth pattern — all of which affect your personal risk.

Managing risk factors is important. If you have high blood pressure, work with your doctor to control it. If you smoke, quitting reduces your risk. Avoid sudden straining — heavy lifting, intense exercise, or straining during bowel movements — as these can raise pressure inside your head. Some doctors recommend avoiding certain medications or activities, depending on your aneurysm. Ask your doctor what precautions make sense for you. Regular follow-up imaging and check-ins with your neurologist help track any changes.

Frequently Asked Questions

Can stress or exercise cause an aneurysm to rupture?

Sudden increases in blood pressure from stress, heavy lifting, or intense exercise can theoretically trigger rupture, but most ruptures happen without an obvious trigger. People with unruptured aneurysms can usually exercise and live normally, though your doctor may recommend avoiding heavy lifting or straining. Ask what activities are safe for your specific situation.

If my parent had an aneurysm, will I get one?

Having a family member with an aneurysm increases your risk, but it doesn't mean you will definitely have one. Your doctor may recommend screening with imaging if you have a strong family history. Controlling high blood pressure and not smoking also lower your risk.

What's the difference between an aneurysm and a stroke?

A stroke happens when blood flow to the brain is blocked, usually by a clot. A ruptured aneurysm causes bleeding into the brain. Both are emergencies, but the causes and treatments are different. A ruptured aneurysm is sometimes called a hemorrhagic stroke because bleeding is involved.

How often should I have imaging if I have an unruptured aneurysm?

The schedule depends on the aneurysm's size, location, and whether it's growing. Small, stable aneurysms might be checked every 1 to 2 years. Larger ones or those showing growth may need more frequent imaging. Your neurologist will recommend a schedule based on your aneurysm's characteristics.

Can an aneurysm heal on its own?

An unruptured aneurysm does not heal or go away on its own. It may stay the same size, grow slowly, or grow quickly. Monitoring with imaging tracks these changes. A ruptured aneurysm requires emergency treatment and cannot be left untreated.