Brain aneurysms are uncommon, but not rare
About 1 in 50 people has a brain aneurysm that has never ruptured. That means if you gathered 50 people in a room, roughly one of them would have one, though they might never know it. Most of these aneurysms stay small and cause no symptoms or problems over a person's lifetime.
The number of people who actually have a rupture is much smaller. Each year in the United States, roughly 30,000 people experience a ruptured brain aneurysm. That works out to about 1 rupture per 100,000 people annually, though this varies by age and other factors.
The gap between how many aneurysms exist and how many rupture matters because it means most people with an aneurysm never need treatment. Doctors often discover them by accident during imaging for an unrelated reason, and many people live their entire lives without knowing they have one.
Key Takeaways
- Approximately 1 in 50 people has a brain aneurysm that has never ruptured, making them far more common than ruptures.
- About 30,000 ruptured aneurysms occur each year in the United States, or roughly 1 per 100,000 people annually.
- Your risk of rupture depends on the aneurysm's size, location, shape, and your age, blood pressure, and smoking history.
- Unruptured aneurysms found by accident often require only monitoring with periodic imaging rather than immediate surgery.
- Family history of aneurysm or certain genetic conditions increases your lifetime risk of developing one.
Who is more likely to have a brain aneurysm
Age plays a role: aneurysms are rare in children and young adults but become more common as people age. Most ruptures happen between ages 40 and 65, though they can occur at any age.
Women are slightly more likely to have aneurysms than men, and the difference grows after age 50. However, men who do have aneurysms are more likely to experience a rupture.
Certain medical conditions raise your risk. High blood pressure is the strongest modifiable risk factor—it stresses the artery walls and makes rupture more likely. Smoking also increases risk significantly. People with connective tissue disorders like Ehlers-Danlos syndrome or Marfan syndrome have higher rates of aneurysms. Polycystic kidney disease, a genetic condition affecting the kidneys, is also associated with increased aneurysm risk.
Family history matters too. If a parent, sibling, or child has had a brain aneurysm, your lifetime risk is higher than the general population. The exact increase depends on how many relatives were affected and at what age.
How doctors find aneurysms you don't know you have
Most unruptured aneurysms are discovered by accident. A person gets a CT scan or MRI for a headache, stroke symptoms, or another reason entirely, and the radiologist spots the aneurysm in the images.
Screening—looking for aneurysms in people with no symptoms—is not routine for the general population. However, doctors may recommend screening for people with a strong family history of aneurysm or rupture, or for those with certain genetic conditions. Screening typically uses CT angiography or MR angiography, both of which create detailed images of blood vessels in the brain.
Once an unruptured aneurysm is found, your doctor will assess the risk that it might rupture. Factors they consider include the aneurysm's size (larger ones rupture more often), its shape (irregular shapes are riskier), where it is located in the brain, your age, whether you smoke, and your blood pressure control. Based on this assessment, your doctor will recommend either monitoring with repeat imaging every few years or preventive treatment.
Why most unruptured aneurysms don't need surgery
The decision to treat an unruptured aneurysm is not automatic. Surgery or other procedures carry their own risks—infection, stroke, or bleeding—so doctors weigh the chance the aneurysm will rupture against the chance the treatment itself will cause harm.
For small aneurysms in low-risk locations, the annual rupture rate is very low, sometimes less than 1 percent per year. For these cases, monitoring with imaging every one to three years is often safer than operating. Your doctor will discuss the specific numbers for your aneurysm and help you decide whether to watch and wait or proceed with treatment.
Larger aneurysms, those in high-risk locations, or those with irregular shapes may warrant preventive treatment. The two main options are surgical clipping (a neurosurgeon places a clip across the aneurysm's neck to stop blood flow into it) or endovascular coiling (a neurointerventionalist threads a catheter into the artery and fills the aneurysm with coils). Your doctor will recommend the approach that fits your specific situation.
Ruptured aneurysms are a medical emergency
When an aneurysm ruptures, blood spills into the space around the brain, causing what doctors call a subarachnoid hemorrhage. This is a life-threatening emergency requiring immediate hospital care.
Symptoms of a rupture include a sudden, severe headache (often described as "the worst headache of my life"), neck stiffness, sensitivity to light, nausea, vomiting, and sometimes loss of consciousness. If you or someone near you experiences these symptoms, call 911 immediately.
About half of people who experience a ruptured aneurysm die from the initial bleed or complications within the first month. Of those who survive, some have permanent neurological damage. This is why preventing rupture through monitoring or treatment of unruptured aneurysms matters, and why recognizing rupture symptoms and seeking emergency care immediately can affect outcomes.
How lifestyle changes affect your aneurysm risk
If you have been diagnosed with an unruptured aneurysm, controlling your blood pressure becomes especially important. High blood pressure puts stress on the aneurysm wall and increases rupture risk. Your doctor may prescribe blood pressure medication or recommend dietary changes like reducing salt intake and increasing physical activity.
Smoking significantly increases the risk that an aneurysm will rupture. If you smoke, quitting reduces your risk. The benefit begins immediately and continues to grow over time.
Avoiding sudden, extreme increases in blood pressure also matters. This means limiting strenuous exercise, avoiding stimulants like cocaine, and managing stress where possible. Your doctor can advise you on what level of physical activity is safe for your situation.
Alcohol use, particularly heavy drinking, may increase rupture risk. Moderate consumption is generally considered safer, but your doctor can give you specific guidance based on your aneurysm's characteristics.
What happens after an aneurysm rupture
After emergency treatment to stop the bleeding, recovery involves time in an intensive care unit where doctors monitor for complications. These can include rebleeding, vasospasm (narrowing of blood vessels that reduces blood flow to the brain), hydrocephalus (buildup of fluid in the brain), and seizures.
Rehabilitation after a rupture often takes months or longer. Some people recover fully, while others experience lasting effects like weakness, speech difficulties, memory problems, or changes in mood or personality. The outcome depends on the severity of the initial bleed, how quickly treatment was given, the person's age, and overall health.
Long-term follow-up imaging is standard after a rupture to make sure the aneurysm has been fully treated and to watch for any new aneurysms, since people who have had one rupture have a slightly higher risk of developing another.
Frequently Asked Questions
Can a small brain aneurysm grow larger over time?
Yes, some aneurysms grow, though many stay the same size for years or even a lifetime. Growth rate varies widely. This is one reason doctors recommend periodic imaging for unruptured aneurysms—to catch growth early if it occurs. Your doctor will tell you how often you need follow-up scans based on your aneurysm's initial size and characteristics.
If my parent had a brain aneurysm, will I definitely get one?
No. Family history increases your risk, but it does not may provide you will develop an aneurysm. Your doctor may recommend screening with imaging, especially if your parent had a rupture or if multiple family members were affected. Screening can find aneurysms early if they do develop, when treatment options are broader.
Can stress cause a brain aneurysm to rupture?
Sudden emotional stress can temporarily raise blood pressure, which theoretically could trigger a rupture in someone with a very fragile aneurysm. However, rupture is more closely tied to the aneurysm's size, shape, and location than to stress alone. Managing stress is still worthwhile for overall health and blood pressure control.
What should I do if I have been told I have an unruptured aneurysm?
Follow your doctor's recommendations for monitoring, which typically means repeat imaging at intervals they specify. Control your blood pressure, stop smoking if you do, and avoid sudden strenuous activity unless your doctor says it is safe. Keep all follow-up appointments and report any new symptoms like headaches or vision changes to your doctor right away.
Are there warning signs before an aneurysm ruptures?
Most ruptures happen without warning. Some people report a sudden, brief headache or neck pain in the days or weeks before a rupture, but this is not common enough to be reliable. If you have an unruptured aneurysm and experience a sudden, severe headache unlike any you have had before, seek emergency care immediately.