Most aneurysms produce no symptoms at all, which is what makes them so difficult to detect on your own. About 1% of the general population has a brain aneurysm without knowing it. The signs you can watch for depend on where the aneurysm is located and whether it’s still intact or has started to leak or rupture. Some types produce subtle warning signs as they grow, while others stay completely silent until they become emergencies.
Why Most Aneurysms Cause No Symptoms
An aneurysm is a weak, ballooning spot in an artery wall. It can form in the brain, the chest, the abdomen, or behind the knee. When the bulge is small and stable, blood flows through normally and nothing feels different. Brain aneurysms smaller than 7 millimeters rarely cause symptoms and are the most commonly detected type, usually found by accident during imaging for something else entirely.
This is the frustrating reality: you can’t feel an aneurysm forming. There is no blood test for it. The only reliable way to find one before it causes problems is through imaging, and routine screening is only recommended for specific high-risk groups.
Warning Signs of a Brain Aneurysm
An unruptured brain aneurysm that’s growing large enough to press on nearby nerves or brain tissue can produce localized symptoms. These tend to develop gradually and may include pain above and behind one eye, a drooping eyelid, a dilated pupil, double or blurred vision, or numbness on one side of the face. These signs are uncommon, but they suggest the aneurysm is big enough to compress surrounding structures.
A ruptured brain aneurysm is a medical emergency with unmistakable symptoms. The hallmark is a thunderclap headache: a sudden, explosive headache that reaches maximum intensity within seconds and is often described as the worst headache of your life. This is not a headache that builds slowly over hours. It hits all at once. Along with the headache, a rupture typically causes nausea and vomiting, a stiff neck, sensitivity to light, blurred or double vision, confusion, seizures, and sometimes loss of consciousness.
A leaking aneurysm, where a small amount of blood seeps out before a full rupture, can cause a sudden severe headache that lasts several days to two weeks. This is sometimes called a “sentinel headache” and is essentially a warning that a full rupture may follow. Any sudden, unusually severe headache that feels different from headaches you’ve had before warrants emergency evaluation.
Signs of an Abdominal Aortic Aneurysm
The aorta is the body’s largest artery, running from the heart down through the chest and abdomen. When an aneurysm develops in the abdominal section, it often grows slowly and silently for years. As it expands, you may notice a deep, constant pain in your belly or along your side, back pain that doesn’t seem tied to movement or posture, or a throbbing or pulsing sensation near your belly button. Some people or their doctors can actually feel the pulsation during a physical exam.
If an abdominal aortic aneurysm ruptures, the pain is sudden, severe, and persistent in the belly or back, often described as a ripping or tearing sensation. Blood pressure drops rapidly and the pulse speeds up. This is a life-threatening emergency.
Signs of a Chest (Thoracic) Aortic Aneurysm
Aneurysms in the chest portion of the aorta are harder to detect because their symptoms overlap with many common conditions. As a thoracic aneurysm grows, it can press on nearby structures and cause back pain, chest tenderness, a persistent cough, shortness of breath, or a weak and scratchy voice. If the aneurysm tears (a condition called aortic dissection), it can cause difficulty swallowing along with severe chest or back pain.
Aneurysms in the Legs
The most common peripheral aneurysm forms in the popliteal artery behind the knee. Most people with one have no symptoms whatsoever. Problems arise when a blood clot forms inside the aneurysm and either blocks blood flow or sends clot fragments downstream into the lower leg. Signs of this include pain, numbness, coldness, pale skin, and muscle weakness in the affected leg. A ruptured popliteal aneurysm causes pain behind the knee along with swelling and bruising.
Who Should Get Screened
Because most aneurysms are silent, screening is the only way to catch them early. Current guidelines from the U.S. Preventive Services Task Force recommend a one-time abdominal ultrasound for men aged 65 to 75 who have ever smoked (defined as 100 or more cigarettes in a lifetime). Men in that age range who have never smoked may still benefit from selective screening based on other risk factors. For women who have never smoked and have no family history, routine screening is not recommended.
Brain aneurysm screening follows different logic. About 1% of the general population has one, but in families where aneurysms run, the risk climbs as high as 30%. If you have two or more first-degree relatives (a parent, sibling, or child) who have had a brain aneurysm, screening with brain imaging is generally recommended. Your doctor can order a non-invasive scan to check.
How Aneurysms Are Diagnosed
When doctors suspect an aneurysm or want to screen for one, they use imaging. For abdominal aortic aneurysms, a simple ultrasound is the standard screening tool: painless, quick, and highly accurate.
For brain aneurysms, the two primary options are CT angiography (CTA) and MR angiography (MRA). Both involve imaging the blood vessels after enhancing them with contrast dye or specialized sequences. CTA has a sensitivity of about 95% and a specificity of roughly 96%, meaning it catches nearly all aneurysms and rarely flags something that isn’t one. MRA has caught up in sensitivity (also around 95%) but is slightly less specific, meaning it occasionally produces false positives. The gold standard remains catheter-based angiography, where a thin tube is threaded into the arteries for direct imaging, but this is invasive and typically reserved for cases where the non-invasive scans are inconclusive or treatment planning requires more detail.
What Happens After One Is Found
Finding an unruptured aneurysm does not automatically mean surgery. The decision depends on its size, location, whether it’s growing, your age, and your overall health. Brain aneurysms smaller than 7 millimeters in the front part of the brain’s circulation have a very low annual rupture risk, around 0.36% to 0.5% per year for aneurysms between 3 and 6 millimeters. That risk rises sharply with size: 7 to 9 millimeter aneurysms rupture at about 1.7% per year, and aneurysms 10 millimeters or larger carry a 4.4% annual risk or higher.
For small, stable aneurysms, the typical approach is regular monitoring with repeat imaging every 6 to 12 months to check for growth. If an aneurysm is documented to be enlarging, treatment is strongly recommended regardless of its current size. People with a family history of aneurysms may be offered treatment at smaller sizes than usual because their risk profile is different.
For abdominal aortic aneurysms, the same principle applies. Small ones are monitored with periodic ultrasounds, while those reaching a certain diameter (typically around 5 to 5.5 centimeters) are referred for repair. Treatment options for both brain and aortic aneurysms range from minimally invasive catheter-based procedures to open surgery, depending on the aneurysm’s characteristics.
Risk Factors That Raise Your Odds
Certain factors make aneurysms more likely and can help you gauge whether screening or further evaluation makes sense for you. The major ones include smoking (the single biggest modifiable risk factor for aortic aneurysms), high blood pressure, a family history of aneurysms, age over 50, and connective tissue disorders that weaken artery walls. Women are more likely than men to have brain aneurysms, while men are more likely to develop abdominal aortic aneurysms. Heavy alcohol use and using stimulant drugs also increase risk, particularly for brain aneurysms.
If multiple risk factors apply to you and you’re experiencing any of the subtle symptoms described above, bringing it up with your doctor and asking about imaging is a reasonable step. If you experience a sudden, explosive headache or sudden severe abdominal or back pain, that is not a wait-and-see situation.