A cerebral aneurysm isn’t something you hear about often-until it’s too late. It’s a weak spot in a blood vessel in your brain that balloons out like a tiny balloon. Most people live with one for years without knowing. But if it bursts, it can cause a life-threatening bleed in the brain called a subarachnoid hemorrhage. About 3.2% of people worldwide have one of these unruptured aneurysms, and roughly 1 in 10,000 people will have one rupture every year. The good news? Not all aneurysms burst. The bad news? When they do, 30 to 40% of people don’t make it past the first day. That’s why understanding your risk-and what to do about it-isn’t just medical knowledge. It’s survival.
What Makes an Aneurysm Likely to Burst?
It’s not just about size. A 5 mm aneurysm in one spot might be harmless, but the same size in another location could be ticking time bomb. The risk comes down to a mix of things you can’t change and things you can.
Age is a big one. People over 65 are nearly three times more likely to have a rupture than younger adults. Women are also more at risk than men-about 1.6 times more likely to develop them. If you have two or more close relatives who’ve had a brain aneurysm, your risk jumps fourfold. That’s not just coincidence. Genetics play a real role.
But here’s where you still have control: your lifestyle. High blood pressure is the number one modifiable risk. If your systolic pressure is above 140 mmHg, your rupture risk more than doubles. Smoking? Even worse. Current smokers face over three times the risk of non-smokers. And it’s not just about whether you smoke-it’s how much. People who smoke 10 or more cigarettes a day see their risk climb by nearly half. Heavy drinking-more than 14 drinks a week-adds another 32% to your chances.
Shape, Location, and Blood Flow Matter More Than You Think
Size matters, but not the way you’d guess. An aneurysm larger than 7 mm has over three times the risk of bursting compared to smaller ones. But here’s the twist: some aneurysms under 5 mm rupture anyway. Why? Because location and shape are just as important.
Aneurysms at the anterior communicating artery (AComm) are especially dangerous. They rupture more often than others-even when they’re small. In fact, they’re 2.4 times more likely to burst than aneurysms elsewhere. Distal parts of the anterior cerebral artery can rupture at sizes under 5 mm. The middle cerebral artery aneurysms? They carry a rupture risk nearly four times higher than average.
Shape is another clue. Aneurysms that aren’t round-those with bumps, lobes, or “daughter sacs”-are far more unstable. Studies show these irregular shapes increase rupture risk by 68%. If the wall of the aneurysm looks bumpy or uneven under imaging, that’s a red flag.
And it’s not just anatomy. Blood flow patterns inside the aneurysm matter too. Low, swirling, or oscillating blood flow (called low wall shear stress) is present in 83% of ruptured aneurysms-but only 42% of unruptured ones. This means the way blood pushes against the weakened wall can literally tear it apart over time.
The PHASES Score: Your Personal Rupture Risk Calculator
Doctors don’t guess whether an aneurysm will burst. They use tools. The most trusted one is called the PHASES score. It combines six factors: your population background, blood pressure, age, aneurysm size, whether you’ve had a previous bleed, and where the aneurysm is located.
Each factor adds a point. A score of 0-3 means you have a 3% chance of rupture in five years. A score of 6? That jumps to 18%. At 9 or 10 points? Your risk hits 45%. That’s not a small number. If your score is 6 or higher, treatment is usually recommended. If it’s below 6, and the aneurysm is small and in a low-risk spot, watching it with yearly scans might be safer than intervening.
There’s also the triple-S model-size, site, shape. It’s newer, but it’s accurate. After detecting growth in an aneurysm, this model can predict your risk over 6 months, 1 year, or 2 years. At one year, it ranges from 2.1% to 10.6%. That’s precise enough to guide decisions.
Treatment Options: Clipping, Coiling, and Flow Diversion
If your aneurysm is high-risk, you have three main options: surgical clipping, endovascular coiling, or flow diversion.
Surgical clipping is the oldest method. A neurosurgeon opens your skull (craniotomy), finds the aneurysm, and places a tiny titanium clip across its neck. It stops blood from entering the bulge. Success rates? About 95% of aneurysms are fully blocked. The cure is permanent in 88-92% of cases. But it’s invasive. Recovery takes weeks. Complication rates are higher in older patients-35% more risk if you’re over 70.
Endovascular coiling is less invasive. A catheter is threaded from your groin up into the brain. Platinum coils are packed into the aneurysm, causing a clot to form inside. It seals off the bulge. At six months, 78-85% of aneurysms are completely blocked. It’s better for older patients and those with other health problems. The ISAT trial showed coiling cut 1-year death risk by over 22% compared to clipping. But here’s the catch: you’re more likely to need a second procedure. About 15.7% of coiled aneurysms need retreatment over 12 years, compared to just 6.2% for clipped ones.
Flow diversion is the newest option. It uses a mesh stent-like the Pipeline Embolization Device or WEB device-that’s placed across the artery where the aneurysm sits. Blood flows through the mesh, away from the aneurysm. Over time, the aneurysm shrinks and disappears. It’s especially good for wide-necked or giant aneurysms. The PED-PLATINIUM trial showed 85.5% complete occlusion at one year. The WEB device, approved in 2019, works well for aneurysms at branch points and showed 71.4% success at one year. But it’s not for everyone. It takes months for the aneurysm to fully close, and you need to take blood thinners during that time.
Who Gets Which Treatment?
There’s no one-size-fits-all. Your choice depends on:
- Aneurysm size and shape: Wide-necked aneurysms (>4 mm) often need flow diversion. Irregular shapes respond better to coiling or clipping.
- Location: Aneurysms in the back of the brain (posterior circulation) have 22% higher complication rates with clipping. Coiling or flow diversion are often preferred here.
- Your age and health: If you’re over 70 or have heart disease, surgery is riskier. Coiling or flow diversion are safer choices.
- Previous rupture: If you’ve had one rupture, your chance of another is over five times higher. Treatment is almost always recommended.
For unruptured aneurysms under 5 mm in the front of the brain, the UCAS Japan study found a 0.2% risk of rupture over five years. That’s so low, many doctors just monitor them with yearly MRA scans.
Medical Management: The Silent Shield
Treatment isn’t just surgery or coils. Sometimes, the best thing you can do is change how you live.
Controlling blood pressure is non-negotiable. Target systolic pressure below 130 mmHg. That alone can cut rupture risk significantly. Quitting smoking? Within two years, your rupture risk drops by 54%. Cutting back on alcohol helps too. These aren’t just “good habits”-they’re life-saving actions.
There’s no magic pill, but research is moving fast. Scientists are now looking at genetic markers-17 specific gene locations linked to aneurysm formation and rupture. In the future, a simple blood test might tell you your personal risk level. Machine learning models are already analyzing 42 different features of an aneurysm-from its shape to how blood flows around it-to predict rupture better than current scores.
What Happens After Treatment?
Successful treatment doesn’t mean you’re out of the woods forever-but it changes everything. Without treatment, a ruptured aneurysm has a 68% chance of re-bleeding within a decade. With successful intervention? That drops to just 2.3%.
Quality of life matters too. People who get coiling or flow diversion report better daily function and mental health one year after treatment than those who had surgery. EQ-5D scores (a standard health quality measure) show 0.82 for endovascular patients versus 0.76 for surgical patients. That’s not just a number. It means more energy, less pain, and better ability to work, move, and enjoy life.
Long-term follow-up is essential. Even after successful coiling or flow diversion, you need imaging every 1-2 years to make sure the aneurysm stays sealed. A small recurrence can be caught early and fixed before it becomes dangerous.