An unruptured brain aneurysm is treated in one of three ways: watchful monitoring with regular imaging, a minimally invasive catheter-based procedure, or open surgery to clip the aneurysm shut. The right choice depends on the aneurysm’s size, location, and shape, along with your age and overall health. Many small aneurysms never need intervention at all.
Why Some Aneurysms Are Watched, Not Treated
Not every brain aneurysm requires a procedure. The five-year risk of rupture for a small aneurysm (under 7 mm) in a lower-risk location can be as low as 0.25% in people younger than 70 who don’t have high blood pressure. Because every procedure carries its own risks, treating a very low-risk aneurysm can be more dangerous than leaving it alone. On the other end of the spectrum, a large aneurysm (over 20 mm) in the back of the brain in an older person with hypertension and a history of bleeding can carry a five-year rupture risk above 15%, making treatment far more appealing.
Doctors use scoring tools that weigh several factors to estimate your personal rupture risk: the aneurysm’s size, its location in the brain, your age, whether you have high blood pressure, and whether you’ve ever had a previous brain bleed. There is no single millimeter cutoff that automatically triggers treatment. The decision is individualized, balancing the estimated rupture risk against the risks of the procedure itself.
If monitoring is recommended, you’ll typically get periodic brain imaging (usually MRA, a type of MRI that visualizes blood vessels without contrast dye) to check whether the aneurysm is growing or changing shape. Growth or a change in appearance often shifts the recommendation toward treatment.
Endovascular Coiling
Coiling is a catheter-based procedure, meaning there’s no open brain surgery. A thin tube is threaded from an artery in the groin up to the aneurysm in the brain. Once positioned, tiny platinum coils are packed inside the aneurysm sac as densely as possible. These coils trigger clotting, which seals off the aneurysm from normal blood flow and prevents it from rupturing.
In one study of 80 treated aneurysms, complete blockage was achieved in about 76% of cases, with near-complete blockage in another 10%. Partial reopening occurred in roughly 7.5% of treated aneurysms during follow-up, and this happened mostly in large or giant aneurysms (those over 15 mm). The retreatment rate for coiling is around 3.4%, which is higher than for surgical clipping, so follow-up imaging is important to confirm the coils are holding.
For wide-necked aneurysms, where coils might slip out of the sac and into the parent artery, doctors often use a supporting device. This could be a small stent placed across the neck of the aneurysm or a temporarily inflated balloon that holds the coils in place while they settle. About 60% of wide-necked aneurysms in one series required this kind of assistance.
Recovery After Coiling
Because there’s no incision in the skull, recovery is significantly faster than open surgery. The main discomfort is bruising and soreness at the groin where the catheter was inserted. You’ll generally need to avoid strenuous activity and hot baths for about a week. Hospital stays are shorter, often just one to two days, though reaction times can be slower during early recovery, so driving is off limits until your doctor clears you.
Flow Diverter Stents
Flow diverters are a newer endovascular option, delivered through a catheter the same way coils are. Instead of filling the aneurysm sac, a fine mesh stent is placed across the neck of the aneurysm in the parent artery. This mesh redirects blood flow away from the aneurysm, causing it to gradually clot and shrink over weeks to months.
Flow diverters were originally reserved for giant and large aneurysms that were difficult to treat with coiling. Over the past decade, their use has expanded to include smaller sidewall aneurysms and certain bifurcation aneurysms that are hard to reach or have awkward shapes for coil packing. They’re particularly useful for wide-necked aneurysms where coils alone won’t stay in place. After placement, you’ll need to take blood-thinning medication for a period to prevent clots from forming on the stent itself.
Surgical Clipping
Clipping is open brain surgery, performed under general anesthesia through a craniotomy, an opening made in the skull. The surgeon navigates to the aneurysm and places a small metal clip across its neck, permanently cutting off blood flow into the sac. The clip stays in your body for life. Once placed, the skull opening is secured with thin metal plates and screws, and the skin is closed with stitches.
The main advantage of clipping is durability. The retreatment rate is only about 0.27%, far lower than the 3.4% rate for coiling. Clipping also allows the surgeon to directly confirm the aneurysm is fully sealed during the operation. The mortality rate for clipping is approximately 1.8%, compared to about 2.3% for coiling, though complication rates vary depending on the aneurysm’s size and location.
Recovery After Clipping
You’ll wake up in the ICU or a hospital room and typically stay for several days. Pain at the incision site is common and can last several weeks. Muffled hearing on the side of the incision is normal, caused by fluid buildup, and usually clears within a few weeks. You may also notice a clicking noise when moving your head as the bone heals, which fades over time.
Jaw pain when eating or brushing teeth happens because muscles near the temple are moved during surgery. Gently exercising the jaw, opening and closing it about ten times, four to five times a day, helps speed recovery. If jaw pain persists beyond six weeks, physical therapy may be needed. Overall recovery from open surgery takes longer than from endovascular procedures, and you should expect several weeks before returning to normal activities. Reaction times may be slower during this period, so driving and similar tasks are restricted.
Coiling vs. Clipping: How They Compare
- Invasiveness: Coiling is minimally invasive with faster recovery. Clipping requires a craniotomy and a longer hospital stay.
- Durability: Clipping has a very low retreatment rate (0.27%). Coiling requires retreatment more often (3.4%), especially for larger aneurysms.
- Complication rates: Post-procedure complications occur in roughly 11% of clipping patients and 16% of coiling patients, though the types of complications differ.
- Best fit: Coiling tends to be preferred for aneurysms in deeper or harder-to-reach locations. Clipping may be favored for aneurysms with wide necks or complex shapes that don’t pack well with coils, though stent-assisted coiling and flow diverters have narrowed this gap.
Your neurosurgeon will recommend one approach over the other based on the aneurysm’s specific anatomy, your age, and your medical history. In many cases, both options are reasonable, and the decision involves weighing a quicker recovery against long-term durability.
Managing Blood Pressure and Lifestyle
Whether or not you have a procedure, controlling blood pressure is central to managing an unruptured aneurysm. High blood pressure puts constant outward force on the aneurysm wall, increasing both growth and rupture risk. Current clinical trials are comparing standard blood pressure targets (systolic 120 to 140 mmHg) against more aggressive lowering (below 120 mmHg) to determine which better prevents aneurysm growth and rupture. At minimum, keeping your blood pressure consistently in a healthy range matters.
Smoking is one of the strongest modifiable risk factors for both developing and rupturing brain aneurysms. Quitting reduces the mechanical stress on artery walls and slows the inflammatory damage that weakens them. Heavy alcohol use and stimulant drugs also raise rupture risk by causing sudden blood pressure spikes. Regular exercise, a healthy diet, and stress management all contribute to keeping blood pressure stable, which is the practical goal regardless of which treatment path you’re on.