Diagnosed With a Brain Aneurysm? Here's What Happens Next

Being told that a scan has found a brain aneurysm can understandably bring many questions. Could it rupture? Does it need surgery? And if your specialist recommends monitoring it instead, is it really safe to wait?

Finding a brain aneurysm does not automatically mean that treatment is required. Some unruptured brain aneurysms may be monitored, while others may benefit from treatment.

What happens next depends on the individual aneurysm and the person living with it. A neurosurgeon will assess several factors to determine the risk it may pose and whether monitoring or treatment may be appropriate.

What does it mean to have an unruptured brain aneurysm?

A brain aneurysm is a bulge that forms in a weakened area of the wall of a blood vessel in the brain. Risk factors include high blood pressure, cigarette smoking and family history. Brain aneurysms can occur in all age groups but have a higher incidence among those aged 40–60 and in women.

They are also more common than most people expect. Population studies estimate that roughly 3 in every 100 adults have an unruptured brain aneurysm, and the great majority will never know about it. Wider use of MRI and CT scanning means that more are now found incidentally, in people being scanned for headaches, dizziness, a head injury or as part of a health screening package.

An unruptured brain aneurysm has not burst and caused bleeding in the brain. Many unruptured aneurysms do not cause symptoms and may be discovered incidentally when a person undergoes a brain scan for another reason.

A ruptured brain aneurysm, on the other hand, causes bleeding in or around the brain and is a medical emergency.

Learn more about the symptoms and causes of brain aneurysms here.

How is a brain aneurysm found and confirmed?

Most unruptured aneurysms are first seen on one of three types of scan, and it is worth knowing which one you have, because they are not interchangeable.

CT angiography (CTA)

A CT scan performed with contrast dye injected into a vein. It is quick and widely available and is usually the first test when someone presents acutely or when an aneurysm is suspected on a plain scan. It involves a dose of radiation.

MR angiography (MRA)

An MRI-based study of the blood vessels. It involves no radiation and can often be performed without contrast, which makes it the usual choice for repeated monitoring over many years.

Digital subtraction angiography (DSA)

A catheter angiogram, in which a fine tube is passed from an artery in the wrist or groin and contrast is injected directly into the brain vessels. It gives the clearest picture of the aneurysm neck and the surrounding branches and remains the reference standard for planning treatment. Because it is an invasive procedure with a small risk of its own, it is reserved for situations where that extra detail will change the plan.

One practical point that surprises many patients: the measured size of the same aneurysm can differ by a millimetre or two between scan types, and even between projections on the same scan. This is part of why a single measurement is a weak basis for a decision, and why comparing like-for-like scans over time matters more than any one number.

Does every brain aneurysm need treatment?

No. Not every unruptured brain aneurysm needs to be treated immediately. In some people, the risk associated with treating an aneurysm may outweigh its estimated risk of rupture, and monitoring may therefore be recommended.

This is why discovering an aneurysm is usually followed by an individual assessment rather than an automatic recommendation for surgery.

The aim is to weigh two considerations:

• The likelihood that the aneurysm could grow or rupture in the future
• The potential risks and benefits of treating it

This balance will be different for every patient.

How do specialists decide whether a brain aneurysm needs treatment?

There isn't a single measurement or characteristic that determines whether an aneurysm should be treated. Your specialist will look at the aneurysm itself as well as factors relating to your health and medical history.

These factors are not weighed by intuition alone. Validated tools such as the PHASES score bring six of them together — population, hypertension, age, aneurysm size, earlier subarachnoid haemorrhage and aneurysm site — to produce an estimated five-year risk of rupture. In the pooled international data behind PHASES, the average risk across all unruptured aneurysms studied was around 1.4% over one year and 3.4% over five years. A score of this kind is a starting point for a conversation rather than a verdict, but it turns a frightening unknown into a figure you can actually weigh against the risk of treatment.

1. Size

The size of an aneurysm is one consideration when assessing its risk of rupture. However, size alone does not determine whether treatment is necessary.

A smaller aneurysm may still need closer assessment depending on its location, shape and other characteristics, while some aneurysms may be suitable for monitoring.

To give a sense of scale: in a large Japanese cohort of more than 6,000 unruptured aneurysms followed over time, the overall rupture rate was just under 1% per year. Aneurysms of 3 – 4mm ruptured at roughly 0.4% per year; those of 7 – 9mm carried around three times that risk, and those of 10mm or more considerably higher again.

Set against that, most aneurysms that do rupture measure less than 7mm. That is not a contradiction, small aneurysms are simply far more common, but it does mean that small is not the same as safe, which is exactly why size is never assessed on its own.

2. Location

Where an aneurysm occurs within the brain's blood vessels can influence both its estimated risk of rupture and the options available for treating it.

Aneurysms arising from the anterior communicating and posterior communicating arteries, and those in the posterior circulation (the vertebral and basilar arteries and their branches), carry a higher risk of rupture than aneurysms of the same size elsewhere.

Your specialist will therefore consider the aneurysm's location together with its other characteristics rather than assessing any single feature in isolation.

3. Shape and appearance

The shape and surface contour of an aneurysm carry information that size alone does not.

A daughter sac (a small blister arising from the main dome), an irregular or lobulated outline, and a high dome-to-neck ratio are all associated with an increased risk of rupture. The neck also has a direct bearing on treatment: a narrow-necked aneurysm is usually straightforward to coil, whereas a wide-necked one may need a stent, a balloon or a different technique altogether.

4. Whether the aneurysm is changing

If previous scans are available, your specialist may compare them to determine whether the aneurysm has changed in size or appearance over time.

Evidence of growth can affect how an aneurysm is managed.

An aneurysm that has demonstrably grown is regarded quite differently from one that has been stable for years, because documented growth is among the stronger signals that the wall is under stress. Changes of a millimetre have to be interpreted carefully, though, since some of that difference can come from the scan rather than the aneurysm — which is why serial imaging is ideally performed on the same modality each time.

5. Your age and overall health

Treatment itself carries risks, so your specialist will also consider your age, overall health and other medical conditions.

This helps determine whether the potential benefit of treating the aneurysm outweighs the risks associated with the procedure.

6. Your medical and family history

Certain health and lifestyle factors may also be considered, including high blood pressure and smoking.

A family history of brain aneurysms or aneurysmal rupture can also be relevant, particularly if close relatives have been affected.

Screening of unaffected relatives is generally offered where two or more first-degree relatives (a parent, sibling or child) have had a brain aneurysm or a subarachnoid haemorrhage, and to people with autosomal dominant polycystic kidney disease, in whom aneurysms are more common. A single affected relative does not usually warrant screening, but it is worth raising with your specialist.

“Almost every patient asks me first how big it is. Size does matter, but it is one of several things I weigh, including where the aneurysm sits, its shape, whether it has changed on previous scans, and the health and priorities of the person in front of me. My role is to bring those together, explain honestly what they mean, and reach a decision the patient feels settled about.”

—Dr Vincent Ng

If my aneurysm isn't treated, what happens next?

Being told that an aneurysm can be monitored rather than treated may initially sound worrying. However, monitoring does not mean ignoring the aneurysm.

Your specialist may recommend follow-up imaging to check whether its size or characteristics change over time.

The type and frequency of scans will depend on your individual condition, so there is no single monitoring schedule that applies to everyone.

In practice, a common pattern is a repeat scan at around six to twelve months to confirm the aneurysm is stable, then at progressively longer intervals if it remains unchanged. Some patients are eventually discharged from surveillance altogether; others, particularly younger patients, continue at intervals over many years.

Your specialist may also recommend addressing factors that can increase the risk of aneurysm growth or rupture, such as managing high blood pressure and stopping smoking.

If subsequent scans show changes to the aneurysm, your specialist can reassess whether continued monitoring or treatment is appropriate.

“When I tell a patient we will monitor an aneurysm, I want them to hear a plan rather than a postponement. Monitoring means agreed intervals for imaging, attention to blood pressure, support to stop smoking, and a clear understanding of what we are watching for and what would prompt us to act. Patients cope far better when they know exactly what is being done, and why.”

—Dr Vincent Ng

When might treatment for a brain aneurysm be recommended?

Treatment may be considered when your specialist determines that the potential risk posed by the aneurysm outweighs the risks associated with intervention.

The decision is individualised and may consider the aneurysm's:

• Size
• Location
• Shape and other characteristics
• Changes over time

As well as your:

• Age
• General health
• Medical history
• Family history
• Individual risk factors

If treatment is recommended, the next question is which approach is most suitable for your aneurysm.

How are brain aneurysms treated?

There are several ways of treating a brain aneurysm. The aim is generally to prevent blood from entering the aneurysm and reduce the risk of it rupturing.

The appropriate approach depends on factors including the aneurysm's location, size and shape, as well as your overall health.

Surgical clipping

During surgical clipping, a neurosurgeon accesses the aneurysm and places a small clip across its neck. This prevents blood from flowing into the aneurysm.

Clipping is performed through a craniotomy under general anaesthesia. Once a clip is correctly placed across the neck, the aneurysm is sealed permanently and rarely needs further treatment.

Endovascular coiling

A type of endovascular embolisation, coiling treats the aneurysm from within the blood vessel.

A thin catheter is guided through an artery towards the aneurysm. Small coils are then placed within the aneurysm to reduce blood flow into it and promote clotting, effectively sealing it off from the circulation.

Because the aneurysm is reached through the blood vessels, the procedure does not require opening the skull.

Flow diversion

For certain aneurysms, a flow-diverting stent may be considered. (A type of endovascular embolisation)

Rather than filling the aneurysm itself, the device is placed within the affected blood vessel to redirect blood flow away from the aneurysm, allowing it to gradually close off.

Other endovascular techniques

Aneurysms with a wide neck can be difficult to coil on their own. In these cases, a balloon may be used temporarily to hold the coils in place, a stent may be placed across the neck of the aneurysm, or an intrasaccular device such as a braided mesh implant may be positioned inside the aneurysm sac itself.

Not every technique is suitable for every aneurysm. Which options are open to you is determined largely by the anatomy of the aneurysm and the vessel it arises from.

Coiling or clipping: how do doctors decide?

There is no universally "better" treatment for every brain aneurysm.

A specialist may consider factors such as the aneurysm's size, shape and location, the anatomy of the surrounding blood vessels, whether the aneurysm has ruptured, and the patient's overall health when recommending an approach.

Each treatment also has its own potential benefits and risks, which should be discussed with your specialist.

What happens after treatment?

This is the part patients most often forget to ask about, and it matters for planning work and family life.

Most patients go home within a few days — typically a night or two after endovascular treatment (flow diversion or coiling), and a few days after clipping. Returning to everyday activity generally takes somewhere between one and a few weeks, depending on the procedure, the aneurysm treated, and your own rate of recovery. Your surgeon will give you a realistic timeframe for your situation before any decision is made.

Follow-up imaging is the usual practice after treatment.

It is however done more frequently and for a longer duration after coiling than after clipping. Your specialist will advise on driving, air travel, exercise, heavy lifting and, where relevant, pregnancy — most patients return to all of these activities, but the timing depends on the treatment and on your recovery.

Will I need medication after treatment?

Any treatment that leaves a stent or flow diverter inside the blood vessel normally requires a period of dual antiplatelet medication, typically aspirin together with a second agent started before the procedure and continued for months afterwards, often with aspirin continued long term. This carries a small bleeding risk of its own and needs to be planned around any other surgery or dental work. Clipping and standalone coiling do not require it. For some patients this is a decisive consideration, and it is worth raising early rather than after the decision is made.

What should I ask my neurosurgeon after a brain aneurysm diagnosis?

It can be difficult to remember what to ask after receiving an unexpected diagnosis. Consider bringing these questions to your consultation:

1. Where is my aneurysm located?
2. How large is it?
3. Are there features of my aneurysm that affect its risk of rupture?
4. Do you recommend monitoring or treatment, and why?
5. If we monitor it, what changes would make you reconsider treatment?
6. How often might I need follow-up imaging?
7. If treatment is recommended, what options are suitable for my aneurysm?
8. What are the benefits and risks of each treatment option?
9. Are there lifestyle or health factors I should manage?
10. What symptoms would require immediate medical attention?

If you are seeking another opinion, bringing your previous scan images and reports may also help your specialist understand how the aneurysm was discovered and assess its characteristics.

When is a brain aneurysm an emergency?

An unruptured brain aneurysm is different from a ruptured aneurysm.

When an aneurysm ruptures, bleeding can occur around the brain and urgent medical treatment is required.

A sudden, extremely severe headache, sometimes described as a thunderclap headache, is a characteristic warning sign of rupture. Other symptoms can include nausea and vomiting, neck stiffness, loss of consciousness, seizures, confusion or neurological changes.

In some patients, a smaller warning leak causes a sudden and unusually severe headache days or even weeks before a major rupture. This pain might settle after a while, and might be dismissed as a migraine. However, ignoring it at this juncture may potentially lead to patients missing the window to treat the aneurysm before the full rupture happens (and more brain damage has occurred). As such, any headache that reaches full intensity within seconds and is the worst you have ever experienced should be assessed urgently.

If you or someone around you develops symptoms that could indicate a ruptured brain aneurysm, seek medical attention immediately.

Getting clarity after a brain aneurysm diagnosis

A brain aneurysm diagnosis can sound frightening, but it does not tell you by itself what will happen next.

Some aneurysms may require treatment, while others can be monitored. Understanding the difference requires an assessment of the aneurysm's characteristics alongside your individual health and risk factors.

“A diagnosis like this is frightening, and that fear is entirely understandable. What helps most is clarity — knowing what the aneurysm is, what risk it genuinely carries, and what can be done about it. In my experience, most patients find the way forward far more manageable once they have that.”

—Dr Vincent Ng

At Mount Elizabeth Hospitals, our neurosurgeons can assess your condition, discuss the management options available and help you understand the next steps in your care.