Brain Aneurysm

What is brain aneurysm?

A brain aneurysm, also called a cerebral aneurysm or intracranial aneurysm, is a weak, bulging spot in the wall of a blood vessel (artery) in the brain. Because the vessel wall is thinner at this point, blood pressure can push it outward over time, forming a small sac or balloon-like pouch. Many people ask “what is brain aneurysm and how dangerous is it?” — the honest answer is that it depends. Most brain aneurysms are small, never cause symptoms, and are found by chance during scans done for other reasons. A smaller number grow, press on nearby structures, or rupture (burst). A ruptured brain aneurysm causes bleeding around the brain, most often a type of bleed called a subarachnoid hemorrhage (bleeding into the space between the brain and the thin membranes that cover it). This is a medical emergency.

Brain aneurysms can occur in anyone, but they are most often discovered in adults between roughly 30 and 60 years of age, and they are diagnosed somewhat more often in women than in men. They are uncommon in children, although they can occur at any age. Some people have more than one aneurysm at the same time. In medical coding, an unruptured cerebral aneurysm is classified under ICD-10 code I67.1.

It helps to understand two broad situations, because they are managed very differently:

• Unruptured aneurysm: the vessel wall is bulging but intact. Many of these are monitored or treated preventively.
• Ruptured aneurysm: the wall has torn and blood has leaked around the brain. This requires emergency care.

Symptoms of a brain aneurysm

Brain aneurysm symptoms differ sharply depending on whether the aneurysm is unruptured, leaking slightly, or fully ruptured. This is one of the most important things for patients to understand.

Unruptured aneurysm

Most unruptured brain aneurysms cause no symptoms at all. When an aneurysm is large enough to press on nearby nerves or brain tissue, possible symptoms may include:

• Pain above or behind one eye
• A dilated (enlarged) pupil in one eye
• Double vision or other changes in vision
• A drooping eyelid
• Numbness or weakness on one side of the face

These symptoms develop because the aneurysm is pushing on structures such as the nerves that control eye movement. They do not always mean rupture is about to happen, but they should always be evaluated promptly by a doctor.

Leaking (“sentinel”) aneurysm

In some cases, an aneurysm leaks a small amount of blood before a larger rupture. This can cause a sudden, severe headache that may improve on its own. Doctors sometimes call this a sentinel or warning headache. Because a larger rupture may follow, any sudden, unusually severe headache deserves urgent medical assessment.

Ruptured aneurysm

A ruptured brain aneurysm typically causes dramatic, sudden symptoms. Classic warning signs include:

• A sudden, extremely severe headache — often described as “the worst headache of my life” or a “thunderclap” headache that peaks within seconds
• Nausea and vomiting
• A stiff neck
• Sensitivity to light
• Blurred or double vision
• Seizure (uncontrolled shaking or loss of awareness)
• Confusion, drowsiness, or loss of consciousness
• Weakness or numbness, often on one side of the body

A ruptured aneurysm is life-threatening. Anyone with these symptoms needs emergency medical care immediately.

Causes and risk factors

Brain aneurysm causes are usually a combination of factors rather than a single event. Aneurysms tend to form at points where arteries branch, because the vessel wall is naturally under more stress there. Over years, a combination of inherited wall weakness and wear from blood flow and blood pressure can allow a bulge to develop.

Factors that are widely accepted to increase the risk of developing a brain aneurysm, or of an existing aneurysm rupturing, include:

• Smoking: one of the strongest modifiable risk factors for both formation and rupture
• High blood pressure (hypertension): ongoing pressure stresses the artery walls
• Family history: having close relatives (such as a parent or sibling) with a brain aneurysm increases risk
• Age: risk rises with age; aneurysms are most often found in adults over 30
• Sex: aneurysms are diagnosed more often in women, particularly after menopause
• Heavy alcohol use and stimulant drug use (for example, cocaine or amphetamines)
• Certain inherited conditions: such as autosomal dominant polycystic kidney disease and some connective tissue disorders (conditions affecting the body’s structural proteins, such as Ehlers-Danlos syndrome or Marfan syndrome)
• Arteriovenous malformations (AVMs): abnormal tangles of blood vessels in the brain, which can be associated with aneurysms
• Head injury or infection: rarely, trauma or an infected artery wall can produce an aneurysm

Some of these factors, such as age and family history, cannot be changed. Others — especially smoking and untreated high blood pressure — can be addressed, and doing so is a central part of reducing risk whether or not an aneurysm is ever treated with a procedure.

Diagnosis

Brain aneurysm diagnosis depends on the situation. Many unruptured aneurysms are discovered incidentally, meaning they show up on a brain scan ordered for another reason, such as headaches or dizziness. When doctors suspect an aneurysm — or when a rupture is suspected — they use a combination of imaging tests:

• CT scan (computed tomography): a fast X-ray–based scan of the brain. It is usually the first test when a rupture is suspected, because it detects fresh bleeding around the brain very well.
• CT angiography (CTA): a CT scan performed with a contrast dye injected into a vein, which highlights the brain’s arteries and can show the aneurysm’s size, shape, and location.
• MRI and MR angiography (MRA): scans that use magnetic fields rather than X-rays. MRA can show the arteries without radiation and is often used to monitor known aneurysms over time.
• Cerebral angiography (catheter angiography or DSA): a thin tube (catheter) is guided through blood vessels, usually from the groin or wrist, to the arteries supplying the brain, and dye is injected. This gives the most detailed pictures of an aneurysm and is often used when planning treatment. It is generally considered the most precise test for mapping brain aneurysms.
• Lumbar puncture (spinal tap): if a rupture is strongly suspected but the CT scan appears normal, doctors may sample the fluid around the spinal cord to look for traces of blood.

When an unruptured aneurysm is found, doctors assess its size, shape, and location, along with the patient’s age, overall health, family history, and risk factors. All of these details influence whether the recommendation is monitoring or preventive treatment. In many hospitals, this evaluation is coordinated by a neurology department working together with neurosurgeons and interventional radiologists (doctors who treat blood vessels from the inside using catheters).

Treatment options for brain aneurysm

Brain aneurysm treatment is highly individualized. There is no single correct approach for every patient, and the risks of treating an aneurysm must always be weighed against the risk of leaving it alone. The main options are described below.

Watchful waiting (active monitoring)

Many small, unruptured aneurysms have a low risk of rupture, and in these cases doctors often recommend monitoring rather than immediate intervention. This usually involves repeat imaging (often MRA or CTA) at intervals your doctor sets, to check whether the aneurysm is growing or changing shape. Monitoring is an active medical decision, not “doing nothing” — it is paired with strict control of risk factors, especially quitting smoking and treating high blood pressure.

Medication and risk-factor management

There is no medication that shrinks or repairs an aneurysm itself. However, medicines play an important supporting role. Your doctor may prescribe blood pressure medication to reduce stress on the artery wall, and support to stop smoking. After a rupture, additional medicines are used in the hospital — for example, drugs that help prevent vasospasm (a dangerous narrowing of brain arteries that can occur in the days after a bleed), pain relief, and anti-seizure medication when needed.

Endovascular procedures

Endovascular means “inside the blood vessel.” These minimally invasive procedures are performed through a catheter threaded from an artery in the groin or wrist up to the brain, so no opening of the skull is needed:

• Coiling (endovascular coiling): tiny, soft platinum coils are packed into the aneurysm sac. The coils encourage the blood inside to clot, sealing the aneurysm off from circulation.
• Stent-assisted coiling: a small mesh tube (stent) is placed in the artery to hold coils in place when the aneurysm has a wide opening.
• Flow diversion: a fine mesh device is placed across the neck of the aneurysm inside the parent artery. It redirects blood flow past the aneurysm, allowing the sac to gradually close over time. Flow diverters are often used for large or complex aneurysms.

Endovascular treatment generally involves a shorter hospital stay and recovery than open surgery, but not every aneurysm is suitable for it, and some treated aneurysms need follow-up imaging or, occasionally, retreatment.

Surgical clipping

In microsurgical clipping, a neurosurgeon opens a small window in the skull (a craniotomy) and places a tiny metal clip across the neck of the aneurysm, sealing it off from blood flow permanently. Clipping is a long-established treatment and can be very durable. It is a more invasive operation with a longer recovery, and the choice between clipping and endovascular treatment depends on the aneurysm’s location, shape, and size, as well as the patient’s age and health. These decisions are usually made by a multidisciplinary team.

Emergency treatment of a ruptured aneurysm

When an aneurysm has ruptured, the priorities are to stabilize the patient, secure the aneurysm as soon as safely possible (by coiling or clipping) to prevent re-bleeding, and manage complications such as vasospasm and hydrocephalus (a buildup of fluid in the brain that sometimes requires a drainage tube or shunt). Care after a rupture typically takes place in an intensive care unit.

Aneurysms in children

Brain aneurysms in children are rare and often differ from adult aneurysms in cause and behavior. When they occur, evaluation and treatment are usually handled by teams experienced in pediatric neurosurgery, because children’s blood vessels, anatomy, and recovery patterns are not the same as adults’. At hospital groups such as Acibadem, this care is coordinated between pediatric and neurovascular specialists.

Living with brain aneurysm / outlook

Being told you have a brain aneurysm — especially one found by chance — can be frightening. It may help to know that most unruptured aneurysms never rupture, and many people live full, normal lives with a small aneurysm that is simply monitored. Still, the outlook varies from person to person and depends on the aneurysm’s size, shape, and location, your age and health, and whether it has bled.

For people living with a known, unruptured aneurysm, doctors commonly advise:

• Stop smoking completely — this is one of the most meaningful steps you can take
• Keep blood pressure well controlled and take prescribed medication consistently
• Limit alcohol and avoid stimulant drugs
• Attend all follow-up imaging appointments so any change is caught early
• Ask your doctor about specific activities — most everyday exercise is considered safe for many patients, but recommendations are individual

After a ruptured aneurysm, recovery is often gradual and can take months. Some people recover well; others experience lasting effects such as fatigue, headaches, memory or concentration difficulties, or emotional changes including anxiety and depression. Rehabilitation — which may include physical, occupational, and speech therapy, as well as psychological support — plays an important role. It is honest to say that outcomes after rupture range widely, and no doctor can guarantee a particular result. What is consistent across studies and clinical experience is that rapid emergency treatment and structured rehabilitation give patients the best chance of a good recovery.

Anxiety about a known aneurysm is common and understandable. Talking openly with your care team about your actual, individualized risk — rather than worst-case scenarios — often helps. Support from family, counselors, or patient groups can also make living with the diagnosis easier.

Frequently asked questions

What is a brain aneurysm in simple terms?

A brain aneurysm is a weak spot in the wall of an artery in the brain that bulges outward like a small balloon. Most cause no symptoms and are found by chance on scans. The main concern is that some aneurysms can rupture and bleed, which is a medical emergency — but most never do.

How serious is a brain aneurysm?

It depends on the situation. An unruptured aneurysm may pose little immediate danger and can often be monitored or treated preventively. A ruptured aneurysm, by contrast, is life-threatening and requires emergency treatment. Your doctor can estimate your personal risk based on the aneurysm’s size, shape, and location and your overall health.

Can a brain aneurysm heal on its own?

In general, an aneurysm does not disappear or repair itself, although small aneurysms may remain stable for many years without ever causing a problem. There is no medication that shrinks an aneurysm. If treatment is needed, it involves sealing the aneurysm off through an endovascular procedure or surgery. This is why regular monitoring, when recommended, is important.

What are the warning signs of a brain aneurysm rupture?

The hallmark sign is a sudden, extremely severe headache that peaks within seconds — often described as the worst headache of a person’s life. It may be accompanied by a stiff neck, nausea and vomiting, sensitivity to light, blurred or double vision, seizure, confusion, or loss of consciousness. These symptoms require immediate emergency care.

What causes a brain aneurysm to form?

Aneurysms usually develop over years, at branch points in arteries where the wall is under more stress. Contributing factors include smoking, high blood pressure, older age, family history, heavy alcohol use, and certain inherited conditions such as polycystic kidney disease and some connective tissue disorders. Often several factors act together rather than a single cause.

How is a brain aneurysm diagnosed?

Doctors confirm a brain aneurysm with imaging. CT angiography and MR angiography show the brain’s arteries in detail, and catheter cerebral angiography provides the most precise pictures, especially when planning treatment. If a rupture is suspected, a plain CT scan is usually done first to look for bleeding, sometimes followed by a lumbar puncture if the scan is unclear.

How long does recovery take after brain aneurysm treatment?

Recovery varies widely. After a planned endovascular procedure for an unruptured aneurysm, many people return to normal activities within days to weeks. Recovery after open surgical clipping generally takes longer. After a rupture, recovery is measured in months and often involves rehabilitation. Your care team can give you a realistic timeline for your specific situation.

When to see a doctor

Seek emergency medical care immediately (call your local emergency number) if you or someone near you experiences any of the following red-flag signs, which may indicate a ruptured brain aneurysm:

• A sudden, severe “thunderclap” headache — the worst headache you have ever had, reaching peak intensity within seconds
• Headache with a stiff neck, vomiting, or sensitivity to light
• Sudden loss of consciousness, fainting, or a seizure
• Sudden confusion, drowsiness, or difficulty speaking
• Sudden weakness or numbness, especially on one side of the body or face
• Sudden vision changes, such as double vision or loss of vision

Make a prompt (non-emergency) appointment with a doctor if you notice a drooping eyelid, a newly enlarged pupil, persistent pain behind one eye, or new double vision — these can be signs of an unruptured aneurysm pressing on nearby nerves. You should also consider discussing screening with your doctor if two or more close family members have had a brain aneurysm, or if you have an inherited condition known to increase risk. Early evaluation allows you and your care team to make informed decisions before an emergency ever occurs.