Brain aneurysm risk factors

What is a cerebral aneurysm?

An aneurysm is a weak area in a blood vessel that usually enlarges. It’s often described as a “ballooning” of the blood vessel. Watch an animation.

How do aneurysms form? Are people born with an aneurysm?

People usually aren’t born with aneurysms. Most develop after age 40. Aneurysms usually develop at branching points of arteries and are caused by constant pressure from blood flow. They often enlarge slowly and become weaker as they grow, just as a balloon becomes weaker as it stretches. Aneurysms may be associated with other types of blood vessel disorders, such as fibromuscular dysplasia, cerebral arteritis or arterial dissection, but these are very unusual. Some aneurysms are due to infections, drugs such as amphetamines and cocaine, or direct brain trauma from an accident.

How is an aneurysm diagnosed?

Special imaging tests can detect a brain aneurysm. In the CTA (computed tomographic angiography), patients are placed on a table that slides into a CT scanner. A special contrast material (dye) is injected into a vein, and images are taken of the blood vessels to look for abnormalities such as an aneurysm. In the second test, called MRA (magnetic resonance angiography), patients are placed on a table that slides into a magnetic resonance scanner, and the blood vessels are imaged to detect a cerebral aneurysm.

The most reliable test is called a diagnostic cerebral angiogram. In this test, the patient lies on an X-ray table. A small tube (catheter) is inserted through a blood vessel in the leg (groin) and guided into each of the blood vessels in the neck that go to the brain. Contrast is then injected, and pictures are taken of all the blood vessels in the brain. This test is slightly more invasive and less comfortable.

Before any treatment is considered, a diagnostic cerebral angiogram is usually performed to fully map a plan for therapy.

If one aneurysm forms, will others form? Having one aneurysm means there’s about a 20 percent chance of having one or more other aneurysms.

What are the symptoms of an unruptured aneurysm? Smaller aneurysms usually don’t have symptoms. But as an aneurysm enlarges, it can produce headaches or localized pain. If an aneurysm gets very large, it may produce pressure on the normal brain tissue or adjacent nerves. This pressure can cause difficulty with vision, numbness or weakness of an arm or leg, difficulty with memory or speech, or seizures.

What causes an aneurysm to bleed?

We usually don’t know why an aneurysm bleeds or exactly when it will bleed. We do know what increases the chance for bleeding:

High blood pressure is the leading cause of subarachnoid hemorrhage. Heavy lifting or straining can cause pressure to rise in the brain and may lead to an aneurysm rupture.

Strong emotions, such as being upset or angry, can raise blood pressure and can subsequently cause aneurysms to rupture.

*Blood thinners (such as warfarin), some medications and prescription drugs (including diet pills that act as stimulants such as ephedrine and amphetamines), and harmful drugs like cocaine can cause aneurysms to rupture and bleed.

What are the chances that an unruptured aneurysm may bleed? Many factors determine whether an aneurysm is likely to bleed. These include the size, shape and location of the aneurysm and symptoms that it causes. Smaller aneurysms that are uniform in size may be less likely to bleed than larger, irregularly shaped ones. Once an aneurysm has bled, there’s a very high chance of re-bleeding.

What happens if an aneurysm bleeds? If an aneurysm ruptures, it leaks blood into the space around the brain. This is called a “subarachnoid hemorrhage.” Depending on the amount of blood, it can produce:

  • a sudden severe headache that can last from several hours to days
  • nausea and vomiting drowsiness and/or coma

The hemorrhage may also damage the brain directly, usually from bleeding into the brain itself. This is called a “hemorrhagic stroke.” This can lead to:

  • weakness or paralysis of an arm or leg
  • trouble speaking or understanding language
  • vision problems
  • seizures

What is the usual damage to the brain after an aneurysm bleeds?

Once an aneurysm bleeds, the chance of death is about 40 percent and the chance of some brain damage is about 66 percent, even if the aneurysm is treated. If the aneurysm isn’t treated quickly enough, another bleed may occur from the already ruptured aneurysm.

Vasospasm (irritation by the leaked blood causing narrowing of the blood vessels) is a common complication following a ruptured aneurysm. This can lead to further brain damage. Other problems may include hydrocephalus (enlargement of the spaces within the brain that produce cerebrospinal fluid), difficulty breathing that requires a mechanical ventilator, and infection.

Why is the damage so extensive after bleeding? After blood enters the brain and the space around it, direct damage to the brain tissue and brain function results. The amount of damage is usually related to the amount of blood. Damage is due to the increased pressure and swelling from bleeding directly into the brain tissue, or from local cellular damage to brain tissue from irritation of blood in the space between the brain and the skull.

Blood can also irritate and damage the normal blood vessels and cause vasospasm (constriction). This can interrupt normal blood flow to the healthy brain tissue and can cause even more brain damage. This is called an “ischemic stroke.”

Will treating a ruptured aneurysm reverse or improve brain damage? Once an aneurysm bleeds and brain damage occurs, treating the aneurysm will not reverse the damage. Treatment helps prevent more bleeding.

How is a treatment method for an aneurysm chosen? Doctors must evaluate the risk factors that favor treatment vs. non-treatment and decide which technique may be best. It’s important to consult with experts in this field. This should include a cerebrovascular neurosurgeon who specializes in surgically clipping aneurysms, a neurosurgeon with endovascular expertise and training, a neurointerventionalist (a neurologist with endovascular training) or a neuroradiologist who specializes in the less invasive treatment of cerebral aneurysms by coiling.

How should an aneurysm be treated?

The best treatment depends on many things, including whether the aneurysm has ruptured or not. A ruptured aneurysm usually requires treatment right away. However, the treatment time and options depend on the size, location and shape of the aneurysm, as well as the patient’s overall medical condition. If an aneurysm hasn’t ruptured, the treatment decision depends on its size, location and shape, and the patient’s symptoms

What treatments are available?

  • Medical therapy.  Small, unruptured aneurysms that aren’t creating any symptoms may not need treatment unless they grow, trigger symptoms or rupture. It’s very important to have annual check-ups to monitor blood pressure, cholesterol and other medical conditions.
  • Neurosurgery. Depending on a person’s risk factors, open surgery may be recommended. Patients are placed under general anesthesia, and the neurosurgeon places a surgical clip around the base of the aneurysm.
  • Neurointerventionalist/neuroradiologist. Depending on the aneurysm’s size, location and shape, it may be treatable from inside the blood vessel. This minimally invasive procedure is similar to the cerebral angiogram. However, in addition to taking pictures, a catheter is directed through the blood vessels into the aneurysm itself. Then, using X-ray guidance, the endovascular surgeon carefully places soft platinum micro-coils into the aneurysm and detaches them. The coils stay within the aneurysm and act as a mechanical barrier to blood flow, thus sealing it off

What are the potential complications of aneurysm treatment?

Until the aneurysm is safely and completely treated, there’s always the risk it may re-bleed and cause more brain damage. If normal blood vessels are damaged, it could also result in more brain damage.

What follow-up is required after aneurysm treatment? Depending on the type of treatment, the two follow-up procedures are:

  • Surgical clipping. After this type of surgery, a post-operative angiogram is usually performed during the hospital stay to make sure the surgical clip has completely treated the aneurysm.
  • Neurointerventionalist/neuroradiologist. After coiling an aneurysm, a routine follow-up angiogram is usually performed six to 12 months after the procedure to make sure the aneurysm remains blocked off

Understanding aneurysms

What you need to know about these uncommon but much-feared blood vessel abnormalities.

Published: January, 2019

Each year, tens of thousands of people discover they have a bulging blood vessel in their brain, chest, or abdomen. Known as aneurysms, these bulges or balloon-like pouches form at a weak spot along an artery. The most common — and most dangerous — are in the brain or along the body’s largest blood vessel, the aorta (see illustration).

Because aneurysms are uncommon, doctors don’t screen for them routinely. Most are found by accident during tests such as an ultrasound or MRI scan done for other reasons. Of course, some aren’t discovered until they leak or burst, often without any warning signs. The potentially fatal consequences of that bleeding explain why most people associate aneurysms with a sense of dread. However, understanding the underlying causes can help you prevent them and know whether you should undergo any screening tests.

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Brain aneurysm

Increased risk

There are a number of things that can increase your risk of developing a brain aneurysm. These are discussed below.


Smoking tobacco can significantly increase your risk of developing a brain aneurysm.

Studies have shown the majority of people diagnosed with a brain aneurysm smoked, or had done so in the past.

The risk is particularly high in people with a family history of brain aneurysm.

Exactly why smoking increases the risk of brain aneurysms is unclear. It may be that the harmful substances in tobacco smoke damage the walls of your blood vessels.

High blood pressure

High blood pressure can place increased pressure on the walls of the blood vessels inside the brain, increasing your chances of developing an aneurysm.

You’re more likely to develop high blood pressure if you:

  • are overweight
  • have a relative with high blood pressure
  • are of African or Caribbean descent
  • eat a lot of salt
  • don’t eat enough fruit and vegetables
  • don’t do enough exercise
  • drink a lot of coffee or other caffeine-based drinks
  • drink a lot of alcohol
  • are aged over 65

Family history

Having a first-degree relative, such as a parent, brother or sister, with a history of a brain aneurysm means you’re more likely to develop one than someone with no family history of the condition.

But the increased risk is still small: only around 1 in 50 people with a family history of a ruptured brain aneurysm have a rupture themselves.


Your risk of developing a brain aneurysm increases as you get older, with most cases diagnosed in people over the age of 40.

This may be because the walls of the blood vessels are weakened over time by the constant pressure of blood flowing through them.


Women are more likely to develop a brain aneurysm than men. This may be because levels of a hormone called oestrogen lower significantly after the menopause. Oestrogen is thought to help maintain the elasticity of the blood vessels.

Pre-existing weakness in the blood vessels

In some cases, brain aneurysms are caused by weaknesses in the blood vessels present from birth.

Severe head injury

A brain aneurysm can develop after a severe brain injury if the blood vessels in the brain are damaged, although this is very rare.

Cocaine abuse

Cocaine abuse is considered to be another risk factor for brain aneurysms. Cocaine can inflame the walls of the blood vessels and raise your blood pressure. The combination of these 2 factors increases your risk of developing a brain aneurysm.

Autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic condition that causes multiple cysts to develop on the kidneys. Cysts are small sacs filled with fluid.

Around 1 in every 1,000 people is born with ADPKD. Of these people, around 1 in 20 develop an aneurysm in the brain.

Body tissue disorders

Your risk of developing a brain aneurysm can be higher if you have a condition that affects your body tissues, such as Ehlers-Danlos syndrome or Marfan syndrome.

This is because these conditions can sometimes cause weaknesses in the walls of your blood vessels.

Coarctation of the aorta

People with coarctation of the aorta are also at an increased risk of developing a brain aneurysm.

Coarctation of the aorta is the term used to describe narrowing of the main artery in the body (the aorta), which is present from birth (congenital). It is a common type of congenital heart disease.

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