Medically reviewed by Drugs.com. Last updated on Apr 27, 2022.
A brain aneurysm (AN-yoo-riz-um) is a bulge or ballooning in a blood vessel in the brain. An aneurysm often looks like a berry hanging on a stem.
A brain aneurysm can leak or rupture, causing bleeding into the brain (hemorrhagic stroke). Most often, a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. This type of hemorrhagic stroke is called a subarachnoid hemorrhage.
A ruptured aneurysm quickly becomes life-threatening and requires prompt medical treatment.
Most brain aneurysms, however, don't rupture, create health problems or cause symptoms. Such aneurysms are often detected during tests for other conditions.
Treatment for an unruptured brain aneurysm may be appropriate in some cases and may prevent a rupture in the future. Talk with your health care provider to ensure you understand the best options for your specific needs.
An aneurysm is a ballooning at a weak spot in an artery wall. An aneurysm's walls can be thin enough to rupture. The illustration shows an individual with an unruptured aneurysm. The inset shows what happens when the aneurysm ruptures.
A sudden, severe headache is the key symptom of a ruptured aneurysm. This headache is often described as the "worst headache" ever experienced.
In addition to a severe headache, common signs and symptoms of a ruptured aneurysm include:
- Nausea and vomiting
- Stiff neck
- Blurred or double vision
- Sensitivity to light
- A drooping eyelid
- Loss of consciousness
In some cases, an aneurysm may leak a slight amount of blood. This leaking may cause only a sudden, extremely severe headache.
A more severe rupture often follows leaking.
An unruptured brain aneurysm may produce no symptoms, particularly if it's small. However, a larger unruptured aneurysm may press on brain tissues and nerves, possibly causing:
- Pain above and behind one eye
- A dilated pupil
- A change in vision or double vision
- Numbness of one side of the face
When to see a doctor
Seek immediate medical attention if you develop a:
- Sudden, extremely severe headache
If you're with someone who complains of a sudden, severe headache or who loses consciousness or has a seizure, call 911 or your local emergency number.
Brain aneurysms develop as a result of thinning artery walls. Aneurysms often form at forks or branches in arteries because those areas of the vessels are weaker.
Although aneurysms can appear anywhere in the brain, they are most common in arteries at the base of the brain.
The causes of most brain aneurysm are unknown, but a range of factors may increase your risk.
A number of factors can contribute to weakness in an artery wall and increase the risk of a brain aneurysm or aneurysm rupture. Brain aneurysms are more common in adults than in children. They're also more common in women than in men.
Some of these risk factors develop over time, while others are present at birth.
Risk factors that develop over time
- Older age
- Cigarette smoking
- High blood pressure
- Drug abuse, particularly the use of cocaine
- Heavy alcohol consumption
Some types of aneurysms may occur after a head injury or from certain blood infections.
Risk factors present at birth
Some conditions that are present at birth can be associated with an elevated risk of developing a brain aneurysm. These include:
- Inherited connective tissue disorders, such as Ehlers-Danlos syndrome, that weaken blood vessels
- Polycystic kidney disease, an inherited disorder that results in fluid-filled sacs in the kidneys and usually increases blood pressure
- Narrow aorta (coarctation of the aorta), the large blood vessel that delivers oxygen-rich blood from the heart to the body
- Brain arteriovenous malformation (AVM), in which the arteries and veins in the brain are tangled, interrupting blood flow
- Family history of brain aneurysm, particularly a first-degree relative, such as a parent, brother, sister or child
When a brain aneurysm ruptures, the bleeding usually lasts only a few seconds. However, the blood can cause direct damage to surrounding cells, and the bleeding can damage or kill other cells. It also increases pressure inside the skull.
If the pressure becomes too high, it may disrupt the blood and oxygen supply to the brain and loss of consciousness or even death may occur.
Complications that can develop after the rupture of an aneurysm include:
- Re-bleeding. An aneurysm that has ruptured or leaked is at risk of bleeding again. Re-bleeding can cause further damage to brain cells.
- Narrowed blood vessels in the brain. After a brain aneurysm ruptures, blood vessels in the brain may contract and narrow (vasospasm). This condition can cause an ischemic stroke, in which there's limited blood flow to brain cells, causing additional cell damage and loss.
- A buildup of fluid within the brain (hydrocephalus). Most often, a ruptured brain aneurysm occurs in the space between the brain and the thin tissues covering the brain. The blood can block the movement of fluid that surrounds the brain and spinal cord. As a result, an excess of fluid puts pressure on the brain and can damage tissues.
- Change in sodium level. Bleeding in the brain can disrupt the balance of sodium in the blood. This may occur from damage to the hypothalamus, an area near the base of the brain. A drop in blood sodium levels can lead to swelling of brain cells and permanent damage.
If you experience a sudden, severe headache or other symptoms that could be related to a ruptured aneurysm, you'll be given tests to determine whether you've had bleeding into the space between your brain and surrounding tissues (subarachnoid hemorrhage). The tests can also determine if you've had another type of stroke.
You may also be given tests if you show symptoms of an unruptured brain aneurysm, such as pain behind the eye, changes in vision or double vision.
Diagnostic tests include:
Computerized tomography (CT). A CT scan, which is a specialized X-ray exam, is usually the first test used to determine if you have bleeding in the brain or some other type of stroke. The test produces images that are 2D "slices" of the brain.
With this test, you may also receive an injection of a dye that makes it easier to observe blood flow in the brain and may indicate the presence of an aneurysm. This variation of the test is called a CT angiogram.
Cerebrospinal fluid test. If you've had a subarachnoid hemorrhage, there will most likely be red blood cells in the fluid surrounding your brain and spine (cerebrospinal fluid). If you have symptoms of a ruptured aneurysm but a CT scan doesn't shown evidence of bleeding, a test of your cerebrospinal fluid can help make a diagnosis.
The procedure to draw cerebrospinal fluid from your back with a needle is called a lumbar puncture.
Magnetic resonance imaging (MRI). This imaging technique uses a magnetic field and radio waves to create detailed images of the brain, either 2D images or 3D images.
A type of MRI that assesses the arteries in detail — called MR angiography — may detect the presence of an aneurysm.
Cerebral angiogram. During this procedure, a thin, flexible tube (catheter) is inserted into a large artery, usually in the groin or the wrist. The catheter threads past your heart to the arteries in your brain. A special dye injected into the catheter travels to arteries throughout your brain.
A series of X-ray images can then reveal details about the condition of your arteries and detect an aneurysm. A cerebral angiogram — also called a cerebral arteriogram — is usually used when other diagnostic tests don't provide enough information.
Screening for brain aneurysms
The use of imaging tests to screen for unruptured brain aneurysms is generally not recommended unless you're at high risk. Talk to your health care provider about the potential benefit of a screening test if you have:
- A family history of brain aneurysms. Particularly if two first-degree relatives — your parents or siblings — have had brain aneurysms.
- A congenital disorder that increases your risk of developing a brain aneurysm — such as polycystic kidney disease, coarctation of the aorta or Ehlers-Danlos syndrome, among others.
There are two common treatment options for a ruptured brain aneurysm.
- Surgical clipping is a procedure to close off an aneurysm. The neurosurgeon removes a section of your skull to access the aneurysm and locates the blood vessel that feeds the aneurysm. Then the neurosurgeon places a tiny metal clip on the neck of the aneurysm to stop blood flow into it.
Endovascular treatment is a less invasive procedure than surgical clipping. The surgeon inserts a catheter into an artery, usually in your wrist or groin, and threads it through your body to the aneurysm.
The surgeon then uses a device — a flow diverter, an intraluminal flow disrupter, a stent or coils — or different combinations of various devices to destroy the aneurysm from inside the blood vessel.
Both procedures pose potential risks, particularly bleeding in the brain or loss of blood flow to the brain. The endovascular coil is less invasive and may be initially safer, but it may carry a slightly higher risk of needing a repeat procedure in the future due to the aneurysm reopening.
Newer treatments available for brain aneurysm include tubular stent-like implants (flow diverters) that work by diverting blood flow away from an aneurysm sac. The diversion stops blood movement within the aneurysm and stimulates the body to heal the site, encouraging reconstruction of the parent artery. Flow diverters may be particularly useful in larger aneurysms that can't be safely treated with other options.
Your neurosurgeon or interventional neuroradiologist, in collaboration with your neurologist, will make a recommendation based on the size, location and overall appearance of the brain aneurysm, your ability to undergo a procedure, and other factors.
Other treatments for ruptured aneurysms
Other treatments for ruptured brain aneurysms are aimed at relieving symptoms and managing complications.
- Pain relievers, such as acetaminophen (Tylenol, others), may be used to treat headache pain.
Calcium channel blockers prevent calcium from entering cells of the blood vessel walls. These medications may lessen the risk of having serious symptoms from the erratic narrowing of blood vessels (vasospasm) that may be a complication of a ruptured aneurysm.
One of these medications, nimodipine (Nymalize), has been shown to reduce the risk of delayed brain injury caused by insufficient blood flow after subarachnoid hemorrhage from a ruptured aneurysm.
Interventions to prevent stroke from insufficient blood flow include IV injections of a drug to dilate the blood vessels, which elevates blood pressure to overcome the resistance of narrowed blood vessels.
An alternative intervention to prevent stroke is angioplasty. In this procedure, a surgeon uses a catheter to inflate a tiny balloon that expands a narrowed blood vessel in the brain caused by vasospasm. A drug known as a vasodilator also may be used to expand blood vessels in the affected area.
- Anti-seizure medications may be used to treat seizures related to a ruptured aneurysm. These medications include levetiracetam (Keppra), phenytoin (Dilantin, Phenytek, others), valproic acid and others. Their use has been debated by several experts, and is generally subject to caregiver discretion, based on the medical needs of each individual.
Ventricular or lumbar draining catheters and shunt surgery can lessen pressure on the brain from excess cerebrospinal fluid (hydrocephalus) associated with a ruptured aneurysm. A catheter may be placed in the spaces that are filled with fluid inside the brain or in the area surrounding the brain and spinal cord to drain the excess fluid into an external bag.
Sometimes it may then be necessary to introduce a shunt system — which consists of a flexible silicone rubber tube and a valve — that creates a drainage channel starting in the brain and ending in the abdominal cavity.
- Rehabilitative therapy. Damage to the brain from a subarachnoid hemorrhage may result in the need for physical, speech and occupational therapy to relearn skills.
Treating unruptured brain aneurysms
A surgical clip, an endovascular coil or a flow diverter can be used to seal off an unruptured brain aneurysm and help prevent a future rupture. However, in some unruptured aneurysms, the known risks of the procedures may outweigh the potential benefit.
A neurologist, in collaboration with a neurosurgeon or interventional neuroradiologist, can help you determine whether the treatment is appropriate for you.
Factors to consider in making treatment recommendations include:
- The aneurysm size, location, degree of irregularity of the aneurysm and overall appearance of the aneurysm
- Your age and general health
- Family history of ruptured aneurysm
- Congenital conditions that increase the risk of a ruptured aneurysm
If you have high blood pressure, talk to your health care provider about medication to manage the condition. If you have a brain aneurysm, proper control of blood pressure may lower the risk of rupture.
In addition, if you smoke cigarettes, talk with your care provider about strategies to stop smoking since cigarette smoking is a risk factor for formation, growth and rupture of the aneurysm.
Lifestyle changes to lower your risk
If you have an unruptured brain aneurysm, you may lower the risk of its rupture by making these lifestyle changes:
- Don't smoke or use recreational drugs. If you smoke or use recreational drugs, talk to your health care provider about strategies or an appropriate treatment program to help you quit.
- Control your blood pressure if you have high blood pressure.
- Eat a healthy diet and exercise. Changes in diet and exercise can help lower blood pressure. Talk to your health care provider about changes that are appropriate for you.
A surgical procedure to treat brain aneurysms involves opening the skull, finding the affected artery and then placing a metal clip over the neck of the aneurysm.
With endovascular coiling, the surgeon feeds a soft, flexible wire into the aneurysm via a catheter. The wire coils inside the aneurysm and seals off the aneurysm from the artery.
Coping and support
The Brain Aneurysm Foundation offers information on connecting with support groups in many states and in other countries, including the Mayo Clinic Brain Aneurysm Support Group.
Preparing for an appointment
Brain aneurysms are often detected after they've ruptured and become medical emergencies. However, a brain aneurysm may be detected when you've undergone head-imaging tests for another condition.
If such test results indicate you have a brain aneurysm, you'll need to discuss the results with a specialist in brain and nervous system disorders (neurologist, neurosurgeon or neuroradiologist).
What you can do
To make the best use of your time with your health care provider, you may want to prepare a list of questions, such as:
- What do you know about the size, location and overall appearance of the aneurysm?
- Do the imaging test results provide evidence of how likely it is to rupture?
- What treatment do you recommend at this time? What are the risks of treatment?
- If I wait, how often will I need to have follow-up tests?
- What steps can I take to lower the risk of an aneurysm rupturing?
What to expect from your doctor
Your neurologist, neurosurgeon or neuroradiologist may ask you the following questions to help determine the best course of action:
- Do you smoke?
- How much alcohol do you drink?
- Do you use recreational drugs?
- Are you being treated for high blood pressure?
- Do you take your medications as prescribed by your health care provider?
- Is there a history of brain aneurysm or brain aneurysm rupture in your family?