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Definition
A brain aneurysm is a bulge in an artery in your brain. The most common type of brain aneurysm looks like a round berry — attached to your artery by a tiny neck. As long as the aneurysm is small and doesn't rupture, it poses little risk to your health. Such aneurysms may go undetected indefinitely and produce no signs or symptoms.
But some brain aneurysms are large enough to put pressure on surrounding brain tissue. Others may rupture at a weak spot in the artery wall, flooding an area of your brain with blood. A ruptured aneurysm may quickly become life-threatening and requires prompt medical attention.
In the United States, between 2 percent and 5 percent of the population — up to 15 million people — have or will have berry-type (saccular) brain aneurysms. But fewer than 30,000 of these aneurysms rupture each year. Most aneurysms, particularly small ones, don't rupture.
People of all ages can have a brain aneurysm, but they're more common in adults than children. Women are slightly more likely to develop an aneurysm than men are. How serious an aneurysm is depends on its size and location and on your age and health. Small unruptured aneurysms are often best left alone, though treatments are available for larger aneurysms.
Symptoms
An unruptured brain aneurysm may produce no symptoms, particularly if it's small. However, a large aneurysm may press on brain tissues and nerves, possibly causing:
- Pain above and behind the eye
- Numbness, weakness or paralysis of one side of the face
- A dilated pupil
- Vision changes, including double vision
- Drooping of an eyelid
If an aneurysm ruptures, signs and symptoms may include:
- Sudden, extremely severe headache
- Nausea and vomiting
- Stiff neck
- Double vision
- Loss of consciousness
Causes
Most brain aneurysms develop as a result of the wear and tear on arteries that comes with aging. Aneurysms often form at forks or branches in arteries because those sections of the vessel are weaker. Rarely, a blow to your head or an infection in an artery can weaken an artery wall and result in an aneurysm.
Risk factors
Brain aneurysms sometimes run in families. Your risk increases dramatically if two or more of your close family members have had brain aneurysms. These familial aneurysms also tend to rupture at a smaller size and at a younger age than other types of brain aneurysms. Siblings often experience rupture in the same decade of life.
Other risk factors may include:
- Hypertension. Blood pressure readings over 160/95 have in some studies been linked to the formation and rupture of brain aneurysms. But it appears that rapid, short-term increases in blood pressure — such as those experienced when straining to lift a heavy load — may be more of a link than chronic hypertension.
- Smoking. The more cigarettes you smoke, the higher your risk of a ruptured brain aneurysm. Cigarette smokers with high blood pressure are 15 times more likely to experience a ruptured brain aneurysm than are nonsmokers who don't have high blood pressure. Smokers are also more likely to develop unruptured aneurysms and multiple aneurysms.
In addition, several medical conditions have been associated with the development of brain aneurysms, including:
- Polycystic kidney disease, in which the kidneys and occasionally other organs develop multiple cysts
- Arteriovenous malformation, a condition in which an abnormal connection exists between arteries and veins in the brain
- A narrowing of the aorta at birth (coarctation)
- Connective tissue disorders, such as Ehlers-Danlos syndrome and pseudoxanthoma elasticum
When to seek medical advice
A ruptured aneurysm is generally considered a medical emergency. About 40 percent of the people whose aneurysm has burst don't survive the first 24 hours. Another 25 percent die of complications within six months.
Seek immediate medical attention if you develop a sudden, extremely severe headache — particularly if it's accompanied by nausea and vomiting.
If you're with someone who complains of a sudden, severe headache or who loses consciousness or has a seizure, call 911 or emergency medical help and get the person to a doctor immediately.
Tests and diagnosis
An aneurysm is likely to go undetected until it either ruptures or shows up on a brain imaging test that you might undergo for another condition. However, your doctor may suggest that you undergo screening scans if you have two or more close family members who have had brain aneurysms.
The two most common screening scans — computerized tomography (CT) and magnetic resonance imaging (MRI) — can also confirm suspected aneurysm ruptures. More risky tests, such as cerebral arteriograms and spinal taps, typically are reserved for times when aneurysm ruptures are suspected.
Computerized tomography (CT)
CT scans use special X-ray equipment to take views from several different angles. These views are combined to show slices of your brain's structures.
There's no special preparation for the test, although you'll need to hold still so that the images don't blur. Scans are painless and usually only take a few minutes. You'll lie on a table that slides into the machine. In many cases, contrast dye is injected intravenously to provide more detailed images.
Magnetic resonance imaging (MRI)
MRIs use a strong magnetic field and radio waves to create detailed, cross-sectional images of your brain. You are not allowed to wear anything containing metal as it will distort the images. You'll lie on a narrow table that slides into the machine.
Several sets of images are needed, and each can take as long as 15 minutes. You must hold very still during scans, to avoid blurring the image. MRI scans are painless but some people experience a feeling similar to claustrophobia inside the machine. If you think this will be a problem for you, your doctor can prescribe medicine to help you relax. In many cases, contrast dye is injected intravenously to provide more detailed images.
Cerebral arteriogram
During this procedure, your doctor inserts a thin, flexible tube (catheter) into a large artery — usually in your groin — and threads it past your heart into the cerebral arteries in your brain. A special dye injected into the catheter fills your arteries so that they show up better on the X-rays.
Your head will be immobilized so that the images won't be blurred, and you'll lie on an X-ray table. You may be given a sedative or pain pill before the procedure. Your skin will be numbed at the insertion site, but you'll feel a brief, sharp pain as the catheter is inserted into the artery. You may feel a warmth or burning as the dye is injected.
Spinal tap
If your CT head scan is negative, but you have symptoms of a ruptured aneurysm, your doctor may want you to have a spinal tap. Also known as a lumbar puncture, this procedure involves placing a needle between the vertebrae in your lower back to extract a small amount of the fluid that protects your brain and spinal cord. Analysis of the fluid can detect brain hemorrhage.
You will lie on your side, with your knees pulled up to your chest and your chin tucked downward. It may become uncomfortable to maintain this position, but it's important to remain curled up so that the needle doesn't accidentally hurt your spinal cord.
Your skin will be numbed, but it may hurt when the needle goes through the tissue surrounding your spinal cord. The pain should stop in just a few seconds. The entire procedure takes about a half-hour, and you'll need to stay in the hospital for a few hours afterward for observation.
Complications
A brain aneurysm that bursts can cause stroke, permanent nerve damage or death. The blood that escapes from a burst aneurysm can damage or even destroy nearby brain cells, interfering with the way your brain works.
A delayed complication of a burst aneurysm is called vasospasm — a narrowing of the blood vessels, which can starve the brain of nutrients and oxygen. The most common time for vasospasm to occur is between four days and two weeks after the aneurysm ruptures.
Blood from a ruptured aneurysm also can block the circulation of cerebrospinal fluid and allow this fluid to accumulate in the brain. This problem, called hydrocephalus, can increase the pressure inside your skull and harm your brain.
Treatments and drugs
The decision to treat an unruptured aneurysm depends on a number of factors, including the type, location and size of the aneurysm, your age, and your general health. Most unruptured aneurysms less than 7 millimeters across — about the size of a pencil eraser — appear to pose little risk of rupture, whereas the risk of treating aneurysms may be significant. Many are best left untreated. If you have a large aneurysm that hasn't burst, especially if it's pressing against brain tissue and causing signs and symptoms, such as headaches or impaired vision, you're more likely to need treatment.
Treatment options for ruptured and unruptured brain aneurysms include:
- Microvascular clipping. This surgical procedure is performed with general anesthesia. The neurosurgeon removes a section of your skull to access the aneurysm. and locates the blood vessel that feeds the aneurysm. Then he or she places a tiny metal clip on the neck of the aneurysm to stop blood flow to it.
- Endovascular embolization. This is a less invasive alternative to surgical clipping. You're given general anesthesia or sedation. The doctor then inserts a hollow plastic tube (catheter) into an artery, usually in your groin, and threads it through your body to the aneurysm. He or she then uses a guide wire to push a spiral of soft platinum wire through the catheter and into the aneurysm. The wire coils up inside the aneurysm, blocking the blood flow and causing the blood to clot.
Both procedures pose risks. The endovascular coil is less invasive and has a quicker recovery time, but it also has a higher risk of re-bleeding, so additional procedures may be necessary. The surgical clip procedure may be a better choice for people who have larger or more-complicated aneurysms, although the risks involved with the surgery increase substantially in people over age 50.
Other treatments for ruptured brain aneurysms are aimed at relieving signs and symptoms. They may include:
- Medications. Anticonvulsant medications can prevent seizures, analgesics may relieve headache symptoms, and calcium channel blockers can help widen narrowed blood vessels.
- Shunt surgery. If you develop hydrocephalus, you may need to have surgery to insert a shunt system to carry excess cerebrospinal fluid out of your brain. This system, which consists of a flexible silicone rubber tube (shunt) and a valve, creates a drainage channel that starts in your brain and ends in your abdominal cavity.
Prevention
To prevent the development of a brain aneurysm or lessen the risk of rupture:
- Don't smoke or use stimulant drugs. Both can cause a sudden increase in blood pressure and damage arteries.
- Limit caffeine intake. Caffeine is a stimulant that can cause a sudden increase in blood pressure.
- Avoid straining. Sudden, forceful and sustained exertion of the type you expend when you lift heavy weights can cause a sudden increase in blood pressure.
- Be cautious of aspirin use. If you have an aneurysm, talk to your doctor before taking aspirin or other drugs that inhibit blood clotting because they may increase blood loss if you hemorrhage.
Last Updated: 05/23/2007
