By Chris Woolston
CONSUMER HEALTH INTERACTIVE

The human brain contains a dense network of blood vessels that are normally sturdy enough to last a lifetime. But if you have high blood pressure, a head injury, a brain infection, or a defect at birth, the walls of one or more of these vessels may become thin and weak. As blood presses against the weak spot, the artery begins to bulge. This bulge is called a brain aneurysm.

According to a recent report from the Mayo Clinic, up to 15 million Americans -- about 5 percent of the population -- have brain aneurysms. The vast majority aren't aware of the condition. As long as the vessel wall remains intact, aneurysms are silent problems that rarely cause any symptoms. Most brain aneurysms are asymptomatic, meaning that they haven't ruptured or caused any problems at all.

Unfortunately, even though most brain aneurysms never cause any problems, they still carry the potential for disaster. As reported by the National Institute of Neurological Disorders and Stroke, as many as 10 in every 100,000 people a year have aneurysms that rupture. When an aneurysm ruptures, blood spills into the brain, often disrupting the organ's vital functions. This bleeding in the brain is called a hemorrhagic stroke.

According to the National Institutes of Health, victims of ruptured aneurysms can be divided into four groups. Forty percent die within 24 hours, 25 percent die in the next six months, others survive with significant disabilities (such as paralysis and mental impairment), and some survive with few or no lingering problems. Patients who receive prompt treatment have the best chance of leading a normal life afterward.

A sudden, severe headache is often the first sign of a ruptured aneurysm (hemorrhagic stroke). Patients typically describe it as the worst headache of their lives. The headache may be accompanied by nausea and vomiting. According to the National Institutes of Health, other potential symptoms include the following:

•Weakness or numbness in any part of the body

•Impaired speech

•Neck stiffness

•Double vision, loss of vision, or other sudden visual changes

•Drooping eyelids

•Confusion, lethargy, or other changes in mental status

•Seizures

If you notice these symptoms in yourself or a loved one, get medical help immediately. If an aneurysm has ruptured, every minute counts. Keep in mind, however, that the vast majority of headaches don't have anything to do with aneurysms.

While it's true that aneurysms that haven't ruptured usually don't cause symptoms, sometimes the bulging vessel announces itself by pressing against surrounding brain tissue. This can cause symptoms very similar to those of a rupture, including severe headaches, weakness or numbness on one side of the body, slurred speech, sudden changes in vision, and seizures. Again, don't take any chances. If you notice these symptoms, get medical help immediately.

When an aneurysm bursts, sealing off the rupture is the top priority. Typically, a brain surgeon will close off the base of the aneurysm with a clamp or sutures. This approach is generally very effective, but it's not suited for all patients. For one thing, surgeons have trouble reaching aneurysms that are deep in the brain. Also, according to Mayo Clinic, the surgery may be overly traumatic for patients who are weak or gravely ill.

In some cases, newer less invasive techniques may be appropriate. Doctors have developed a new approach for treating aneurysms. Instead of cutting open the skull, a doctor threads a thin catheter through an artery in the leg all the way up to the brain. The catheter releases tiny platinum coils that block the flow of blood to the aneurysm. (This procedure is usually done by an interventional neuroradiologist.)

Thanks to advances in CT scans and MRI, doctors are discovering more and more unruptured, asymptomatic aneurysms. Asymptomatic, unruptured aneurysms can be treated in much the same way as ruptured aneurysms. By clipping an aneurysm at its base or filling it with platinum coils, a doctor can greatly reduce the risk of a rupture. But according to the National Institutes of Health, nipping aneurysms in the bud often isn't a good idea.

If you have a small aneurysm and you've never had a rupture, treatment may be more dangerous than the aneurysm itself, according to the National Institute of Neurological Disorders and Stroke (part of the NIH). A small number of patients suffer a stroke or brain infection as a result of treatment. For this reason, low-risk aneurysms are often better left alone.

The decision to treat an asymptomatic, unruptured aneurysm also depends on a person's age and overall health. A young person with a moderately dangerous aneurysm may elect to receive treatment. But if the aneurysm is small, or if the patient is already in poor health, then the risks may outweigh the benefits.

Some aneurysms are much more likely than others to cause trouble. A study of more than 2,600 patients, published in the New England Journal of Medicine, found that small aneurysms (less than half an inch, or 10 millimeters across) almost always stayed intact -- especially if the patients had no history of ruptures. In contrast, about 6 percent of large aneurysms (more than one inch, or 25 millimeters across) burst within a year.

In short, not every unruptured aneurysm is a call for alarm. Your doctor can help you decide if the threat outweighs the risks of an operation. As with other serious conditions, it's always best to proceed with caution.

-- Chris Woolston, MS, is a health and medical writer with a master's degree in biology. He is a contributing editor at Consumer Health Interactive and was a staff writer at Hippocrates, a magazine for physicians. He has also covered science issues for Time Inc. Health, WebMD, and the Chronicle of Higher Education. His reporting on occupational health earned him an award from the northern California Society of Professional Journalists.

References

First published June 26, 2002
Last updated November 19, 2007
Copyright © 2002 Consumer Health Interactive

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