Medical Edge Newspaper Column

Brain Aneurysm Diagnosis May Not Require Treatment

January 23, 2009
Dear Mayo Clinic:
I was just diagnosed with a brain aneurysm and feel like I have a time bomb in my head. My doctor says I don't have to worry. Shouldn't I get it repaired right away?

Answer:
It's understandable that you're frightened by the thought of having an aneurysm in your head. But research has shown that depending on size, location and other factors, some brain aneurysms don't require treatment. Instead, they can be monitored, and the risk of rupture is quite low.

A brain aneurysm, also known as an intracranial or cerebral aneurysm, is an abnormal sac or tiny balloon on a blood vessel in the brain. Some aneurysms may rupture and bleed into the area between the brain and the surrounding membrane, leading to a type of stroke called a subarachnoid hemorrhage, or even death. An estimated 2 percent of Americans — approximately 6 million people — have brain aneurysms. Aneurysms rupture in only about 25,000 people each year, about 35% of whom die as a result. This indicates that most aneurysms do not rupture.

A recent international research study led by Mayo Clinic followed more than 4,000 people with unruptured brain aneurysms for nine years. The study's findings, released in 2008, showed that rupture risk was somewhat higher among patients with aneurysms in the back of the brain (the vertebral or basilar arteries), or in the posterior communicating artery, compared to those whose aneurysms were in the front of the brain.

Patients whose aneurysms were more than 12 millimeters (mm) in diameter were at least twice as likely to experience rupture, compared to those whose aneurysms were 7 to 12 mm. Those with aneurysms less than 7 mm that were located in the front of the brain had an extremely low rupture rate — less than 1/2 of 1 percent per year.

Patients with a previous history of a ruptured brain aneurysm had an increased risk of a new aneurysm rupturing, particularly with small aneurysms.

When considering treatment, a person's overall health also should be taken into account. Family history should be reviewed, because some studies suggest that a family history of brain aneurysm rupture may increase a patient's risk of rupture of a previously unruptured aneurysm.

This information can help you and your doctor weigh the risks and benefits of treating versus monitoring a brain aneurysm.

Two standard treatment options are used for a brain aneurysm. The first is microvascular clipping. During this procedure, a neurosurgeon removes a small section of the skull to access the aneurysm. The surgeon then locates the blood vessel that feeds the aneurysm, and places a tiny metal clip on the neck of the aneurysm to stop blood flow into it.

The second option is endovascular embolization, a less invasive alternative to surgical clipping. The doctor inserts a hollow plastic tube (catheter) into an artery, usually in the groin, and threads it through the body to the aneurysm. The doctor then pushes a spiral of soft platinum wire through the catheter and into the aneurysm. The wire coils up inside the aneurysm, reducing 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 repeat procedures may be necessary, particularly for larger aneurysms. The surgical clip procedure may be a better choice for people who have larger or more complicated aneurysms. The risk of surgery increases in people over age 50.

For those with a smaller aneurysm, particularly in the front of the brain, the risk of rupture may be less than the risk associated with treatment. In many cases, the aneurysm can be left alone and monitored with periodic computerized tomography angiography or magnetic resonance angiography to see if the aneurysm enlarges, suggesting that treatment may need to be considered.

High blood pressure, if present, should be aggressively treated, and those who smoke cigarettes should be encouraged to quit. Both issues can lead to aneurysm formation and rupture.

Talk to your doctor about the size and location of your brain aneurysm, as well as other factors that may influence the risk of rupture. Based on that information, discuss the risks of treatment compared to long-term monitoring.

— Robert D. Brown Jr., M.D., Neurology, Mayo Clinic, Rochester, Minn.