Deciding whether to treat an aneurysm

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Not all brain aneurysms that are discovered by chance will rupture (tear). But various factors increase the risk of a rupture, causing bleeding in the brain.

When a brain aneurysm is diagnosed, doctors try to determine the risk of complications. In other words, they try to find out how likely it is that the aneurysm will eventually burst and cause life-threatening bleeding in the brain.

This risk is higher if the aneurysm has particular characteristics or if you have certain other medical conditions. Habits like smoking can increase the risk too.

What increases the likelihood of a rupture?

The larger the aneurysm, the greater the risk of complications. There is no specific size at which “harmless” aneurysms become “dangerous.” But experts believe that aneurysms that are smaller than seven millimeters in diameter don't need to be treated at first, and can simply be monitored.

There's still a chance that small aneurysms will rupture, though. Because of this, other risk factors should be considered too when deciding whether or not to have treatment. For example, the risk of rupture is considered to be higher if an aneurysm

  • grows over time
  • is located in the brain arteries that supply the back part of the brain
  • has an irregular shape

The risk is also higher in patients who have more than one brain aneurysm – particularly if one of them has already bled. Experts think that additional examinations like special (MRI) scans can help to get an idea of how big the risk is. These scans can show how the blood in the aneurysm is flowing and how much it is pushing against the walls of the blood vessel.

Aside from the characteristics of the aneurysm itself, complications are more common in

  • people with high blood pressure,
  • people who smoke or drink a lot of alcohol,
  • women,
  • older people and
  • people with a family history of the disease – in other words, people who have a close relative such as a brother, sister or parent who has already had a ruptured aneurysm.

What can I do to lower my risk?

You can avoid or at least influence the following important risk factors:

  • High blood pressure
  • Smoking
  • Too much alcohol

You can do quite a bit to lower high blood pressure. Changing your diet, losing weight and getting more exercise can help. There are also effective medications for high blood pressure.

If you smoke, quitting can lower your risk of the aneurysm rupturing. Many smokers find this difficult to do. But various things can help you quit smoking.

The same applies to alcohol. If you want to drink less alcohol but not completely stop, try to drink only occasionally or only at special events. Depending on how much you drink, you may need professional help to quit.

Does the risk suggest that treatment is needed?

After a brain aneurysm is diagnosed, the main focus is on deciding whether the aneurysm needs to be treated. To make a decision, it's important to know how likely it is that the aneurysm will eventually rupture.

If the risk of bleeding in the brain is very low, treatment might cause more harm than good because it is associated with risks and side effects itself. On the other hand, treatment could prevent life-threatening bleeding in the brain in people who are at very high risk. For them, the benefits outweigh the possible side effects.

Whether an aneurysm will eventually rupture depends on many different factors. Also, the risk of bleeding in the brain must be weighed against the possible side effects and risks associated with the treatment. The treatment-related risks vary from person to person too. For all of these reasons, it's sometimes difficult to decide whether or not to have treatment. It's important to talk to doctors who specialize in the treatment of brain aneurysms.

A decision aid can help you prepare for doctor's appointments. For example, it can help you determine what is important to you and what you would like to know more about.

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IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Updated on September 29, 2021

Next planned update: 2024


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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