ROCHESTER, Minn. -- An international study led by Mayo Clinic to be published in the July 12 issue of The Lancet provides new information about when unruptured brain aneurysms should and should not be treated.
The findings are from the International Study of Unruptured Intracranial Aneurysms (ISUIA), which involves 61 medical centers in the United States, Canada and Europe. This is the largest study of its kind and the first to follow up prospectively identified treated and untreated patients. The findings will help doctors provide advice about whether patients with brain aneurysms would be better off having brain surgery, undergoing an endovascular procedure or not repairing the aneurysm.
"If you have an unruptured aneurysm, your doctor now can better advise you about what to do," says David Wiebers, M.D., Mayo Clinic neurologist and the study's principal investigator. "Some of them can be left alone, and others are better to repair, depending on the situation. We're more sophisticated in what we can say about the magnitude of the risks of treatment and non-treatment, and the predictors of risk on either side."
In this study involving 4,060 patients with unruptured brain aneurysms, 1,917 underwent surgical repair of the aneurysm; 451 were treated with an endovascular coiling procedure designed to shut off blood flow to an aneurysm by producing clot within it; and 1,692 patients did not undergo repair of the aneurysm. Patients were followed prospectively for up to nine years. The researchers found that aneurysm size corresponded to rupture rate and observed that patients with aneurysms smaller than seven millimeters were at low risk for rupture (approximately 0.1 percent risk per year). They also found that history of rupture due to another aneurysm and aneurysm location affected rupture rates. Aneurysms toward the front of the brain were less risky than those in the back. Additionally, researchers learned that age is a key factor in the success of surgery, with risks increasing substantially at age 50 and older, and increasing even more after age 60 or 70. Aneurysm size and location influenced both the outcomes of surgery and endovascular coiling.
The new information will help physicians counsel their patients in an emotionally trying time, according to the ISUIA investigators.
"Patients who have unruptured brain aneurysms believe that they have a bomb in their heads ready to burst," says Allan Fox, M.D., neuroradiologist at Sunnybrook & Women's College Health Sciences Centre, Toronto. "They want to stop it. They need advice about the need for treatment and the risks of treatment versus no treatment."
Richard Kerr, M.D., a neurosurgeon at the Radcliffe Infirmary in Oxford, England, concurs. "They live normal lives, have families, and hold down jobs, and suddenly they have to make a decision. It does result in a significant amount of stress for those patients," he says.
The new findings do not justify a rush to the operating room for most aneurysms, according to the researchers.
"Unruptured aneurysms are relatively common in the population and are discovered more and more frequently as incidental findings as our imaging technologies improve," says Dr. Wiebers. "The discovery of an unruptured brain aneurysm need not be the cause for panic or undue alarm. They are not necessarily ticking time bombs as some have suggested. In fact, some of them have such a low risk of rupture that they are better left untreated. In situations where it is advisable to treat unruptured aneurysms, more treatment options are available than in the past, and the quality of these treatments continues to improve over time."
This study indicates that in addition to size, the aneurysm's location, a history of bleeding from a separate aneurysm and the patient's age are key factors to consider.
Dr. Kerr says deciding whether or not to treat a patient's aneurysm is a process of collecting all the information that you can, and then sitting down with the patient and relatives and reviewing the pros and cons of the treatment options and nontreatment.
"The more information I have, the more information I can give to the patient," says Dr. Kerr. "At the end of the day, the thing that sways patients most of all is their ability to live with the problem. Some patients can go away and forget it. Other patients never rest knowing that they've got the problem there."
The investigators emphasize that physicians cannot make blanket treatment recommendations for all patients with aneurysms.
"The management of any individual patient with an aneurysm has to be customized to its site, size, the patient's age and general well-being, and local factors like who's available to deal with it for them," says Dr. Kerr. "For some unruptured aneurysms, the risks of treatment are higher than leaving them alone."
In many cases, small aneurysms are detected "by accident." In other words, oftentimes these patients may be completely asymptomatic, going through their life activities feeling completely well. Then the patient has, say, a bicycle accident, and is given a CT scan at the hospital. The scan comes back showing an aneurysm in the person's brain. Thus, the patient and the doctor are faced with a quandary.
According to Dr. Wiebers, the information from this new study can be helpful to patients and their physicians as they face such a dilemma.
"It's a major issue, because between 2 percent and 6 percent of the population have or will have intracranial aneurysms," says Dr. Wiebers. "Although epidemiological data suggest that most aneurysms don't rupture, you need to figure out which ones will."
Dr. Kerr agrees that this issue touches many people, if indirectly. "I suspect that most people would know of someone or have heard of someone with a hemorrhage," he says. "I doubt they'd know it was due to an aneurysm. I think more people would be aware of someone who has had a stroke, and a significant proportion of those would be due to an aneurysm."
The rupture of an aneurysm is serious.
"A rupture creates a subarachnoid hemorrhage," says Dr. Wiebers. "There is a 30 percent to 50 percent chance you'll die within 30 days. One-half of those who survive will end up disabled."
Ultimately, the decision about what to do with an aneurysm lies with the patient.
"In some cases, it comes down to a largely philosophical choice, particularly when the risks are relatively balanced between treatment and nontreatment," says Dr. Wiebers. "We always need to listen to what's on that patient's mind and what they prefer as they weigh the scientific information we can provide about risks."
Physicians involved in this project are optimistic about how the findings of this study will allow them to advise their patients.
"The most important thing is that we've taken a group of patients who harbor potentially lethal aneurysms and followed them to determine the natural history of aneurysms to try to identify which group of patients should be worried," says Dr. Kerr. "I hope this will help patients feel better informed and more confident in making a decision."
The study's investigators desire the research to continue.
"We're getting more information all the time about relative risks to these patients," says Dr. Kerr. "I hope that this study doesn't stop here. The longer we follow these patients … the more information we can get from them … the more we can give to new patients about their risks."
Dr. Fox agrees that further research is warranted, especially for the newer treatment: endovascular coiling. "The new ISUIA information is a big step forward. Further study is needed for unruptured aneurysms; however, more study is warranted particularly for the long-term effects of endovascular coiling, including improved efficacy and unknown additional risks from the newer devices," he says.
An intracranial aneurysm occurs when a weak spot on the wall of an artery in the brain balloons out, forming a sac that fills with blood. When an intracranial aneurysm ruptures, it releases blood into the spaces around and sometimes into the brain causing a hemorrhagic stroke. Although hemorrhagic strokes account for only about 20 percent of all strokes, they cause nearly one-half of stroke deaths. Specifically, subarachnoid hemorrhages (bleeding under the outer membrane around the brain) can lead to extensive brain damage and are the deadliest of strokes.
For further information on the ISUIA study, including a list of study sites, please see http://mayoresearch.mayo.edu/mayo/research/ISUIA/
This study was sponsored by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health, located in Bethesda, MD.
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