New Consensus on Unruptured Intracranial Aneurysm

April 02, 2014

Many factors other than size and location must be considered in deciding whether to repair an unruptured intracranial aneurysm, according to a new consensus paper on the subject.

The paper, published online in Stroke on March 25, was collated by 39 major opinion leaders in the field.

"The natural history of unruptured intracranial aneurysms remains uncertain and especially indications for prophylactic aneurysm repair are somewhat controversial," cerebrovascular surgeon and lead author Nima Etminan, MD, Department of Neurosurgery, Medical Faculty Heinrich-Heine-University, Düsseldorf, Germany, explained to Medscape Medical News.

"There is an increasing need to reliably counsel patients with unruptured aneurysms on the best course of action," he said. "To address this, we convened a large group of internationally renowned cerebrovascular experts from different countries and fields to form a consensus on factors that need to be taken into account when making such decisions."

They used the Delphi consensus method, in which experts in the field are asked to define which factors they believe to be relevant; the various factors were then rated for their individual importance regarding the assessment of a patient with an unruptured aneurysm.

A "Comprehensive Guide for Doctors"

Dr. Etminan said, "This gives the reader a good impression on current opinion on the assessment of aneurysms, especially what factors cerebrovascular specialists consider to increase risk of rupture or risk of treatment and where areas of uncertainty are. It may serve as a comprehensive guide for doctors as to what to take into account, and what future studies should investigate."

He acknowledged that this approach does have the limitation in that it is based on expert opinion rather than hard evidence. "Opinion is not the same thing as evidence. But when unbiased evidence is somewhat lacking, expert opinion has to be used to formulate guidance on such controversial topics," he commented.

He pointed out that because patients are undergoing cranial imaging more frequently for symptoms such as headache and dizziness, unruptured intracranial aneurysms, which occur in about 2% to 3% of the population, are being found more often. They are usually small and asymptomatic.

He noted that many less specialized physicians frequently consider 2 main features of an unruptured aneurysm when deciding on repair: size and location. One of the largest prospective studies to evaluate the risk for rupture previously found that aneurysms less than 7 mm in diameter have a very low risk for rupture. As a result, some physicians have considered this as a specific threshold used to make decisions on repair.

However, small aneurysms are often found as a cause in the setting of subarachnoid hemorrhage (SAH), so additional factors might put an aneurysm at risk for rupture. Some of these factors are clear and others continue to be studied.

"Our consensus shows that cerebrovascular specialists consider many factors when making a decision regarding the best management approach. The cerebral vasculature and, moreover, cerebral aneurysms are a complex biological system. It cannot just be reduced to size and location," Dr. Etminan commented.

The following major factors were identified:

  • patient age and life expectancy;

  • comorbid diseases;

  • risk factors (previous subarachnoid hemorrhage from a different aneurysm, family history of unruptured intracranial aneurysm, or SAH and nicotine use);

  • aneurysm location, size, and morphology (lobulation/irregularity);

  • aneurysm growth or de novo formation on serial imaging;

  • clinical symptoms (cranial nerve deficit, mass effect, and thromboembolic events); and

  • risk factors for treatment.

On the importance of life expectancy, Dr. Etminan explained that while the risk for rupture for some aneurysms may be low over a 5- to 10-year period, it will be difficult to estimate this risk over a 30- to 40-year period. Thus, a younger patient will have a higher lifetime risk for rupture and is therefore a higher priority for repair. Similarly, patients with comorbid conditions that may limit their life may be a lower priority.

"Basically we are advising clinicians that factors beyond aneurysm size and location should be considered in making a decision, and even some small aneurysms require consideration of aneurysm repair. If I had a young patient who was a smoker and had hypertension and a 4-mm aneurysm, my advice may be different than if it was a 75-year-old patient who didn't have those risk factors and aneurysm of the same size."

On the assessment of aneurysm growth, Dr. Etminan noted that this was a highly problematic area. "This needs to be assessed by serial imaging, but the problem is that aneurysms are not assumed to grow in a linear way. Rather, they may grow in an episodic manner — at least some aneurysms seem to have growth spurts and then periods of stability. Growth is a sign of instability, but we don't know if we're monitoring it over a period of growth or not."

Dr. Etminan believes that every patient with an aneurysm should have a full evaluation, with all these factors considered.

"If an aneurysm is detected on a scan we advise the clinician to refer the patient to a cerebrovascular specialist who can make an informed decision with the patient on the way forward. The many different risk factors discussed in this paper should be taken into account. The estimation of the natural history of an unruptured aneurysm is far more complicated than just taking a quick look at size and location."

Scores in Development

On the basis of the consensus reached in this paper, the authors have developed a preliminary score — known as the Unruptured Intracranial Aneurysm Treatment Score (UIATS) — described in a presentation at the recent American Heart Association/American Stroke Association International Stroke Conference in San Diego, California. Dr. Etminan emphasized the early nature of the score.

"There is still a lot we don't know," he said, "and it is hard to account accurately for many of the factors that we do know about, such as life expectancy. We have validated the first version of the score but it will need further validation."

Another score for evaluating unruptured aneurysms — the PHASES score — has also been reported recently. Dr. Etminan explained that the PHASES score is based on a meta-analysis of various prospective observational studies. The overall predictive value of the score is unclear because of some potential patient selection bias in the included studies and also different definitions for outcome measures, which limit the ability to pool all the data. "The difference is that PHASES basically reflects well the existing evidence, but mainly based on the most common data elements between these studies, and if validated, the UIATS system will include numerous additional factors that could not be accounted for in PHASES. The principal investigators of the underlying trials are part of our panel to develop and validate the UIATS system," he added.

Stroke. Published online March 25, 2014. Abstract

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