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Unruptured cranial aneurysms present dilemma.

SAN DIEGO -- What if 3-6 million Americans had an asymptomatic condition that was easily, but coincidentally, detected on CT and MRI scans?

What if a number of excellent, but expensive, options existed to treat this condition, potentially preventing a catastrophic event in 0%-53% of cases, depending on the size, location, and duration of the problematic entity?

Obviously, you would look to well-designed, prospective, randomized, controlled trials intended to determine which patients should be referred for treatment, which patients should be watched, and which should be reassured.

But such trials don't exist.

This real-life scenario describes asymptomatic, saccular, unruptured intracranial aneurysms (UIAs), which pose a management conundrum for virtually every neurologist in practice today.

"These are extremely common. About 2% of the population has a UIA," said Dr. Robert D. Brown during a symposium at the meeting.

Aneurysmal subarachnoid hemorrhages affect 6-10 per 100,000 U.S. population annually, with a case fatality rate of 30%-40%.

Still, "most aneurysms do not rupture," said Dr. Brown, chair of neurology at the Mayo Clinic in Rochester, Minn.

The predominance of natural history studies point to size as being of critical importance in the assessment of rupture risk, "no matter where the location or what the age of the patient," he said. Secondarily, location and age matter, with posterior aneurysms and those in older patients being at seemingly greater risk of rupture.

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But with smaller and smaller aneurysms becoming increasingly easy to see on scans, "'we're in the situation right now where the question is not 'Can we do anything [with incidentally discovered aneurysms in younger patients],' but should we?" he remarked.

Beyond patient age and aneurysm size and position, the hypothesized risk factors for rupture include smoking, hypertension, alcohol consumption (with risk associated with no alcohol or high alcohol use), and perhaps family history, as well as morphological characteristics and growth of the aneurysm itself over time.

Epidemiologic cohort studies can help to direct management in the absence of a well-designed, randomized trial, Dr. Brown said.

For example, data on unoperated patients who were enrolled in the 5,500patient ISUIA (International Study of Unruptured Intracranial Aneurysms) suggest that smaller aneurysms located in the anterior circulation of the circle of Willis and the cavernous segment of the internal carotid artery are quite unlikely to hemorrhage when they are followed conservatively for 5 years.

Available data from the trial also suggest that even very small (less than 7 ram) aneurysms have a potential for hemorrhage that is "noteworthy and certainly far from zero" if they are located in the posterior communicating artery or posterior circulation.

Current and future research is exploring whether more precise analysis of the features of such aneurysms--including their undulation and elliptical indices and nonspherical shape--may be more predictive of rupture risk.

Computational fluid dynamics, drawn from engineering principles, may also provide better guidance, Dr. Brown said.

In the meantime, he cited a "huge variation" in clinical practice when it comes to management of smaller, unruptured aneurysms, with some centers opting to treat 90% with coils or clips and others treating fewer than 10% of such cases.

His own practice, guided by the literature, is to advise treatment in the following situations:

* In younger patients in otherwise good health whose aneurysms measure 7 mm or greater.

* In younger patients in otherwise good health whose aneurysms measure less than 7 mm but are in the posterior circulation.

* Possibly, in older patients with aneurysms measuring 7-12 mm in the posterior circulation.

* In older patients with aneurysms greater than 12 mm in which a reasonable treatment option exists.

Dr. Brown advised aggressive treatment of hypertension and smoking-cessation management in all patients with unruptured aneurysms, as well as careful, imaging-based follow-up of conservatively managed patients based on limited data showing growth in moderate and large lesions over time.

Even 1 in 12 small (less than 8 ram) aneurysms demonstrated "clear, definitive growth" over 4 years in a study of 165 patients (Stroke 2009;40:406-11), he noted. Dr. Brown disclosed no conflicts of interest relative to his talk.

BY BETSY BATES

EXPERT ANALYSIS FROM THE ANNUAL MEETING OF THE AMERICAN NEUROLOGICAL ASSOCIATION
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Title Annotation:NEUROLOGIC DISORDERS
Author:Bates, Betsy
Publication:Family Practice News
Geographic Code:1USA
Date:Oct 15, 2011
Words:690
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