EVIDENCE-BASED ANSWER
The risk of rupture of a small cerebral aneurysm (<10 mm) is very low in asymptomatic patients who have never had a subarachnoid hemorrhage. Because the risk of morbidity and mortality from surgical intervention significantly exceeds that of nonsurgical monitoring for this group, primary care physicians do not need to refer patients with this condition to a neurosurgeon for clipping (strength of recommendation [SOR]: B, based on cohort and case-control studies). For patients managed conservatively, annual office follow-up and imaging evaluation should be considered, and is necessary if a specific symptom should arise (SOR: C, based on expert opinion).
Evidence summary
Intracranial aneurysms are not rare. Based on autopsy data, prevalence has been estimated to be 0.2% to 9.9% of the population.1 Ten to 15 million Americans may have unruptured intracranial aneurysms, most of which remain undiagnosed.2
Conditions leading to the diagnosis of unruptured intracranial aneurysms include:
- headache (in 36% of patients)
- ischemic cerebrovascular disease (17.6%)
- cranial nerve deficits (15.4 %)
- aneurysmal mass effect (5.7%)
- ill-defined “spells” (4.8%)
- convulsive disorder (4.2%)
- subdural or intracerebral hemorrhage (2.7%)
- brain tumor (1.7%)
- nervous system degenerative disease (0.5%).2
No randomized controlled trials have examined whether unruptured intracranial aneurysms should be treated surgically. In the absence of a clinical trial, the evidence to answer this question is based on observational, cohort, and case-control studies, where the risks of the natural history of the condition are weighed against the risks of surgical intervention.3
One study of the natural history of unruptured cerebral aneurysm included 130 patients with 161 unruptured intracranial aneurysms who were followed for a mean of 8.3 years.4,5 This prospective investigation found that 15 patients suffered an intracranial hemorrhage. There were no ruptures of the 102 aneurysms that were ≤10 mm in diameter at the time of discovery.4,5
In the largest cohort study to date, patients without a history of subarachnoid hemorrhage had an overall risk of rupture of 0.05% per year over 7.5 years. This study also found that surgery-related morbidity and mortality at 1 year among patients aged <45 years was 6.5%, compared with 14.4% for those aged 45 to 64 years, and 32% for those aged >64 years.2
Recommendations from others
The Stroke Council of the American Heart Association recommends that observation is generally appropriate for incidental, small (<10-mm) aneurysms in patients without previous subarachnoid hemorrhage. However, special consideration for treatment should be given to young patients in this group, small aneurysms approaching the 10-mm size, and aneurysms with daughter sac formation ( Figure). In addition, patients with a family history of aneurysm or aneurysmal subarachnoid hemorrhage deserve special consideration for treatment.
For patients managed conservatively, periodic follow-up imaging should be considered; imaging is necessary if a specific symptom should arise. If changes in aneurysmal size or configuration are observed, special consideration for treatment should be made.6
Aneurysm with daughter sac
CLINICAL COMMENTARY
Wail Malaty, MD
Mountain Area Health Education Center Hendersonville, NC
Department of Family Medicine, University of North Carolina Chapel Hill
Asymptomatic cerebral aneurysms are potentially disastrous, since rupture can result in permanent neurologic disability or death. The diagnosis causes anxiety and fear in many patients. I try to explain to them, in clear and simple language, the minimal risk of rupture if the aneurysm is observed vs the higher risk of surgical intervention. I allow patients to express their fear and anxiety. I also elicit their input into the decision to refer. If their fear and anxiety cannot be allayed, I will refer them to a neurosurgeon. I invite them to return after the referral to discuss any further course of action.