CFP
HOME HELP CONTACT US FEEDBACK SUBSCRIPTIONS CURRENT ISSUE PAST ISSUES SEARCH
QUICK SEARCH:   [advanced]


     

Can Fam Physician
Vol. 54, No. 11, November 2008, pp.1535 - 1538
Copyright © 2008 by The College of Family Physicians of Canada
This Article
Right arrow Abstract Freely available
Right arrow Résumé
Right arrow Full Text (PDF)
Right arrow Rapid Responses: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when Rapid Responses are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Lysack, J. T.
Right arrow Articles by Coakley, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lysack, J. T.
Right arrow Articles by Coakley, A.

Clinical Review

Asymptomatic unruptured intracranial aneurysms

Approach to screening and treatment

John T. Lysack, MD FRCPC
Assistant Professor of Radiology and Clinical Neurosciences at the University of Calgary in Alberta and is a neuroradiologist based at the Foothills Medical Centre in Calgary

Annalee Coakley, MD CCFP
Family physician in Calgary, Alta

Correspondence: Dr John T. Lysack, Diagnostic Imaging, Foothills Medical Centre, 1403-29 St NW, Calgary AB T2N 2T9; e-mailjohn.lysack{at}gmail.com

Brain imaging, for a variety of reasons, is being performed more frequently in Canada. As a result, an increasing number of asymptomatic unruptured intracranial aneurysms (AUIAs) are being discovered, either on purpose (ie, via screening) or as an incidental finding (ie, incidentaloma). As more aneurysms are discovered, family physicians can expect to be further involved in their management.

For screening to be considered effective, the screened population must have a better outcome than the unscreened population. Differences in outcome between screened and unscreened populations are primarily a reflection of the risks related to diagnosis and treatment versus the natural history of the condition. Similarly, differences in outcome between patients with treated and conservatively managed incidentalomas are a reflection of the risks related to treatment versus the natural history of the condition. In other words, the natural history of a lesion must be sufficiently poor to justify the risks of intervention.

Case 1

Ms A. is a 45-year-old woman who has recently moved to the city and presents to her new family physician for an initial visit. She is in good health, but during a routine review of her family history it is revealed that her father died of a ruptured intracranial aneurysm. She is unaware of any other family history of intracranial aneurysm. She is asymptomatic and in good health. Should Ms A. be screened for an intracranial aneurysm?

Case 2

Ms B. is a 45-year-old woman who was struck in the face by a softball during a recreational game. She reported to the local emergency department for management of a laceration. In case of underlying injury, a computed tomography scan of the head and facial bones was performed. There was no fracture or intracranial hemorrhage; however, focal prominence of the left middle cerebral artery (MCA) raised the possibility of an incidental unruptured intracranial aneurysm. A computed tomography angiogram was performed, which confirmed the presence of a 3-mm saccular aneurysm at the left MCA bifurcation. Does this aneurysm require treatment?

Case 3

Ms C. is a 45-year-old woman who comes to her family physician for follow-up of an incidentally discovered 3-mm left MCA bifurcation aneurysm. Although she remains asymptomatic, she has been researching her condition on the Internet and is now considering prophylactic treatment. She has heard that coiling is better than clipping. Is that true?

Sources of information

PubMed was searched using the phrase unruptured intracranial aneurysm. Results were limited to human studies published in the English language from January 1995 to January 2008. Relevant papers were selected for review. Additional articles were identified from the reference lists of relevant papers. Scientific statements of the Stroke Council of the American Heart Association that pertained to intracranial aneurysms were also reviewed.

Main message

When intracranial aneurysms rupture the results are devastating; half of patients die and up to half of those who survive are disabled.1 Fortunately, although the prevalence of intracranial aneurysms in the general population is relatively high (2%),2 the incidence of subarachnoid hemorrhage (SAH) in the general population is relatively low (6 to 9 cases per 100 000 person-years).3,4 This implies that most intracranial aneurysms never rupture.

The best estimate of the rupture risk of intracranial aneurysms is arguably from a recent meta-analysis,5 which yielded an annual rupture risk of 0.6% to 1.3%. Subgroup analyses showed that asymptomatic aneurysms were 4 to 5 times less likely to rupture than symptomatic aneurysms; small aneurysms (≤ 5 mm) were 2 to 3 times less likely to rupture than larger (> 5 mm) aneurysms; and anterior circulation aneurysms were 2 to 3 times less likely to rupture than posterior circulation aneurysms (those involving the vertebrobasilar system or posterior cerebral arteries).5 An earlier study suggested that the annual rupture risk for small aneurysms (< 10 mm) might be as low as 0.05%, although this claim is controversial.6

Patients with a family history of aneurysmal SAH are at increased risk of harbouring an intracranial aneurysm compared with the general population. Epidemiologic studies have shown that patients with a single first-degree relative with aneurysmal SAH have a 3% to 6% risk of harbouring AUIAs (twice the baseline risk of the general population),7,8 while patients with 2 or more first-degree relatives with aneurysmal SAH have an 8% to 10% risk of harbouring AUIAs (4 to 5 times the baseline risk of the general population).8,9

In deciding whether or not to intervene, the risk of intervention (ie, treatment-related mortality and morbidity) must be weighed against the risk of nonintervention (ie, risk of rupture). Treatment-related risks are substantial. In a recent, large retrospective study (2535 cases from 18 American states), 11.5% of patients had an adverse outcome following elective treatment of their unruptured intracranial aneurysm and 53 patients (2.1%) died.10 A prospective study of the risks and benefits of screening for intracranial aneurysms in first-degree relatives of patients with sporadic SAH showed that although screening resulted in a small increase in life expectancy (4 weeks per person screened), this was overshadowed by a substantial decrease in quality of life (19 years of decreased function per person screened).7 The study also showed that in order to prevent 1 SAH, 149 first-degree relatives would need to be screened; to prevent 1 fatal SAH, 298 would need to be screened. From a societal perspective, the cost-effectiveness of various management strategies is also of interest. In a recent comprehensive cost-effectiveness analysis,11 conservative management (no treatment) was the only cost-effective strategy for small (< 7 mm) intracranial aneurysms (using an incremental cost-effectiveness ratio threshold of $100 000 per quality-adjusted life-year).

Given the relatively high risks of treatment and the comparatively modest anticipated benefits, the Stroke Council of the American Heart Association has concluded that screening for AUIAs in the general population is not indicated.12 Despite increased risk of harboured AUIAs, screening patients with a single first-degree relative with aneurysmal SAH is also not generally recommended.12 Screening patients with 2 or more first-degree relatives with aneurysmal SAH is controversial—although this population is at a substantially greater risk of harbouring AUIAs, the effectiveness of screening has not been studied and therefore remains unknown.12 Treatment is not generally advocated in patients with small (< 10 mm) asymptomatic intracranial aneurysms in patients without a personal history of SAH.12

The prospective, randomized International Subarachnoid Aneurysm Trial (ISAT)13 showed that endovascular coiling of ruptured intracranial aneurysms was associated with improved outcomes when compared with surgical clipping (24% versus 31% morbidity or severe disability at 1 year). Although not as rigorously studied, coiling of unruptured intracranial aneurysms might improve short-term outcomes as well. In a recent nonrandomized retrospective study,10 adverse outcomes at discharge following endovascular treatment of unruptured intracranial aneurysms were less frequent than those following surgical treatment (7% versus 13%), and in-hospital mortality rates were lower (0.9% versus 2.5%).

Because coiling is a relatively new technique, however, its long-term outcomes are not yet known. Questions remain about the durability of endovascular repair. For example, follow-up with the ISAT13 study population has shown that retreatment occurs almost 7 times more frequently for coiled aneurysms than for clipped aneurysms.14

Case resolutions

Based on the evidence presented, the cases should be resolved as follows:

Case 1
Ms A. does not need to be screened for an intracranial aneurysm. Given the relatively high risks of treatment and the modest anticipated benefits, screening for AUIAs in patients with a single first-degree relative with a ruptured intracranial aneurysm is not generally recommended (level II evidence).

Case 2
Ms B.’s aneurysm does not need to be treated. The risks of treatment might be greater than the risk of rupture for her small (≤ 5 mm) AUIA (level II evidence). Endovascular coiling or surgical clipping of larger aneurysms should be considered on a case-by-case basis. Consultation with an interventional neuroradiologist or neurosurgeon should be considered for patients with AUIAs larger than 5 mm (level III evidence).

Case 3
Ms C. might be correct that coiling is better than clipping. There is some evidence that short-term outcomes are better with coiling than with clipping (level II evidence), but whether or not long-term outcomes are similar has yet to be determined.

Conclusion

The optimal management of patients with AUIAs is controversial. There is currently a lack of good scientific evidence to support surgical or endovascular treatment of unruptured intracranial aneurysms.15 Screening is therefore difficult to justify at the present time. In the absence of a randomized controlled trial of intervention versus observation, management decisions are currently made based on estimations of natural history versus expected treatment outcomes (level III evidence). A prospective randomized controlled trial (Trial on Endovascular Aneurysm Management, known as the TEAM study)16 is now under way to address this issue. It is expected to conclude in 2021.

Levels of evidence

Level I: At least one properly conducted randomized controlled trial, systematic review, or meta-analysis

Level II: Other comparison trials, non-randomized, cohort, case-control, or epidemiologic studies, and preferably more than one study

Level III: Expert opinion or consensus statements


EDITOR’S KEY POINTS

  • Brain imaging is being performed more frequently in Canada and, as a result, an increasing number of asymptomatic unruptured intracranial aneurysms (AUIAs) are being discovered. How should such AUIAs be managed?
  • While ruptured intracranial aneurysms are devastating—half of patients die and up to half of those who survive are disabled—most intracranial aneurysms never rupture. Management decisions are currently made based on estimations of natural history versus expected treatment outcomes. Treatment-related risks are substantial, and there is currently insufficient evidence to support surgical or endovascular treatment of AUIAs in most cases.
  • Should the natural history of a lesion be estimated to be sufficiently poor to justify the risks of intervention, some evidence suggests that endovascular coiling of unruptured intracranial aneurysms might improve outcomes compared with surgical clipping. Because coiling is a relatively new technique, however, its long-term outcomes are not yet known and questions remain about the durability of endovascular repair.

 


POINTS DE REPÈRE DU RÉDACTEUR

  • Comme l’imagerie cérébrale est utilisée de plus en plus souvent au Canada, un nombre croissant d’anévrysmes intra-crâniens non rompus asymptomatiques (AINA) sont découverts. Comment doit-on traiter ces AINA?
  • Alors que la rupture d’un anévrysme intracrânien est désastreuse—la moitié des patients meurent et plus de la moitié des survivants sont handicapés—la plupart de ces lésions ne se rompent jamais. À l’heure actuelle, la décision de traiter tient compte de l’évolution naturelle prévue de l’anévrysme par rapport aux résultats escomptés du traitement. Les traitements comportent des risques importants et il n’y a actuellement pas de preuves suffisantes pour justifier un traitement chirurgical ou endovasculaire dans la majorité des cas d’AINA.
  • Pour les anévrysmes dont l’évolution naturelle est suffisamment inquiétante pour justifier le risque d’une intervention, certaines données suggèrent que l’insertion d’un coil dans un anévrysme intracrânien non rompu pourrait avoir une meilleure issue qu’un clampage chirurgical. Toutefois, comme l’insertion du coil est une technique relativement nouvelle, ses résultats à long terme ne sont pas encore connus, et on ignore toujours la durabilité de cette intervention.

 

Footnotes

Contributors

Drs Lysack and Coakley contributed to the concept of the article, the literature search, the review of selected articles, and preparing the manuscript for submission.

Competing interests

None declared

Cet article a fait l’objet d’une révision par des pairs.

This article has been peer reviewed.

References

  1. Hop JW, Rinkel GJ, Algra A, van Gijn J. Case-fatality rates and functional outcome after subarachnoid hemorrhage: a systematic review. Stroke 1997;28(3):660–4.[Abstract/Free Full Text]
  2. Rinkel GJ, Djibuti M, Algra A, van Gijn J. Prevalence and risk of rupture of intracranial aneurysms: a systematic review. Stroke 1998;29(1):251–6.[Abstract/Free Full Text]
  3. De Rooij NK, Linn FH, van der Plas JA, Algra A, Rinkel GJ. Incidence of subarachnoid haemorrhage: a systematic review with emphasis on region, age, gender and time trends. J Neurol Neurosurg Psychiatry 2007;78(12):1365–72.[Abstract/Free Full Text]
  4. Linn FH, Rinkel GJ, Algra A, van Gijn J. Incidence of subarachnoid hemorrhage: role of region, year, and rate of computed tomography: a meta-analysis. Stroke 1996;27(4):625–9.[Abstract/Free Full Text]
  5. Wermer MJ, van der Schaaf IC, Algra A, Rinkel GJ. Risk of rupture of unruptured intracranial aneurysms in relation to patient and aneurysm characteristics: an updated meta-analysis. Stroke 2007;38(4):1404–10.[Abstract/Free Full Text]
  6. International Study of Unruptured Intracranial Aneurysms Investigators. Unruptured intracranial aneurysms—risk of rupture and risks of surgical intervention. N Engl J Med 1998;339(24):1725–33.[Abstract/Free Full Text]
  7. Magnetic Resonance Angiography in Relatives of Patients with Subarachnoid Hemorrhage Study Group. Risks and benefits of screening for intracranial aneurysms in first-degree relatives of patients with sporadic subarachnoid hemorrhage. N Engl J Med 1999;341(18):1344–50.[Abstract/Free Full Text]
  8. Ronkainen A, Miettinen H, Karkola K, Papinaho S, Vanninen R, Puranen M, et al. Risk of harboring an unruptured intracranial aneurysm. Stroke 1998;29(2):359–62.[Abstract/Free Full Text]
  9. Raaymakers TW, Rinkel GJ, Ramos LM. Initial and follow-up screening for aneurysms in families with familial subarachnoid hemorrhage. Neurology 1998;51(4):1125–30.[Abstract/Free Full Text]
  10. Higashida RT, Lahue BJ, Torbey MT, Hopkins LN, Leip E, Hanley DF. Treatment of unruptured intracranial aneurysms: a nationwide assessment of effectiveness. AJNR Am J Neuroradiol 2007;28(1):146–51.[Abstract/Free Full Text]
  11. Takao H, Nojo T. Treatment of unruptured intracranial aneurysms: decision and cost-effectiveness analysis. Radiology 2007;244(3):755–66.[Abstract/Free Full Text]
  12. Bederson JB, Awad IA, Wiebers DO, Piepgras D, Haley EC Jr, Brott T, et al. Recommendations for the management of patients with unruptured intracranial aneurysms: a statement for healthcare professionals from the Stroke Council of the American Heart Association. Stroke 2000;31(11):2742–50.[Free Full Text]
  13. Molyneux AJ, Kerr RS, Yu LM, Clarke M, Sneade M, Yarnold JA, et al. International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion. Lancet 2005;366(9488):809–17.[Medline]
  14. Campi A, Ramzi N, Molyneux AJ, Summers PE, Kerr RS, Sneade M, et al. Retreatment of ruptured cerebral aneurysms in patients randomized by coiling or clipping in the International Subarachnoid Aneurysm Trial (ISAT). Stroke 2007;38(5):1538–44. Epub 2007 Mar 29.[Abstract/Free Full Text]
  15. Raymond J, Meder JF, Molyneux AJ, Fox AJ, Johnston SC, Collet JP, et al. Unruptured intracranial aneurysms: the unreliability of clinical judgment, the necessity for evidence, and reasons to participate in a randomized trial. J Neuroradiol 2006;33(4):211–9.[Medline]
  16. TeamStudy.org [homepage on the Internet], Montreal, QC: TEAM Study; 2008. Available from: www.teamstudy.org. Accessed 2008 Sep 25.




This Article
Right arrow Abstract Freely available
Right arrow Résumé
Right arrow Full Text (PDF)
Right arrow Rapid Responses: Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when Rapid Responses are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Lysack, J. T.
Right arrow Articles by Coakley, A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lysack, J. T.
Right arrow Articles by Coakley, A.

HOME HELP CONTACT US FEEDBACK SUBSCRIPTIONS CURRENT ISSUE PAST ISSUES SEARCH