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Multicenter Study
. 1998 Dec 10;339(24):1725-33.
doi: 10.1056/NEJM199812103392401.

Unruptured intracranial aneurysms--risk of rupture and risks of surgical intervention

International Study of Unruptured Intracranial Aneurysms Investigators
Free article
Multicenter Study

Unruptured intracranial aneurysms--risk of rupture and risks of surgical intervention

International Study of Unruptured Intracranial Aneurysms Investigators. N Engl J Med. .
Free article

Erratum in

  • N Engl J Med 1999 Mar 4;340(9):744

Abstract

Background: The management of unruptured intracranial aneurysms requires knowledge of the natural history of these lesions and the risks of repairing them.

Methods: A total of 2621 patients at 53 participating centers in the United States, Canada, and Europe were enrolled in the study, which had retrospective and prospective components. In the retrospective component, we assessed the natural history of unruptured intracranial aneurysms in 1449 patients with 1937 unruptured intracranial aneurysms; 727 of the patients had no history of subarachnoid hemorrhage from a different aneurysm (group 1), and 722 had a history of subarachnoid hemorrhage from a different aneurysm that had been repaired successfully (group 2). In the prospective component, we assessed treatment-related morbidity and mortality in 1172 patients with newly diagnosed unruptured intracranial aneurysms.

Results: In group 1, the cumulative rate of rupture of aneurysms that were less than 10 mm in diameter at diagnosis was less than 0.05 percent per year, and in group 2, the rate was approximately 11 times as high (0.5 percent per year). The rupture rate of aneurysms that were 10 mm or more in diameter was less than 1 percent per year in both groups, but in group 1, the rate was 6 percent the first year for giant aneurysms (> or =25 mm in diameter). The size and location of the aneurysm were independent predictors of rupture. The overall rate of surgery-related morbidity and mortality was 17.5 percent in group 1 and 13.6 percent in group 2 at 30 days and was 15.7 percent and 13.1 percent, respectively, at 1 year. Age independently predicted surgical outcome.

Conclusions: The likelihood of rupture of unruptured intracranial aneurysms that were less than 10 mm in diameter was exceedingly low among patients in group 1 and was substantially higher among those in group 2. The risk of morbidity and mortality related to surgery greatly exceeded the 7.5-year risk of rupture among patients in group 1 with unruptured intracranial aneurysms smaller than 10 mm in diameter.

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Comment in

  • Should intracranial aneurysms be treated before they rupture?
    Caplan LR. Caplan LR. N Engl J Med. 1998 Dec 10;339(24):1774-5. doi: 10.1056/NEJM199812103392409. N Engl J Med. 1998. PMID: 9845714 No abstract available.
  • Unruptured intracranial aneurysms.
    Berenstein A, Flamm ES, Kupersmith MJ. Berenstein A, et al. N Engl J Med. 1999 May 6;340(18):1439-40; author reply 1441-2. N Engl J Med. 1999. PMID: 10328707 No abstract available.
  • Unruptured intracranial aneurysms.
    Connolly ES Jr, Mohr JP, Solomon RA. Connolly ES Jr, et al. N Engl J Med. 1999 May 6;340(18):1440-1; author reply 1441-2. N Engl J Med. 1999. PMID: 10328708 No abstract available.
  • Unruptured intracranial aneurysms.
    Stieg PE, Friedlander R. Stieg PE, et al. N Engl J Med. 1999 May 6;340(18):1441; author reply 1441-2. N Engl J Med. 1999. PMID: 10328709 No abstract available.
  • Making the diagnosis of subarachnoid hemorrhage.
    Clatterbuck RE, Tamargo R, Rigamonti D. Clatterbuck RE, et al. N Engl J Med. 2000 May 11;342(19):1454-5; author reply 1455-6. doi: 10.1056/NEJM200005113421918. N Engl J Med. 2000. PMID: 10809622 No abstract available.

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