Elsevier

The Lancet

Volume 362, Issue 9378, 12 July 2003, Pages 103-110
The Lancet

Articles
Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment

https://doi.org/10.1016/S0140-6736(03)13860-3Get rights and content

Summary

Background

The management of unruptured intracranial aneurysms is controversial. Investigators form the International study of Unrupted intracranial Aneurysms aimed to asses the natural history of unrupted Intracranial aneurysms and to measure the risk associalted with the repair.

Methods

Centres in the USA, Canada, and Europe enrolled patients for prospective assessment of unruptured aneurysms. Investigators recorded the natural history in patients who did not have surgery, and assessed morbidity and mortality associated with repair of unruptured aneurysms by either open surgery or endo-vascular procedures.

Findings

4060 patients were assessed-1692 did not have aneurysmal repair, 1917 had open surgery, and 451 had endovascular procedures. 5-year cumulative rupture rates for patients who did not have a history of subarachnoid haemorrhage with aneurysms located in internal carotid artery, anterior communicating or anterior cerebral artery, or middle cerebral artery were 0%, 2·6%, 14·5%, and 40% for aneurysms less than 7 mm, 7–12 mm, 13–24 mm, and 25 mm or greater, respectively, compared with rates of 2·5%, 14·5%, 18·4%, and 50%, respectively, for the same size categories involving posterior circulation and posterior communicating artery aneurysms. These rates were often equalled or exceeded by the risks associated with surgical or endovascular repair of comparable lesions. Patients' age was a strong predictor of surgical outcome, and the size and location of an aneurysm predict both surgical and endovascular outcomes.

Interpretation

Many factors are involved in management of patients with unruptured intracranial aneurysms. Site, size, and group specific risks of the natural history should be compared with site, size, and age-specific risks of repair for each patient.

Introduction

Unruptured intracranial aneurysms are diagnosed with greater frequency as imaging techniques improve. The management of unruptured intra-cranial aneurysms remains controversial because of incomplete and conflicting data about the natural history of these lesions and the risks associated with their repair.1, 2, 3, 4, 5, 6, 7, 8, 9

Results of phase 1 of this study have been reported pre-viously,1 and include a retrospective study of the natural history and a prospective assessment of morbidity and mortality associated with surgical repair of unruptured aneurysms. Here, we include only prospective data on the natural history of unruptured intracranial aneurysms, the clinical outcomes of endovascular treatment, and a more comprehensive assessment of the risks of surgical treatment. With these combined data, the study aim is to provide information about the magnitude and determinants of the risks associated with the natural history and repair of unruptured intracranial aneurysms.

Section snippets

Patients

Study coordinators identified eligible patients prospectively from people who were diagnosed between 1991 and 1998, and visited International Study of Unruptured Intracranial Aneurysms (ISUIA) centre. They used the system's central inpatient and outpatient admission records, and records from departments of radiology, neurosurgery, and neurology to identify eligible patients.

Patients were eligible for enrolment if they had at least one unruptured intracranial aneurysm, whether or not they had

Results

Between December, 1991, and December, 1998, 4060 patients were enrolled from 61 centres in the USA, Canada, and Europe. 2035 (50%) patients were identified before 1996; however, the accrual of cases was greatest in 1997 and 1998 when 1775 (43%) joined the study.

Table 1 shows the baseline characteristics of patients in the unoperated and operated cohorts. Conditions that led to the diagnosis of unruptured intracranial aneurysms did not differ substantially in the unoperated and operated cohorts (

Discussion

The idea that the natural history of unruptured intracranial aneurysms cannot be extrapolated from evaluation of patients with ruptured aneurysms is reinforced by the natural history data from this study. These data also indicate that aneurysm size (especially inpatients who have not had previous sub-arachnoid haemorrhage) and location have a significant role in determining the risk of future rupture. Early rupture rates in the prospective group were higher than in the previously published

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