Unruptured intracranial aneurysms: appraisal of the literature and suggested recommendations for surgery, using evidence-based medicine criteria.

OBJECTIVE: The literature on unruptured intracranial aneurysms is reviewed, and an attempt is made to stratify it according to the weight of the evidence. Recommendations for surgery are suggested, using evidence-based criteria.
METHODS: A MEDLINE search was performed for 1966 to 1999. The focus was restricted to surgical management rather than other types of management, such as endovascular treatments. Each article was classified as Class I, II, or III according to the weight of the evidence. Some articles, such as literature reviews and data analyses, did not fit this classification and were grouped separately. Recommendations are based on the evidence available.
RESULTS: Forty-five articles were reviewed. Thirteen articles contained information on the natural history, 19 contained data on the risks of surgery, and 2 contained information on both. In addition, 11 contained analyses of costs and benefits. None met the criteria for Class I evidence. Seven articles on the natural history and 7 on the risks of surgery met the criteria for Class II evidence, and 6 and 12, respectively, met those for Class III evidence. The remainder of the articles were analyses or review articles.
CONCLUSION: There is insufficient evidence to recommend a standard of management. As a therapeutic guideline, conservative treatment is recommended for small aneurysms (<10 mm) and asymptomatic nongiant aneurysms in older people, whereas surgery is recommended for larger aneurysms in younger people and symptomatic aneurysms in fit patients. Other recommendations can be justified only as therapeutic options, using evidence-based criteria. Areas for future investigation are discussed.