Incidence and risk factors for the growth of unruptured cerebral aneurysms: observation using serial computerized tomography angiography

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Object. The goal of this study was to examine the growth of unruptured intracranial aneurysms with the focus on the risk factors and incidence of these lesions.

Methods. One hundred sixty-six untreated cerebral saccular aneurysms were analyzed in 140 patients. The age of the patients ranged from 29 to 82 years (mean 62.8 years), the female/male ratio was 94:46, and the mean follow-up period was 17.7 months. Aneurysms were located at the internal carotid artery (ICA) in 68 patients, the middle cerebral artery (MCA) in 43, the anterior cerebral artery in 38, the basilar artery (BA) in 13, and the vertebral artery in four patients. The maximum diameter of the lesions ranged from 2 to 20 mm (mean 4.1 mm). All patients were examined using serial computerized tomography angiography to evaluate signs of aneurysm growth.

Although growth was identified in 10 aneurysms (nine patients [6.4%]), no bleeding occurred. Growth-related changes were significantly associated with the size of the aneurysm and occurred in three (2.4%) of 125 aneurysms measuring 2 to 4 mm, three (9.1%) of 33 lesions measuring 5 to 9 mm, and four (50%) of eight lesions measuring 10 to 20 mm. These changes were more frequently found in aneurysms located at the BA bifurcation (two [40%] of five lesions) and the ICA (six [8.8%] of 68 lesions) than in those located at the MCA (zero of 43 lesions, p < 0.05). The 1-, 2-, and 3-year cumulative growth rates calculated using the Kaplan—Meier method were 2.5, 8, and 17.6%, respectively.

Conclusions. A diameter of at least 10 mm and a location at the BA bifurcation or the ICA were significant risk factors for aneurysm growth. The incidence of growth was 2.5% in the 1st year and this risk increased yearly. Computerized tomography angiography is useful for follow up of patients with aneurysms because it allows the detection of even subtle morphological changes.

Article Information

Address reprint requests to: Hiromu Hadeishi, M.D., Ph.D., Department of Surgical Neurology, Research Institute for Brain and Blood Vessels—Akita, 6–10, Senshu-Kubota-machi, Akita, 0100874, Japan. email: hade@akita-noken.go.jp.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Case 1. Left: Initial CT angiogram (posteroanterior view) revealing the formation of a bleb on the top of the aneurysm dome. Right: Repeated CT angiogram obtained 6 months later clearly demonstrating another bleb in the dorsolateral aspect of the dome (arrow).

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    Case 2. Volume-rendered CT angiograms. Left: Control image demonstrating a BA bifurcation aneurysm (8 mm in maximum diameter; arrow) and an ICA—PCoA aneurysm (2 mm in maximum diameter). Right: Repeated CT angiogram obtained 4 years later depicting obvious enlargement of the BA bifurcation aneurysm (arrow) as well as of the ICA—PCoA aneurysm.

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    Graph showing the patient age distribution and aneurysm growth rate. The percentage of aneurysms exhibiting growth was highest among patients 60 to 79 years of age; however, this trend did not reach significance.

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    Graph showing the aneurysm size distribution and growth rates. The percentage of aneurysms exhibiting growth was significantly correlated with aneurysm size.

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    Graph showing the aneurysm site distribution and incidence of growth. The percentage of aneurysms exhibiting growth was significantly correlated with a location at the BA bifurcation (tip) or at the ICA when compared with the MCA.

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    Graph showing the results of the Kaplan—Meier analysis predicting the growth rate of unruptured aneurysms over a 4-year period. The vertical axis shows the percentage of aneurysms that did not exhibit any sign of growth.

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