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(Stroke. 2009;40:406.)
© 2009 American Heart Association, Inc.

Original Contributions

Intracranial Aneurysm Enlargement on Serial Magnetic Resonance Angiography

Frequency and Risk Factors

Joseph D. Burns, MD; John Huston, III, MD; Kennith F. Layton, MD; David G. Piepgras, MD Robert D. Brown, Jr, MD

From the Departments of Neurology (J.D.B., R.D.B.), Diagnostic Radiology (J.H.), and Neurosurgery (D.G.P.), Mayo Clinic, Rochester, Minn; and the Department of Diagnostic Radiology (K.F.L.), Baylor University Medical Center, Dallas, Tex.

Correspondence to John Huston, III, MD, Department of Diagnostic Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail jhuston{at}mayo.edu

Background and Purpose— Size of an unruptured intracranial aneurysm (UIA) may be an important risk factor for rupture. Accordingly, serial noninvasive imaging is commonly used to assess untreated UIA for enlargement. Few data exist regarding the frequency and predictors of enlargement. We obtained this information from a group of patients followed with serial MR angiography (MRA).

Methods— We retrospectively identified 165 patients with 191 UIA followed with serial MRA. Fusiform aneurysms, UIA <2 mm, and UIA that were surgically or endovascularly treated before the first MRA were excluded. MRA was performed using 1.5-T and 3-T MRI. Maximal diameter was determined on MRA source images. Multivariate regression analysis was used to determine independent risk factors for growth.

Results— Twenty aneurysms (10%) grew over a median follow-up period of 47 months. Frequency of enlargement was 6.9%, 25%, and 83% for aneurysms <8 mm, 8 to 12 mm, and 13 mm, respectively (P<0.001 for trend). Of the variables we evaluated, original aneurysm diameter (OR, 1.28 per mm; 95% CI, 1.07 to 1.58) was the only independent predictor of enlargement. Aneurysms 8 mm in diameter were at highest risk for enlargement (OR, 7.25; 95% CI, 1.96 to 27.1). There was a trend toward increased risk of enlargement in patients with multiple aneurysms (OR, 2.50; 95% CI, 0.86 to 7.53).

Conclusions— Over a median follow-up period of 47 months, 10% of UIA enlarged. Larger aneurysms had a significantly increased risk of enlargement. The likelihood of enlargement was highest in aneurysms with diameters 8 mm. However, a clinically significant proportion of small aneurysms grow, and this growth can be detected by serial MRA.

Key Words: enlargement • magnetic resonance angiography • risk factors • unruptured intracranial aneurysm

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