Incidental Saccular Aneurysms on Head MR Angiography: 5 Years' Experience at a Single Large-Volume Center

BACKGROUND AND PURPOSE: The diagnostic accuracy for unruptured intracranial aneurysms has increased, and incidental asymptomatic aneurysms have come to represent a substantial clinical burden because of their controversial natural history. However, their prevalence may be attributable to variations in evaluation methods and demographics. We therefore describe the prevalence and magnetic resonance angiography (MRA) findings of incidental intracranial saccular aneurysms over a 5-year period at a single large-volume center. METHODS: MRA images from 18,237 patients obtained between January 2001 and December 2005 were retrieved from the radiology report database. Patients diagnosed with incidental intracranial saccular aneurysms were identified and their MRA data were reviewed. Imaging and clinical follow-up data were evaluated. RESULTS: During the study period, 366 incidental intracranial saccular aneurysms were identified in 330 patients (prevalence, 1.8%; 95% confidence interval, 1.63%-2.01%; 115 men and 215 women; age range, 22-82 years; median age, 63 years). The prevalence was higher in women (215/8,112) than in men (115/10,125; P=0.02). The prevalence increased with age in women (P<0.01), but not in men (P=0.30). Aneurysm size ranged from 1.5 mm to 13 mm, with a median size of 4 mm. The most common location was the bifurcation of the middle cerebral artery (131/366; 35.8%). CONCLUSIONS: Our real world experience indicated a slightly lower overall prevalence of incidental intracranial saccular aneurysms than previously reported. The prevalence increased with age in women but not in men.