Anatomic risk factors for middle cerebral artery aneurysm rupture: Computed tomography angiography study of 1009 consecutive patients

BACKGROUND: The middle cerebral artery (MCA) is the most frequent location for unruptured intracranial aneurysms. Controversy remains as to which unruptured MCA aneurysms should be treated prophylactically. OBJECTIVE: To identify independent topographical and morphological variables that could predict increased rupture risk of MCA aneurysms. METHODS: A retrospective analysis of computed tomography angiography data of 1009 consecutive patients with 1309 MCA aneurysms, referred between 2000 and 2009 to Helsinki University Hospital, was carried out. Morphological and topographical parameters examined for MCA aneurysms comprised aneurysm wall regularity, size, neck width, aspect ratio, bottleneck factor, height-width ratio, location along the MCA, side, distance from the internal carotid artery bifurcation, and dome projection in axial and coronal computed tomography angiography views. Univariate and multivariate logistic regression analyses were performed to determine independent risk factors for rupture. RESULTS: Of the 1309 MCA aneurysms, 69% were unruptured and 31% were ruptured. Most unruptured MCA aneurysms were smaller than 7 mm (78%), with a smooth wall (80%) and a height-width ratio of 1 (47%) and were located at the main bifurcation (57%). Ruptured MCA aneurysms, mostly 7 to 14 mm in size (55%), had an irregular wall (78%) and a height-width ratio greater than 1 (72%) and were located at the main bifurcation (77%). Thirty-eight percent of MCA bifurcation aneurysms, 74% of large aneurysms, 64% of aneurysms with an irregular wall, and 49% of aneurysms with a height-width ratio greater than 1 were ruptured. CONCLUSION: Location at the main MCA bifurcation, wall irregularity, and less spherical geometry were independently associated with rupture of MCA aneurysms with a correlation with aneurysm size. Copyright © 2013 by the Congress of Neurological Surgeons.