Introduction: It is believed that arterial branching is governed by the principle of total minimum work (1) and prior studies have shown that cerebral vasculature generally adheres to this optimality principle (2). Bifurcation angles of cerebral arteries impact local blood flow and wall shear stress and these hemodynamic characteristics may play a role in aneurysmal development and subsequent rupture (2-3). Thus, further understanding of these quantitative parameters is necessary to assess aneurysmal rupture status (2-4). In this study, bifurcation angles are measured from the M1 segment of the middle cerebral artery and related to the presence of an aneurysm.

Methods: Patient data for 119 individual middle cerebral artery (MCA) aneurysm cases was acquired for retrospective review of CT-angiograms and analysis via 3D reconstruction from a GE Advantage Workstation. Data for 27 patients met inclusion criteria for the study. The 3D scans were evaluated for MCA M1 segment bifurcation angle on the affected side; assessment of the contralateral bifurcation angle served as the control.

Results: Results were calculated using Microsoft Excel and Matlab. Based on the data there is an average bifurcation angle of 110.13 degrees with a standard deviation of 31.24 degrees in MCA M1 segments that do not have an aneurysm present. There is an average bifurcation angle of 166.61 degrees with a standard deviation of 37.33 degrees at bifurcation points that possess an aneurysm. A Mann-Whitney test was performed on the data in Matlab and a p-value of 1.1662X10^-06 was obtained.

Conclusions: The data suggest that there is a relationship between the bifurcation angle of the MCA and presence of MCA aneurysm. Our results indicate that there is a statistically significant difference between our control and affected populations. Further studies are needed to determine if this biomorphometric parameter is of clinical use in prognosticating aneurysm development and rupture status.

Patient Care: An elucidation of the factors that are involved in the formation of aneurysms will allow physicians additional tools for assessing a patient's risk for the development and subsequent rupture of an intracranial aneurysm. Furthermore, with better prognostication there will ideally be a decrease in traumatic cerebrovascular events such as subarachnoid hemorrhage.

Learning Objectives: By the conclusion of the session, participants should be able to: 1) Investigate the relationship between aneurysm presence and bifurcation angles of the M1 segment of middle cerebral artery. 2) Standardize methods for measuring bifurcation angles of neurovasculature. 3) Better understand the effect of bifurcation angles on cerebral blood flow.

References: 1. Murray, Cecil D. The Physiological Principle of Minimum Work Applied to the Angle of Branching of Arteries. The Journal of General Physiology. 1926; 835-841. 2. Ingebrigtsen, Tor et al. Bifurcation geometry and the presence of cerebral artery aneurysms. Journal of Neurosurgery. 2004; 101:108-113 3. Kasuya, Hidetoshi et al. Angles between A1 and A2 Segments of the Anterior Cerebral Artery Visualized by Three-dimensional Computed Tomographic Angiography and Association of Anterior Communicating Artery Aneurysms. Surgical Anatomy. 1999; 45(1) 4. Munoz, Carolina V. Characterization of Intracranial Aneurysms in Middle Cerebral Artery (MCA) (Master’s Thesis). Retrieved from http://diposit.ub.edu/dspace/handle/2445/15562