Background: Although anterior cerebral artery A1 dominancy can contribute to the formation of anterior communicating artery aneurysm (AcomA), physiological hemodynamic studies on the circle of Willis (COW) and hemodynamic stress have been insufficient. We evaluated whether such variables for A1 dominancy influence the occurrence of AcomA based on a novel time-of-flight (TOF) magnetic resonance angiography (MRA) technique.
Method: Our observational study was conducted in consecutive subjects who performed TOF-MRA images in out-patient clinic at tertiary university hospital over 4 years. Subjects were divided into AcomA or non-AcomA groups, and MRA images of subjects were analyzed using new semi-automatic software (VINT, mediimage, Inc). General demographics, anatomical features, hemodynamic variables around the COW, including signal intensity gradient (SIG) representing wall shear stress and vascular asymmetry coefficient (VAC), were compared between the groups. To prevent result errors by demographics and laboratory test, propensity score matching was used.
Result: In the study population, there were a total of 221 patients classified as AcomA group (n=71) and non-AcomA group (n=150). As compared to the non-AcomA group, the AcomA group showed a more difference in bilateral A1 radius (49.7 vs. 26.8%, p<0.001) and a higher proportion of unilateral A1 aplasia (30.9% vs 9.3%, p<0.001). In addition, the AcomA group had a larger A1 SIG difference between the two sides when bilateral A1 asymmetry intensified. The SIG difference ratio and VAC had a strong correlation, and both factors showed similar explanation power when analyzing the relationship according to presence or absence of AcomA
Conclusion: Our study on AcomA and A1 dominancy suggests that the occurrence of AcomA is closely related to the change of hemodynamic properties of COW. To identify other intracranial aneurysm generation mechanisms, further studies using new and feasible techniques are needed for easy interpretation of hemodynamic stress.