Patient-specific Analyses Reveal Differences In Hemodynamic And Morphological Parameters Between Growing And Stable Unruptured Intracranial Aneurysms

Introduction: Although image-derived parameters such as wall shear stress (WSS), flow rate (FR), aspect ratio (AR), size ratio (SR), and non-sphericity index (NSI) were previously linked to risks of intracranial aneurysm (IA) growth, findings across studies have been inconsistent. Here, we revisit existing hemodynamic and morphological metrics and compare them between stable and growing IAs. We hypothesize that some may differentiate growing and stable trajectories of IAs. Methods: Unruptured IA cases between 2018-2020 were identified from UCLA Medical Center electronic medical records, with follow-up data used to determine growth status. From CTA/MRA images, models of 16 stable and 20 growing unruptured IA cases were reconstructed. Aneurysm diameter, height, neck width, surface area, volume, parent artery diameter, AR, SR, NSI, volume ratio, and surface area ratio were calculated. With data from hemodynamic simulations, we also measured FR and WSS. To capture spatial variations in hemodynamics, we calculated location-dependent mean deviation of WSS and FR at 3 locations within an aneurysm: neck, body, and dome. Pearson chi-square tests were used to compare background variables between groups. MANOVA was employed to compare the index values between stable and growing IAs. Results: Variables including location, diameter, race, history of smoking, and SAH were not significantly different between groups (p>>.05). Gender (p=0.06) and multiplicity (p=0.06) approached significance. Among the size-related and morphological parameters described above, only IA height (3.07±1.94mm vs. 5.49±3.61mm, p=0.03), neck width (4.93±1.42mm vs. 7.14±3.78mm, p=0.04), and size ratio (1.40±0.62 vs. 2.27±1.27, p =0.02) were significantly different (stable vs. growing, respectively). Growing IA had significantly higher FR spatial variation (0.43±0.35 vs. 0.75±0.44; p=0.03) and WSS spatial variations (0.24±0.20 vs. 0.49±0.28; p=0.008). Conclusions: Our findings support that location-dependent hemodynamic variations and SR may be potential risk factors of IA growth. Upon validation in larger studies, these parameters may aid in early identification of incidentally found IAs’ trajectories.