2026 Poster Presentations
P495: SIZE RATIO AS A SURROGATE FOR RISK OF ANEURYSMAL RUPTURE
Hunter Brooks1; Michael Ortiz, MD2; Joseph Camarano, MD3; Bharat Guthikonda, MD3; Farhan Siddiq, MD1; 1University of Missouri - Columbia School of Medicine; 2Presbyterian Medical Group; 3Louisiana State University - Shreveport
Introduction: Ruptured intracranial aneurysms cause substantial disability and mortality. For incidentally discovered unruptured aneurysms, management hinges on whether rupture risk outweighs treatment risk. Although absolute aneurysm size is commonly used, its predictive value has been questioned. Size ratio (SR)—an aneurysm dimension referenced to parent artery caliber—may better reflect local hemodynamics and wall stress. We evaluated whether SR discriminates rupture status more effectively than size or height alone and compared two SR definitions.
Methods: We performed a retrospective study of patients at Louisiana State University Health Shreveport who underwent 3D digital-subtraction angiography (3D-DSA) between 2019 and 2024 and were found to have ruptured or unruptured intracranial aneurysms. Direct caliper measurements were obtained on centerline-orthogonal multiplanar reconstructions.
- Size ratio 1 (SR1): maximal aneurysm height ÷ parent artery diameter.
- Size ratio 2 (SR2): maximal aneurysm diameter ÷ average parent artery diameter.
- Aspect ratio (AR): maximal height ÷ neck width.
- Parent artery diameter measurement: for side-wall aneurysms, diameter was sampled at a standardized point proximal to the neck in an orthogonal plane; for bifurcation aneurysms, the mean of the two efferent vessel diameters (sampled just distal to the apex) was used.
Continuous variables were reported as median with interquartile range (IQR) and compared with two-sample t-tests or Mann–Whitney U tests according to Shapiro–Wilk normality; categorical variables were summarized as odds ratios (OR).
Results: Eighty-four patients were included (53 unruptured, 31 ruptured). Sex, hypertension, family history of aneurysm, and bifurcation status were not associated with rupture (female OR 0.61, p=0.39; hypertension OR 1.00, p=0.99; family history OR 1.76, p=0.63; bifurcation OR 1.22, p=0.66). Absolute dimensions were not discriminative of ruptured vs unruptured aneurysms: maximal diameter (3.82mm [2.70, 5.02] vs 3.31mm [2.31, 4.80], p=0.52) and maximal height (4.30mm [3.15, 6.97] vs 3.39mm [2.41, 5.80], p=0.15). By contrast, SR1 was higher in ruptured vs unruptured aneurysms (2.22 [1.29, 3.00] vs 1.30 [0.86, 1.92], p<0.01). SR2 trended higher (1.70 [1.05, 2.75] vs 1.07 [0.85, 1.92], p=0.052), as did AR (1.63 [1.11, 2.06] vs 1.22 [1.01, 1.71], p=0.054) but were both ultimate not significant.
Conclusion: In this single-center cohort, size ratio outperformed maximum diameter and height as independent risk factors for rupture, with SR1 demonstrating a statistically significant difference between ruptured and unruptured aneurysms. SR2 and AR showed near-significant trends. These findings support further validation of SR—particularly SR1—as a standardized metric for rupture risk assessment and underscore the importance of specifying how the parent artery diameter is measured in SR-based studies.