Introducing the Rupture Criticality Index to Compare Risk Factor Combinations Associated With Aneurysmal Rupture

Background: Relative risk is insufficient to guide treatment decision-making for unruptured intracranial aneurysms. Our objective was to introduce a novel risk assessment methodology called the Rupture Criticality Index (RCI), which allows for concurrent evaluation of groups of risk factors (RFs). Methods: From a retrospective database of saccular aneurysms, we identify 915 patients and delineate 50 potential RFs for aneurysms in 11 unique locations. RF combinations for multivariable analysis were defined by aneurysm size, location, and a third variable from the study design. Data analysis was performed by applying frequency distribution methods to define the RCI of each RF combination. Results: RF combinations at greatest risk were small (4.8–8.2 mm) or medium (8.3–14.5 mm) anterior communicating aneurysms (ACoA) in male individuals (RCI 9.87–10), small ACoA in those ≤37 years or 38–55 years (RCI 8.67–8.99), medium basilar tip aneurysms (BTAs) in male individuals (RCI 10), and large (14.6–22.5 mm) BTA in Caucasians or those aged 38–55 years (RCI 9.25, 9.35, respectively). Conclusions: We introduce the concept of RCI and compare how RF combinations are associated with aneurysmal rupture. This novel approach to aneurysmal rupture identifies high-risk clinical presentations and can be used to guide clinical decision-making in patients with non-traditional risks.