Morphological Characteristics of Ruptured Brain Aneurysms: A Systematic Literature Review and Meta‐Analysis

Background It is unclear what morphological features of brain aneurysms are better at predicting risk of rupture. We conducted a meta‐analysis to analyze the best morphological determinants of rupture status. Methods The Nested Knowledge platform was used to perform a search of articles reporting on aneurysm size, aspect ratio (AR), size ratio (SR), ellipticity index, nonsphericity index, and undulation index. The mean differences between ruptured and unruptured aneurysms were used to calculate effect sizes. Results A total of 63 studies with 13 025 aneurysms were included: 6966 ruptured aneurysms and 6059 unruptured aneurysms. Ruptured aneurysms had a larger size ( P <0.001), AR ( P <0.001), SR ( P <0.001), ellipticity index ( P =0.049), and nonsphericity index ( P =0.049) compared with unruptured aneurysms. The mean size of ruptured aneurysms was 6.1 mm (95% CI, 5.6–6.5). The size of ruptured and unruptured aneurysms was similar in the anterior cerebral artery ( P =0.28), anterior communicating artery ( P =0.31), and basilar artery ( P =0.51). The mean AR of ruptured aneurysms was 1.5 (95% CI, 1.4–1.6), and the mean SR was 2.3 (95% CI, 2.1–2.5). For mirror aneurysms, the mean AR was 1.2 (95% CI, 1.2–1.5), and the mean SR was 2.2 (95% CI, 2.1–2.5). Conclusions Size is not significantly different between ruptured and unruptured aneurysms located in the anterior cerebral artery, anterior communicating artery, and basilar artery. SR is significantly different between ruptured and unruptured aneurysms in all locations. A mean AR of 1.5 and SR of 2.3 are the thresholds associated with ruptured aneurysm status.