[CT-based morphological and hemodynamics analysis for rupture risk of mirror intracranial aneurysm]

Objective: To compare the morphological and hemodynamic features of mirror intracranial aneurysms (MIAs) on CT angiography (CTA), and to elucidate the rupture risk factors of MIAs. Methods: This study retrospectively collected 29 patients with 58 digital subtraction angiography (DSA) or surgically confirmed MIAs from January 2010 to December 2016 in Jinling Hospital, Medical School of Nanjing University. Among them, there are 6 males and 23 females, aged from 40 to 83 (61±11) years old. Based on the results of hemorrhagic manifestation, 58 MIAs were divided as the ruptured (n=29) group and unruptured group (n=29). In addition, according to the location of aneurysms, they were further divided into the subgroup of posterior communicating MIAs (n=32) and non-posterior communicating MIAs (n=26). Clinical data of the patients and the morphological parameters of the MIAs were collected. Computational fluid dynamics (CFD) analysis was performed to obtain hemodynamic parameters, such as pressure (P), wall shear stress (WSS), wall shear stress gradient (WSSG), and oscillatory shear index (OSI). The coefficient of variation (CV) was used to describe the aforementioned hemodynamic parameters of intracranial aneurysms, so the index after CV adjustment is expressed as P_CV , WSS_CV , WSSG_CV , OSI_CV . Characteristics between ruptured and unruptured groups were compared. Conditional logistic regression analysis was conducted to evaluate the rupture risk factors of MIAs. Results: Among the 29 pairs of mirror aneurysms, 16 pairs were distributed in bilateral posterior communicating arteries (55%), 9 pairs distributed in bilateral middle cerebral arteries (31%), and 4 pairs distributed in bilateral internal carotid arteries (14%). Compared with the unruptured MIAs group, the ruptured aneurysms group usually had a larger maximum diameter, neck width, and size ratio (SR) [4.98 (3.18, 6.79) mm vs 3.20 (2.10, 4.31) mm, 4.19 (3.46, 5.95) mm vs 4.05 (3.23, 5.02) mm, 1.69 (0.81, 2.28) vs 0.96 (0.67, 1.49)] (all P<0.05). In the subgroup hemodynamic analysis of MIAs, the ruptured aneurysms had higher WSS_CV and WSSG_CV than the contralateral unruptured ones [1.00(0.87, 1.21) vs 0.65(0.57, 0.87), 1.09(0.56, 1.90) vs 0.57(0.50, 1.13), 1.52 (1.34, 1.80) vs 1.21 (1.07, 1.38), 1.52±0.46 vs 1.21±0.23] (all P<0.05), while the P_CV was lower than the contralateral unruptured ones [0.004 (0.002, 0.008) vs 0.010 (0.006, 0.013), 0.003 (0.002, 0.011) vs 0.009 (0.002, 0.066)] (both P<0.05). Logistic regression analysis showed that high WSSG_CV was an independent risk factor for MIAs rupture (OR=279.20(95%CI:1.10-71 028.28)). Conclusion: The maximum diameter, neck width, and SR were considered as a reliable morphological parameters to distinguish the ruptured status of MIAs, higher WSSG_CV in the aneurysm sac are highly correlated with MIAs rupture.