Decreased wall shear stress on 4D-flow-MRI is associated with wall instability of unruptured intracranial aneurysm

The wall instability of unruptured intracranial aneurysms (UIAs) is associated with aneurysm growth or rupture. The wall shear stress (WSS) of 4D-flow-MRI can indicate hemodynamic abnormalities on the aneurysm wall. Aneurysm wall enhancement (AWE) of vessel wall MRI (VWI) and volume transfer constant (K^trans) of dynamic contrast-enhanced MRI (DCE-MRI) can indicate inflammation and permeability changes of the unstable aneurysm wall. We hypothesize that the WSS of UIAs is not only associated with AWE and K^trans but also with the risk of growth or rupture derived from the ELAPSS or PHASES scores of the aneurysm.

A cross-sectional retrospective analysis was performed on patients with UIAs who underwent 3.0 T VWI, DCE-MRI, and 4D-flow-MRI in our hospital from January 2018 to October 2023. AWE, K^trans, and WSS were obtained by VWI, DCE-MRI, and 4D-flow MRI, respectively. AWE pattern (AWEP) and wall enhancement index (WEI) were used to evaluate AWE. 3- and 5-year aneurysm growth risk and 5-year rupture risk were predicted based on ELAPSS and PHASES scores, respectively. Correlations between parameters were assessed using Spearman's correlation coefficient or logistic regression.

Ninety-six aneurysms in 78 patients (53 women) were included in the study. WSS differed across AWEP subgroups (p < 0.001). WSS was negatively correlated with AWEP, WEI, and K^trans (rs = -0.35, rs = -0.44, and rs = -0.25; p < 0.001). Multiple logistic regression indicated that decreased WSS was associated with higher odds of AWE (OR: 0.65, 95 % CI: 0.48-0.87). WSS was negatively correlated with the 3- and 5-year growth risk and the 5-year risk of rupture (rs = -0.47, rs = -0.44, and rs = -0.50; p < 0.001).

WSS on 4D-flow-MRI of aneurysms is inversely associated with AWEP, WEI, and K^trans and growth and rupture risk. The decrease in WSS on 4D-flow-MRI may provide valuable information for assessing aneurysm wall instability.