Baseline Gadolinium Enhancement of the Intracranial Aneurysm Wall and 3D Morphologic Change during Long-Term Follow-Up.

Abstract

Background and purpose: Previous studies have shown that intracranial aneurysm wall enhancement (AWE) is associated with aneurysm growth or rupture. These studies assessed growth with manual 2D measurements or eyeballing, both of which are prone to interobserver variability. To minimize this variability, we assessed the association between AWE and semiautomatically quantified 3D morphologic changes in aneurysms during long-term follow-up.

Materials and methods: We included patients with an unruptured intracranial aneurysm who had baseline MR aneurysm wall imaging and were followed with MR or CT angiography for ≥1 year. We used in-house-developed software to measure six 3D morphologic parameters on paired baseline and follow-up scans and determined changes with time. We compared the proportion of aneurysms showing morphologic change (modified z score, ≤3.5 or ≥3.5) between aneurysms with and without AWE. The risk difference was calculated with 95% CI for each morphologic parameter. For parameters with a statistically significant change difference between aneurysms with and without AWE, we calculated ORs with 95% CI in a univariable logistic regression model and adjusted for aneurysm size in a bivariable model.

Results: Sixty-two patients with 72 unruptured intracranial aneurysms met the inclusion criteria. Twenty aneurysms (28%) in 18 patients showed AWE at baseline. The median follow-up was 5.8 years (interquartile range, 4.6-6.6 years). For the parameter curvedness, the proportion of aneurysms showing an increase was higher in aneurysms with AWE (6 of 20, 30%) than in aneurysms without AWE (2 of 52, 4%), with a risk difference of 26%; 95% CI, 9-49. For the other 5 morphologic parameters, the proportion of aneurysms with morphologic change was comparable between aneurysms with and without AWE. In logistic regression analysis, AWE was associated with a curvedness increase (crude OR, 10.7; 95% CI, 2.2-78.9, adjusted OR, 6.1; 95% CI, 1.01-50.3).

Conclusions: AWE was associated with aneurysm shape change during long-term follow-up, with an increase in 3D quantified curvedness that was independent of aneurysm size. This result reinforces previous findings that AWE is associated with aneurysm instability, in particular curvedness increase, and suggests that curvedness could be a suitable parameter to capture aneurysm instability. Future studies need to investigate whether an increase in this parameter predicts aneurysmal rupture.