Baseline Gadolinium Enhancement of the Intracranial Aneurysm Wall and Three-Dimensional Morphological Change During Long-Term Follow-Up

BACKGROUND AND PURPOSE: Previous studies showed 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 semi-automatically quantified 3D morphological 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 morphological parameters on paired baseline and follow-up scans and determined changes over time. We compared the proportion of aneurysms showing morphological change (modified Z-score <-3.5 or >+3.5) between aneurysms with and without AWE. The risk difference with 95% CI was calculated for each morphological 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 inclusion criteria. Twenty aneurysms (28%) in 18 patients showed AWE at baseline. Median follow-up was 5.8 years (IQR 4.6–6.6). For the parameter curvedness, the proportion of aneurysms showing an increase was higher in aneurysms with AWE (6 of 20, 30%) than aneurysms without AWE (2 of 52, 4%), with a risk difference of 26% (95%CI 9–49%). For the other five morphological parameters, the proportion of aneurysms with morphological change was comparable between aneurysms with and without AWE. In logistic regression analysis, AWE was associated with 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 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.

ABBREVIATIONS: AWE = aneurysm wall enhancement; AWI = aneurysm wall imaging; IBSI = imaging biomarker standardization initiative; UIA = unruptured intracranial aneurysm.