Increased Wall Enhancement Extent Representing Higher Rupture Risk of Unruptured Intracranial Aneurysms

Abstract

Objective: This study aims to investigate the relationship between aneurysm wall enhancement and clinical rupture risks based on the magnetic resonance vessel wall imaging (MR-VWI) quantitative methods.

Methods: One hundred and eight patients with 127 unruptured aneurysms were prospectively enrolled from Feburary 2016 to October 2017. Aneurysms were divided into high risk (≥10) and intermediate-low risk group (<10) according to the PHASES (Population, Hypertension, Age, Size of aneurysm, Earlier SAH history from another aneurysm, Site of aneurysm) scores. Clinical risk factors, aneurysm morphology, and wall enhancement index (WEI) calculated using 3D MR-VWI were analyzed and compared.

Results: In comparison of high-risk and intermediated-low risk groups, univariate analysis showed that neck width (4.5±3.3 mm vs. 3.4±1.7 mm, p=0.002), the presence of wall enhancement (100.0% vs. 62.9%, p<0.001), and WEI (1.6±0.6 vs. 0.8±0.8, p<0.001) were significantly associated with high rupture risk. Multivariate regression analysis revealed that WEI was the most important factor in predicting high rupture risk (odds ratio, 2.6; 95% confidence interval, 1.4-4.9; p=0.002). The receiver operating characteristic (ROC) curve analysis can efficiently differentiate higher risk aneurysms (area under the curve, 0.780; p<0.001) which have a reliable WEI cutoff value (1.04; sensitivity, 0.833; specificity, 0.67) predictive of high rupture risk.

Conclusion: Aneurysms with higher rupture risk based on PHASES score demonstrate increased neck width, wall enhancement, and the enhancement intensity. Higher WEI in unruptured aneurysms has a predictive value for increased rupture risk.

Keywords: Intracranial aneurysm, Unruptured; Natural history; Rupture risk; Vessel wall MRI.

Fig. 1.

Three different MR imaging sequences : with ×400% zoomed images. A : TOF MRA. B : Sag CUBE T1 pre-gadolinium. C : Sag CUBE T1 post-gadolinium. MRA : magnetic resonance angiography, TOF : time-of-flight.

Fig. 2.

Representing case. Measurement of signal value (red box). A : Pre-contrast imaging. B : Post-contrast imaging. C : Selected a region of maximum signal using ring tool.

Fig. 3.

Representative pre- and post-contrast imaging of aneurysm with different wall enhancement types. A-C : No enhancement (arrowheads). D-F : Partial enhancement (short arrow). G-I : circumferential enhancement (long arrow).

Fig. 4.

High rupture risk (PHASES score ≥10) was efficiently differentiated on ROC curve (AUC, 0.780; p<0.001). Higher WEI than cutoff value (1.04; sensitivity, 0.833; specificity, 0.67) predict high rupture risk. PHASES : Population, Hypertension, Age, Size of aneurysm, Earlier SAH history from another aneurysm, Site of aneurysm, ROC : receiver operating characteristics curve, AUC : area under the curve, WEI : wall enhancement index.