Qualitative and Quantitative Wall Enhancement on Magnetic Resonance Imaging Is Associated With Symptoms of Unruptured Intracranial Aneurysms

Abstract

Background and purpose: Aneurysmal wall enhancement (AWE) on vessel wall magnetic resonance imaging (VW-MRI) has been described as a new imaging biomarker of unstable unruptured intracranial aneurysms (UIAs). Previous studies of symptomatic UIAs are limited due to small sample sizes and lack of AWE quantification. Our study aims to investigate whether qualitative and quantitative assessment of AWE can differentiate symptomatic and asymptomatic UIAs.

Methods: Consecutive patients with UIAs were prospectively recruited for vessel wall magnetic resonance imaging at 3T from October 2014 to October 2019. UIAs were categorized as symptomatic if presenting with sentinel headache or oculomotor nerve palsy directly related to the aneurysm. Evaluation of wall enhancement included enhancement pattern (0=none, 1=focal, and 2=circumferential) and quantitative wall enhancement index (WEI). Univariate and multivariate analyses were used to identify the parameters associated with symptoms.

Results: Two hundred sixty-seven patients with 341 UIAs (93 symptomatic and 248 asymptomatic) were included in this study. Symptomatic UIAs more frequently showed circumferential AWE than asymptomatic UIAs (66.7% versus 17.3%, P<0.001), as well as higher WEI (median [interquartile range], 1.3 [1.0-1.9] versus 0.3 [0.1-0.9], P<0.001). In multivariate analysis, both AWE pattern and WEI were independent factors associated with symptoms (odds ratio=2.03 across AWE patterns [95% CI, 1.21-3.39], P=0.01; odds ratio=3.32 for WEI [95% CI, 1.51-7.26], P=0.003). The combination of AWE pattern and WEI had an area under the curve of 0.91 to identify symptomatic UIAs, with a sensitivity of 95.7% and a specificity of 73.4%.

Conclusions: In a large cohort of UIAs with vessel wall magnetic resonance imaging, both AWE pattern and WEI were independently associated with aneurysm-related symptoms. The qualitative and quantitative features of AWE can potentially be used to identify unstable intracranial aneurysms.

Keywords: biomarkers; headache; inflammation; intracranial aneurysm; magnetic resonance imaging.

Figure 1.

Example case for image processing. First row, the original images. Second row, the contours of the aneurysm wall and the ROI (region of interests) of the white matter for normalization in calculation. The left column shows the pre-contrast vessel wall images on which the contour of ROI was traced manually, and the right column shows the post-contrast vessel wall images on which the contour of ROI was matched automatically, and the contour of ROI was segmented into quarters automatically.

Figure 2.

Flowchart of patient selection.

Figure 3.

Comparison of the aneurysm wall enhancement between asymptomatic and symptomatic aneurysms. A, bar graphs comparing the aneurysm wall enhancement pattern for asymptomatic and symptomatic aneurysms. Pattern 0, no wall enhancement; pattern 1, focal wall enhancement; pattern 2, circumferential wall enhancement. B, plots comparing wall enhancement index (WEI) for asymptomatic and symptomatic aneurysms. Box-and-whisker plots represent medians (lines within boxes), interquartile ranges (upper and lower ends of boxes), greatest and least values (top and bottom lines), and outliers (data points beyond top and bottom lines) for WEI.

Figure 4.

Representative cases of patients with symptomatic and asymptomatic intracranial aneurysms. A, Images of a 52-year-old man with an asymptomatic aneurysm at the right internal carotid artery terminal, measuring 3.8mm. B, Images of a 64-year-old woman with oculomotor nerve palsy and an aneurysm at the right internal carotid artery terminal, measuring 9.3mm. C, Images of a 51-year-old man with sentinel headache and an aneurysm at the top of basilar artery, measuring 16mm. Aneurysm wall hyper intensity is present prior to contrast administration, which is uncommon in the current cohort (9 aneurysms in the whole dataset). Potential explanation might be micro bleeding, which may be related to sentinel headache. For each aneurysm represented on a row, a digital subtraction angiography image is shown in the left column, a vessel wall image is in the middle column, and a post-contrast vessel wall image is shown in the right column.