Vessel wall enhancement in brain arteriovenous malformations: associations with imaging and histopathological markers of instability.

In brain arteriovenous malformations (bAVMs), whether vessel wall enhancement on magnetic resonance vessel wall imaging (VWI) is associated with hemorrhage and other imaging and histopathological markers of instability remains unclear. We retrospectively analyzed 26 consecutive patients with bAVMs who underwent VWI. Post-contrast T1-weighted 3D turbo spin-echo images were evaluated by two independent readers for the presence and pattern of vessel wall enhancement (focal, circumferential, or diffuse). Perifocal edema, hemosiderin deposition, and luminal thrombosis were assessed on FLAIR, T2*-weighted, and precontrast T1-weighted images, respectively. Associations between VWI enhancement and clinical and imaging findings were examined using univariate analyses. In four surgical cases, VWI-enhancing intranidal varices were correlated with histopathological findings and compared with one non-enhancing varix. VWI enhancement was observed in 19 of 26 patients. All 10 patients with hemorrhagic presentation were VWI-positive (P = 0.023), and in 8 of these 10 cases, the enhancing portion was adjacent to the hematoma. In the overall cohort, VWI enhancement was associated with perifocal edema (P = 0.005) and hemosiderin deposition (P = 0.028), but not with luminal thrombosis. In the non-hemorrhagic subgroup (n = 16), enhancement remained associated with perifocal edema (P = 0.041). Histopathological examination of VWI-enhancing varices demonstrated vessel wall inflammation, thinning, organized thrombus, and hemosiderin deposition, whereas the non-enhancing varix showed only minimal intimal inflammation. VWI enhancement may serve as a marker of local pathological activity in bAVMs. However, because enhancement in ruptured cases may partly reflect post-hemorrhagic change, its predictive value for future hemorrhage requires prospective validation.