Article
Focal enhancement in intracranial aneurysms in MR vessel wall imaging is colocalised with low-flow conditions and associated with histologic signs of inflammation
Fokales Kontrastmittelenhancement intrakranieller Aneurysmen im MR vessel wall imaging ist kolokalisiert mit vermindertem Flussund histologischen Zeichen der Inflammation
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Published: | June 26, 2020 |
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Objective: Circumferential enhancement has been proposed as a possible imaging marker of a higher risk of rupture in intracranial aneurysms. Hemodynamic studies have identified low flow conditions as possibly associated with focal enhancement and rupture sites. Focal enhancement is frequently encountered in unruptured aneurysms on MR vessel wall imaging, but its implication for risk stratification and patient management remains unclear. This study was conducted to investigate the association of focal wall enhancement in unruptured intracranial aneurysms with focal hemodynamic conditions and histologic markers of wall inflammation and degeneration.
Methods: Patients with an unruptured middle cerebral artery aneurysm who underwent 3T MR vessel wall imaging showing focal wall enhancement and DSA were retrospectively identified. Aneurysms were dichotomized either into group 1 (enhancement of <50% of the aneurysm surface) or group 2 (≥50% enhancement). Enhanced vessel wall regions were manually segmented and co-registered with an aneurysm surface mesh. Hemodynamic simulations derived from 3D rotational angiography data were carried out. Average wall shear stress (AWSS), low shear area (LSA), and maximum oscillatory shear index (maxOSI) were compared between enhanced regions and the entire aneurysm surface, and between group 1 and group 2. Histologic features were compared between group 1 and 2.
Results: Twenty-two aneurysms were analyzed. Lower AWSS, increased LSA and lower maxOSI were significantly associated with enhanced regions. AWSS was significantly lower in aneurysms showing focal enhancement of ≥50% of the aneurysm surface. Aneurysms with a greater extent of focal enhancement exhibited histologic signs of inflammatory and degenerative changes of the aneurysm wall, whereas these changes could not be detected in aneurysms with enhancement in <50% of the aneurysm surface.
Conclusion: Focal wall enhancement is associated with low flow conditions and inflammatory changes. Not only circumferential, but also focal wall enhancement in a larger extent could serve as a surrogate marker for aneurysm instability.