Original ArticleFocal Aneurysm Wall Enhancement on Magnetic Resonance Imaging Indicates Intraluminal Thrombus and the Rupture Point
Introduction
Vessel wall imaging (VWI) is an emerging diagnostic magnetic resonance imaging (MRI) technique to visualize aneurysm wall structures. Since Matouk et al.1 suggested that aneurysm wall enhancement (AWE) could be used to identify the site of rupture in patients with multiple intracranial aneurysms, several studies on aneurysm wall imaging including ruptured intracranial aneurysms have been published.2, 3, 4, 5, 6, 7, 8, 9, 10 Current consensus has suggested that contrast-enhanced VWI is clinically useful for detecting ruptured intracranial aneurysms with high sensitivity and specificity.11, 12 However, there has been considerable argument as to whether the site of contrast enhancement corresponds to the aneurysm wall, intraluminal thrombus, or surrounding brain tissues. Actually, the images in published articles have revealed various patterns of AWE, including circumferential and/or focal wall enhancement.1, 2, 3, 4, 5, 6, 7, 8, 9 Potentially, wall structure at the rupture point has been considered extremely thin and would be beyond the spatial resolution even in high-field MRI.13, 14, 15, 16 Hu et al.17 demonstrated histopathologic correlation in a case of ruptured aneurysm between inflammation in the wall and AWE findings, however, the association between hemostatic clots at the rupture point was not clearly demonstrated. In the present retrospective study, we explored the clinical significance of VWI in patients with subarachnoid hemorrhage (SAH) by investigating intraoperative inspection with available histopathologic specimens of aneurysms.
Section snippets
Methods
The authorized local ethical committee approved this retrospective study and patient informed consent was waved. A total of 63 patients who had SAH associated with rupture of a saccular intracranial aneurysm were treated in our hospital from April 2017 through December 2018. Patients were initially evaluated by computed tomography (CT) and followed by CT angiography. After the diagnosis of SAH, general anesthesia was performed for all patients. Patients with high-grade SAH who were critical
Results
In all patients, MRI was performed safely and the aneurysm was treated without any adverse events. Demographic data for all patients, the major anatomic features of the aneurysms, and the patterns of AWE are summarized in Table 1. The patients included 4 men and 20 women (mean age: 70 years, range: 37–91 years). The location of the ruptured aneurysm was as follows: 10 in the internal carotid artery, 7 in the middle cerebral artery, 4 in the anterior cerebral artery, and 3 in the vertebrobasilar
Discussion
This retrospective study investigated AWE in ruptured intracranial aneurysms and focused on the correlations with histopathologic aneurysm wall architecture. Regarding the pathophysiology of AWE in ruptured intracranial aneurysms, it is hypothesized to reflect endothelial damage associated with mural disruption or an inflammatory healing process.1, 19 By intraoperative inspection and histopathologic investigation, the present study revealed that there were 2 patterns of aneurysm wall
Conclusions
Two AWE patterns were seen in ruptured intracranial aneurysms. Focal AWE revealed by VWI of ruptured intracranial aneurysms might indicate fresh intraluminal thrombus and shows the site of rupture. This finding can provide useful information regarding lesion anatomy before treating the patient by microsurgical clipping or endovascular coiling. On the contrary, the mechanism of circumferential AWE remains unclear and further histopathologic studies are warranted.
Acknowledgement
The authors thank the magnetic resonance imaging (MRI) Team at Hiroshima City Asa Citizens Hospital for special efforts when performing vessel wall imaging.
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2021, Seminars in Ultrasound, CT and MRICitation Excerpt :Aneurysm wall enhancement (AWE) may reflect rupture-induced inflammation or inflammatory changes related to aneurysm formation or growth. Studies have shown, however, that AWE is nonspecific and has been associated with macrophage infiltration, neovascularization, atherosclerotic changes, and wall-adherent thrombus.74-78 The unique geometric morphology of aneurysms requires several technical VWI considerations.
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2021, Neuroimaging Clinics of North AmericaCitation Excerpt :Although several studies have explored histopathologic correlation, sample sizes have been small, limiting the generalizability of these findings. In a small prospective imaging study, Matsushige and colleagues78 reported that aneurysms with focal enhancement had thin walls, whereas those with circumferential aneurysm wall enhancement had thick walls. Larsen and colleagues79 examined 5 unruptured middle cerebral artery (MCA) aneurysms, which demonstrated strong enhancement on IVWI.
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Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.