Focal Aneurysm Wall Enhancement on Magnetic Resonance Imaging Indicates Intraluminal Thrombus and the Rupture Point

doi:10.1016/j.wneu.2019.03.209

World Neurosurgery

Volume 127, July 2019, Pages e578-e584

https://doi.org/10.1016/j.wneu.2019.03.209 Get rights and content

Background

The precise mechanism of aneurysm wall enhancement (AWE) in ruptured intracranial aneurysms on magnetic resonance vessel wall imaging (VWI) remains unclear. We explored patterns of VWI findings and correlations with intraoperative or histopathologic aneurysm wall architecture.

Methods

Twenty-four patients were evaluated by VWI before microsurgical clipping or endovascular coiling. The patterns of AWE were categorized, and the contrast ratio of AWE area was measured relative to the pituitary stalk. A total of 13 aneurysms were microsurgically inspected of the aneurysm wall and 4 were available for histopathologic evaluation.

Results

AWE was identified in 20 of 24 ruptured aneurysms. Among these 20 aneurysms, AWE was focal in 15 and circumferential in 5. Focal AWE showed significantly higher contrast ratio than circumferential AWE (P = 0.002). Histopathologic studies suggested that focal AWE indicating contrast ratio over 0.1 could be associated with fresh intraluminal thrombus at the rupture site. On the contrary, circumferential AWE suggested potential wall thickening with abundant neovascularization and inflammatory cells.

Conclusions

Two AWE patterns were seen in ruptured intracranial aneurysms. Focal AWE on magnetic resonance imaging might indicate the presence of intraluminal thrombus, and detection of this sign could be useful for identification of the rupture point before treatment.

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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Acute hemorrhagic stroke in MMD is independently associated with PCES on postcontrast VWI. PCES can help to detect the culprit vessels that are responsible for hemorrhage in patients with MMD.
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Citation 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.
Intracranial vessel wall MR imaging (VWI) is increasingly being used as a valuable adjunct to conventional angiographic imaging techniques. This article will provide an updated review on intracranial VWI protocols and image interpretation. We review VWI technical considerations, describe common VWI imaging features of different intracranial vasculopathies and show illustrative cases. We review the role of VWI for differentiating among steno-occlusive vasculopathies, such as intracranial atherosclerotic plaque, dissections and Moyamoya disease. We also highlight how VWI may be used for the diagnostic work-up and surveillance of patients with vasculitis of the central nervous system and cerebral aneurysms.
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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.

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Original ArticleFocal Aneurysm Wall Enhancement on Magnetic Resonance Imaging Indicates Intraluminal Thrombus and the Rupture Point

Background

Methods

Results

Conclusions

Introduction

Section snippets

Methods

Results

Discussion

Conclusions

Acknowledgement

World Neurosurg

Surg Neurol

Blood

Vessel wall magnetic resonance imaging identifies the site of rupture in patients with multiple intracranial aneurysms: proof of principle

Neurosurgery

Vessel wall MRI and intracranial aneurysms

J Neurointerv Surg

Does aneurysmal wall enhancement on vessel wall MRI help to distinguish stable from unstable intracranial aneurysms?

Stroke

Wall enhancement of the intracranial aneurysms revealed by magnetic resonance vessel wall imaging using three-dimensional turbo spin-echo sequence with motion-sensitized driven-equilibrium: a sign of ruptured aneurysm?

Clin Neuroradiol

Circumferential wall enhancement on magnetic resonance imaging is useful to identify rupture site in patients with multiple cerebral aneurysms

Neurosurgery

Quantitative assessment of circumferential enhancement along the wall of cerebral aneurysms using MR imaging

AJNR Am J Neuroradiol

Wall enhancement ratio and partial wall enhancement on MRI associated with the rupture of intracranial aneurysms

J Neurointerv Surg

Vessel wall enhancement in unruptured intracranial aneurysms: an indicator for higher risk of rupture? High-resolution MR imaging and correlated histologic findings

AJNR Am J Neuroradiol

Clinicopathological insights from vessel wall imaging of unruptured intracranial aneurysms

Stroke

Conventional and high-resolution vessel wall MRI of intracranial aneurysms: current concepts and new horizons

J Neurosurg

Original Article
Focal Aneurysm Wall Enhancement on Magnetic Resonance Imaging Indicates Intraluminal Thrombus and the Rupture Point