Insights into the pathogenesis of cerebral fusiform aneurysms: high-resolution MRI and computational analysis

Abstract

BackgroundIntracranial fusiform aneurysms are complex and poorly characterized vascular lesions. High-resolution magnetic resonance imaging (HR-MRI) and computational morphological analysis may be used to characterize cerebral fusiform aneurysms.ObjectiveTo use advanced imaging and computational analysis to understand the unique pathophysiology, and determine possible underlying mechanisms of instability of cerebral fusiform aneurysms.MethodsPatients with unruptured intracranial aneurysms prospectively underwent imaging with 3T HR-MRI at diagnosis. Aneurysmal wall enhancement was objectively quantified using signal intensity after normalization of the contrast ratio (CR) with the pituitary stalk. Enhancement between saccular and fusiform aneurysms was compared, as well as enhancement characteristics of fusiform aneurysms. The presence of microhemorrhages in fusiform aneurysms was determined with quantitative susceptibility mapping (QSM). Three distinct types of fusiform aneurysms were analyzed with computational fluid dynamics (CFD) and finite element analysis (FEA).ResultsA total of 130 patients with 160 aneurysms underwent HR-MRI. 136 aneurysms were saccular and 24 were fusiform. Fusiform aneurysms had a significantly higher CR and diameter than saccular aneurysms. Enhancing fusiform aneurysms exhibited more enhancement of reference vessels than non-enhancing fusiform aneurysms. Ten fusiform aneurysms underwent QSM analysis, and five aneurysms showed microhemorrhages. Microhemorrhage-positive aneurysms had a larger volume, diameter, and greater enhancement than aneurysms without microhemorrhage. Three types of fusiform aneurysms exhibited different CFD and FEA patterns.ConclusionFusiform aneurysms exhibited more contrast enhancement than saccular aneurysms. Enhancing fusiform aneurysms had larger volume and diameter, more enhancement of reference vessels, and more often exhibited microhemorrhage than non-enhancing aneurysms. CFD and FEA suggest that various pathophysiological processes determine the formation and growth of fusiform aneurysms.

Vessel wall imaging with advanced flow suppression in the characterization of intracranial aneurysms following flow diversion with Pipeline embolization device

“…Although the exact nature of such enhancement will remain a matter of some conjecture, based on its consistency we propose that it reflects both the unprecedented spatial resolution and remarkable sensitivity of MRI to small concentrations of modern high-relaxivity gadolinium chelates, the latter exceeding the sensitivity of X-ray based techniques to iodine by several orders of magnitude 18 19. Notably, five aneurysms in our series were morphologically fusiform, previously reported to enhance more strongly, which may partly explain the results 20…”

“…Accordingly, previously reported approaches to normalization and internal signal references may be beneficial additions to the subjective, qualitative approach described herein 31 32. Moreover, the enhancement might be related to other phenomena, including thickening of the arterial wall, associated vasculopathy, thrombosed aneurysms, or artifactual sources 20 33 34…”

Semiautomated 3D mapping of aneurysmal wall enhancement with 7T-MRI

“…An average of 62 spokes per mm 2 were generated. Only saccular aneurysms were included in the morphological analysis (Table 1 ) as it has been described that fusiform aneurysms undergo different biological processes 19 . The entire cohort was included in validation of the AWE semi-automated method.…”

Can Endovascular Treatment of Fusiform Intracranial Aneurysms Restore the Healthy Hemodynamic Environment?–A Virtual Pilot Study

“…However, other studies reported a higher risk of hemorrhage for FIAs larger than 10 mm ( 22 , 23 ). Furthermore, a very recent MRI study by Sabotin et al ( 24 ) demonstrated the presence of increased contrast enhancement in FIAs, which was associated with microhemorrhage and pathophysiological processes.…”