Introduction: The prevalence of intracranial aneurysms is estimated to be around 3% in the general population. Although these are often incidental findings, they potentially carry the risk of rupture, with all of the devastating consequences of SAH.
State of the art: Several risk factors of aneurysm rupture have been identified, including aneurysm size, irregular shape, and location. Although it is widely accepted that the risk of rupture increases with size, small aneurysms remain the cause of a significant percentage of aneurysmal SAH. Up to 30% of patients with acute aneurysmal SAH have multiple aneurysms. Determining the site of rupture in these patients can be challenging, given that the results of imaging studies and clinical symptoms are sometimes inconclusive. It would be extremely useful to identify new imaging biomarkers of aneurysm instability which could have an impact on patient management and qualification for treatment. High-resolution vessel wall magnetic resonance imaging (HR-VW MRI) opens up new possibilities for improved characterisation of intracranial vasculature. One of the most promising clinical applications of this new imaging tool is the evaluation of intracranial aneurysms.
Clinical implications: Aneurysm wall enhancement (AWE) on HR-VW MRI is believed to be a marker for wall inflammation and, potentially, for aneurysm instability. In this article, we summarise the published literature on AWE with special emphasis on its use in determining the site of rupture in the setting of acute SAH in patients with multiple aneurysms, as well as its role in identifying unruptured aneurysms which are at the greatest risk of rupture.
Future directions: More and larger studies are needed to definitively establish the role of AWE on HR-VW MRI in the diagnostic workup of patients with intracranial aneurysms.
Keywords: aneurysm wall enhancement; high-resolution vessel wall magnetic resonance imaging; intracranial aneurysm; magnetic resonance imaging.