Background Ruptured basilar artery perforator aneurysms (BAPAs), defined as microaneurysms which develop in basilar perforator arteries without direct involvement of the basilar trunk, represent a rare cause of subarachnoid hemorrhage (SAH). The diagnosis of BAPAs is difficult because of their small size, with high rates of negative angiography. The development of high-resolution MRI could increase the diagnostic performance. In this study we describe the usefulness of susceptibility weighted imaging (SWI) for the diagnosis of ruptured BAPAs.
Methods In a case series, we retrospectively collected data of patients admitted to our institution from 2018 to 2021 for SAH with negative CT angiography who underwent MRI (including SWI) and DSA during hospitalization.
Results Eight patients with a definitive diagnosis of ruptured BAPA and five patients with a definitive diagnosis of angiogram-negative SAH were included. In all of the patients with BAPAs MRI showed a focal, thick, semi-circumferential SWI hypointensity covering the vessel wall at the level of the BAPA subsequently revealed on DSA; this phenomen is known as ‘SWI capping’. No SWI capping was observed in the five patients with a definitive diagnosis of angiogram-negative SAH.
Conclusion SWI capping appears to be a reliable indirect sign for the diagnosis and localization of ruptured BAPAs, a rare form of microaneurysm easily misdiagnosed on DSA in initial angiogram-negative SAH.
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Twitter @FrancoisZhu, @patricioemusz
Contributors FZ, LL, SB, ALD, PM, IM, SP, ES, MB, BG, RA acquired, analyzed and interpreted the data for the work, drafted and revised it for intellectual content and approved the final version to be published.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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