Multiple flow-related intracranial aneurysms in the setting of contralateral carotid occlusion: Coincidence or association?

The prevalence of intracranial aneurysms (IAs) is higher in patients with internal carotid artery (ICA) stenosis, likely due to alterations in intracranial hemodynamics. Severe stenosis or occlusion of one ICA may result in increased demand and altered hemodynamics in the contralateral ICA, thus increasing the risk of contralateral IA formation. In this article, we discuss a relevant case and a comprehensive literature review as it pertains to the association of ICA stenosis and IA. Our patient was a 50-year-old female with a chronic asymptomatic right ICA occlusion who presented with diffuse subarachnoid hemorrhage. Emergent angiography revealed left-sided A1-A2 junction, paraclinoid, left middle cerebral artery (MCA) bifurcation, and left anterior temporal artery aneurysms. Brisk filling of the right anterior circulation through the anterior communicating artery was also identified, signifying increased demand on the left ICA circulation. Complete obliteration of all aneurysms was achieved with coil embolization and clipping. For our literature review, we searched the PubMed and EMBASE databases for case reports and case series, as well as references in previously published review articles that described patients with concurrent aneurysms and ICA stenosis. We selected articles that provided adequate information about the case presentations to compare aneurysm and patient characteristics. Our review revealed a higher number of patients with multiple aneurysms contralateral (25%) to rather than ipsilateral to (6%), the ICA stenosis. We discuss the pathogenesis and management of multiple flow-related IA in the context of the existing literature related to concurrent ICA stenosis and IA.