Safety and Efficacy of Endovascular Therapy in Distal Vessel Occlusions

Endovascular therapy (EVT) is strongly indicated for acute ischemic stroke (AIS) caused by large vessel occlusion (LVO) in the anterior and posterior circulation according to international recommendations, but the benefit is unclear for AIS patients with distal vessel occlusions (DVO) since these patients were systematically excluded from the vast majority of randomized controlled clinical trials (RCTs) establishing the safety and efficacy of EVT. Observational data from multiple registries appear promising but also highlight numerous challenges: identification of DVO is not straightforward and may necessitate advanced imaging, potential clinical benefits from the intervention are more limited than in LVOs since DVO patients present with milder deficits, recanalization of smaller caliber arteries is technically challenging and associated with greater risk for complications namely symptomatic intracranial hemorrhage and vessel perforation. There are multiple ongoing RCTs evaluating the safety and efficacy of EVT in AIS patients with DVOs in Europe, North America and Australasia. In view of the former considerations the current narrative review aims to present the different approaches to define DVO, summarize the epidemiology and natural history of DVO under best medical treatment, outline the diagnostic utility of different imaging modalities and critically address the observational data on the benefits and risks of EVT for DVO, with a special focus in M2 middle cerebral artery occlusions. Finally, we will also discuss the design and methodology of ongoing RCTs that will provide definitive data on the safety and efficacy of EVT for AIS patients with DVO.