Distal Vessel Occlusions in Acute Ischemic Stroke

Mechanical thrombectomy (MT) has revolutionized the treatment of acute ischemic stroke because of large vessel occlusion (LVO), but distal and medium vessel occlusions (DMVOs) remain a gray zone. DMVOs account for a substantial proportion of ischemic strokes and can cause long-term disability or death despite often presenting with only mild to moderate symptoms. Their biologic and anatomic diversity-including small vessel caliber, variable perfusion territories, collateral dependence, and complex access pathways-creates distinct patterns of natural history, treatment responsiveness, and procedural risk compared with proximal LVO. Recent randomized trials and meta-analyses, conducted in broadly defined DMVO populations, did not demonstrate functional benefit of endovascular therapy (EVT) over best medical therapy (BMT) and observed numerically higher rates of intracranial hemorrhage with MT. These neutral results have fueled skepticism and guideline recommendations against routine EVT for DMVO stroke; however, they coexist with emerging trial data suggesting that treatment effects may depend on refined patient selection and optimized, distal-specific techniques, as well as with registry findings indicating that many patients with DMVO remain disabled despite BMT. In this narrative, we provide an interpretative synthesis of the available evidence to argue that the apparent discrepancy between biologic plausibility and neutral trial results reflects, at least in part, heterogeneity of DMVO definitions and phenotypes, limitations of severity and outcome scales, anatomy- and device-related safety constraints, and the unique mechanics and biology of small vessel thrombus retrieval rather than an absence of biologic efficacy. We highlight clinical, imaging, anatomic, and thrombus-related features which may help identify subgroups more likely to benefit from distal reperfusion and discuss emerging technical and pharmacologic strategies-including DMVO-specific device adaptations, intraarterial thrombolysis, and hybrid reperfusion approaches-which aim to reduce mechanical trauma while preserving the advantages of timely recanalization. Together, these considerations support a shift from viewing distal MT as a failed extension of proximal EVT to recognizing DMVO stroke as a distinct syndrome that requires tailored selection, techniques, and outcome assessment.