Contraindications to endovascular treatment in acute ischemic stroke: Where evidence ends and structured reasoning begins

Endovascular treatment (EVT) is the standard of care for acute ischemic stroke caused by large-vessel occlusion within 24 hours from symptom onset. However, many conditions commonly labeled as “contraindications” reflect the absence of evidence rather than evidence of harm. This review reframes contraindication as the boundary of an indication envelope and proposes a structured framework to navigate it. We performed a narrative review of six major gray zones in EVT decision-making: anterior circulation large-vessel occlusion with mild symptoms, established large ischemic core, frailty and biological reserve, distal and medium vessel occlusion, basilar artery occlusion with mild symptoms and contraindications inherited from exclusion criteria of seminal trials. Imaging biomarkers, including core volume, net water uptake and cerebral blood volume index, may help distinguish beneficial from futile or harmful reperfusion at the boundaries of each domain. Recent evidence supports an expansion of EVT indications but does not eliminate upper or lower boundaries of benefit. Large-core trials demonstrate benefit yet suggest futility in very extensive infarctions. Data in minor stroke and distal occlusions show equipoise or potential harm with indiscriminate intervention. Frailty and biological reserve modify treatment effect independently of chronological age. Preserved relative treatment effects may coexist with negligible absolute benefit, requiring explicit shared decision-making. Where categorical limits give way to individualized judgment, the field will mature not only by expanding trial evidence but by reducing unwarranted variability and cognitive bias through center-specific standard operating procedures, supported by audit-and-feedback loops and longitudinal outcome tracking.