Identifying Intracranial Atherosclerotic Disease in Emergent Large Vessel Occlusion

Abstract Background Intracranial atherosclerotic disease (ICAD) represents a substantial proportion of large vessel occlusion (LVO) strokes refractory to mechanical thrombectomy, yet its diagnosis in the hyperacute setting remains challenging without direct vessel-wall imaging. Methods This narrative review is intended as a narrative and conceptual roadmap, acknowledging the inherent limitations of current methodologies for assessing ICAD in LVO patients. We evaluate clinical, pre-procedural imaging, angiographic, and intraprocedural features supporting a diagnosis of ICAD-related LVO, drawing on own experience and evidence from the literature. Articles were selected by authors for relevance to the conceptual framework. Randomized controlled trials, systematic reviews, and mechanistic pre-clinical studies were prioritized where available. Results Truncal occlusion morphology, fixed residual stenosis after thrombectomy, and early reocclusion emerge as the most reproducible high-specificity markers, while clinical risk-factor profile, absence of the susceptibility vessel sign, and collateral or perfusion patterns provide corroborating rather than standalone evidence. Discussion We propose a tiered diagnostic framework combining these markers to guide real-time decisions on bailout angioplasty or stenting, alongside a differential diagnosis of non-atherosclerotic mimics. Existing prediction scores show promising discriminative performance but remain largely unvalidated outside their Asian derivation cohorts. We propose illustrative enrollment criteria for future randomized trials, informed by recent studies. Conclusion Systematic, reproducible recognition of ICAD is essential to guide bailout treatment decisions and to enable rigorous evaluation of endovascular strategies tailored to this distinct stroke subtype.