The assumption that a ticking clock alone should govern stroke treatment decisions is now giving way to a more nuanced, biology-driven framework — one with direct implications for millions of patients who arrive outside classical treatment windows or with uncertain symptom onset.
This review in JMRI synthesizes the transition from rigid time-based reperfusion protocols to imaging-guided, tissue-based triage in acute ischemic stroke. Non-contrast CT and CT angiography remain the practical frontline tools — fast, widely accessible, and sufficient for initial decision-making — but MRI contributes layered biological detail that CT cannot match. Diffusion-weighted imaging (DWI) detects cytotoxic edema within minutes without contrast agents, while DWI-FLAIR mismatch functions as a tissue clock, enabling thrombolysis decisions in patients with unknown onset. Susceptibility-weighted imaging (SWI) refines thrombus characterization, and MRI's immunity to posterior fossa beam-hardening artifact makes it superior for vertebrobasilar strokes. The review also highlights four converging trends: extending mechanical thrombectomy eligibility into large-core infarctions, broadening thrombolysis via tissue-based patient selection, advancing recanalization protocols for posterior-circulation and distal-vessel occlusions, and streamlining workflows through rapid MRI sequences, quantitative CT biomarkers, and AI-assisted triage.
This synthesis arrives at a pivotal moment. Landmark trials — including DAWN, DEFUSE-3, and SELECT2 — have already established that salvageable penumbral tissue, not elapsed hours, is the decisive treatment variable. However, the review's acknowledgment of recent negative trials is equally important: it demarcates zones where aggressive intervention transitions from benefit to harm, a critically underemphasized finding in stroke literature. The emergence of low-field portable MRI represents a potentially democratizing development, extending tissue-based decision-making beyond tertiary centers to resource-limited settings. For a health-conscious readership, the practical signal is that access to advanced neuroimaging — and the institutional expertise to interpret it — increasingly determines who receives optimal acute stroke care. This review is confirmatory and synthesizing rather than paradigm-shifting on its own, but it offers valuable consolidation of a rapidly evolving evidence base.