MRI Evaluation of Stroke: Differentiating Haemorrhagic and Ischemic Pathologies

Abstract

Stroke remains one of the leading causes of death and long-term neurological disability worldwide. Differentiating ischemic stroke from haemorrhagic stroke is the first and most urgent imaging priority because management pathways differ substantially. Ischemic stroke may require intravenous thrombolysis, endovascular thrombectomy, antiplatelet therapy, or anticoagulation in selected cases, whereas haemorrhagic stroke requires urgent blood pressure control, reversal of anticoagulation when indicated, neurosurgical assessment, and prevention of hematoma expansion. Although computed tomography is widely used in emergency stroke pathways because of its rapid availability, magnetic resonance imaging provides superior tissue characterization and can identify early ischemia, blood products, vascular occlusion, perfusion abnormality, haemorrhagic transformation, and stroke mimics. Objective: This review summarizes the role of MRI in differentiating haemorrhagic and ischemic stroke, with emphasis on MRI sequences, temporal lesion evolution, diagnostic pitfalls, advanced imaging techniques, structured reporting, and clinical decision-making. Methods: Recent peer-reviewed literature, including original studies, meta-analyses, imaging-based stroke studies, and contemporary guidelines published within the last five years, was reviewed. Key MRI sequences discussed include diffusion-weighted imaging, apparent diffusion coefficient mapping, fluid-attenuated inversion recovery, gradient echo imaging, susceptibility-weighted imaging, perfusion MRI, arterial spin labeling, magnetic resonance angiography, and vessel wall imaging. Results: Diffusion-weighted imaging with ADC mapping remains the most sensitive MRI method for detecting acute ischemic injury, whereas GRE and SWI are central to identifying intracranial haemorrhage, microbleeds, superficial siderosis, thrombus susceptibility, and haemorrhagic transformation. FLAIR supports lesion-age assessment and DWI-FLAIR mismatch evaluation in unknown-onset stroke. Perfusion MRI and arterial spin labeling provide information about tissue-at-risk, delayed transit, collateral physiology, and post-recanalization haemodynamic changes. MRA detects large-vessel occlusion, stenosis, dissection, and vascular malformation, while vessel wall MRI improves etiological classification in selected patients. Conclusion: MRI is a highly valuable modality for differentiating ischemic and haemorrhagic stroke when performed using a rapid, structured, and treatment-oriented protocol. The most useful acute MRI protocol includes DWI/ADC, FLAIR, GRE or SWI, and MRA, with perfusion imaging, ASL, and vessel wall imaging added according to clinical need.