Malignant middle cerebral artery infarction revealing atrial fibrillation: A Multimodal imaging case of M1 occlusion treated with decompressive craniectomy.

Malignant middle cerebral artery (MCA) infarction represents a severe form of ischemic stroke characterized by extensive cerebral ischemia, rapid development of cerebral edema, and a high risk of fatal brain herniation. Atrial fibrillation is a major cause of cardioembolic stroke and is frequently associated with large vessel occlusion and poor outcomes. We report the case of a 70-year-old woman with poorly controlled hypertension who presented with acute left-sided hemiplegia and altered consciousness with a delay of approximately 48 hours from symptom onset. Electrocardiography revealed previously undiagnosed atrial fibrillation with rapid ventricular response. Initial non-contrast brain computed tomography demonstrated early ischemic changes involving the right MCA territory with signs of mass effect. Multimodal magnetic resonance imaging confirmed a large cortico-subcortical infarction involving more than 50% of the right MCA territory, with marked diffusion restriction and no diffusion-FLAIR mismatch, indicating a completed infarction. MR angiography demonstrated occlusion of the M1 segment of the right MCA. Imaging also revealed significant cerebral edema with a midline shift of 12 mm and early signs of subfalcine herniation. Despite intensive care management and urgent decompressive hemicraniectomy, the patient showed no neurological improvement and had a fatal outcome. This case highlights the crucial role of multimodal imaging in the diagnosis and prognostic assessment of malignant MCA infarction. Large vessel occlusion, extensive infarct volume, and significant mass effect are key imaging features associated with poor outcome. Early detection and appropriate anticoagulation of atrial fibrillation remain essential to prevent severe cardioembolic stroke.