Stroke Mechanisms

Recent advances in neuroimaging technologies, such as diffusion weighted magnetic resonance imaging (MRI), perfusion weighted computed tomography (CT)/MRI, MR/CT angiography and Doppler ultrasonography allow us to determine the mechanisms of stroke and transient ischemic attack. In addition, high-resolution vessel wall MRI is nowadays increasingly used to understand the stroke mechanism in patients with intracranial atherosclerosis. Artery to artery embolism, hypoperfusion and the combination of the two are the important stroke mechanisms in patients with extracranial atherosclerosis. In addition to the above two, branch occlusion and in-situ thrombotic occlusion are important stroke mechanisms in patients with intracranial atherosclerosis. Branch occlusion leads to subcortical or brainstem infarcts indistinguishable from infarcts caused by small artery disease. In-situ thrombotic occlusion leads to larger territorial infarcts. However, whole territory infarcts are uncommon due to relatively well developed collateral circulation in these patients. The treatment strategy should be based on the correct understanding of the stroke mechanism in individual patients.