An MRI Based Ischemic Stroke Classification - A Mechanism Oriented Approach.

Oxfordshire Community Stroke Project and Trial of Org 10172 in acute stroke treatment are the commonly used ischemic stroke classification systems at present. However, they underutilize the newer imaging technologies. Diffusion-weighted magnetic resonance imaging (DW-MRI) of the brain can detect the site and extent of infarcts accurately. From the MRI patterns, the mechanisms of ischemic stroke can be inferred. We propose to classify ischemic infarcts into the following types based on their DW-MRI appearance: cortical territorial infarcts, striatocapsular infarcts, superficial perforator infarcts, cortical and deep watershed infarcts, lacunar infarcts, long insular artery (LIA) infarcts, branch atheromatous disease (BAD) infarcts, corpus callosal infarcts, infratentorial infarcts, and unclassifiable infarcts. This DW-MRI-based classification of ischemic stroke is easy, fast, and mechanism oriented. A review of the literature reveals that cortical territorial, striatocapsular, and corpus callosal infarcts are associated with embolic sources and large artery intracranial atherosclerosis. Superficial perforator and LIA infarcts are also probably embolic. Watershed infarcts are frequently associated with severe carotid disease with microembolism or hemodynamic failure. Mechanisms of BAD infarcts include microatheroma, junctional plaque or a plaque within a parent artery blocking the orifice of a large, deep penetrating, or circumferential artery. Small lacunar infarcts are due to the lipohyalinosis of penetrating arteries. Types and mechanisms of infratentorial infarcts are similar to supratentorial infarcts. Such a classification system is useful for prognosticating acute stroke, arranging specific investigations, and planning strategies for secondary prevention and research.