introduction about stroke

Leukoaraiosis (LA) is a descriptive term used to describe neuroimaging findings of diffuse hemispheric white matter abnormalities mainly characterized by loss of myelin and/or ischemic injury.1,2 The exact cause and pathophysiology of LA remain under active investigation, and most working definitions are operational in nature with numerous outstanding questions regarding the precise mechanisms of its occurrence and prognostic implications. LA exhibits a distinct pattern of distribution. It primarily occurs in the periventricular white matter and regularly spares the convolutional white matter, U-fibers, corpus callosum, internal capsule, anterior commissure, and the white matter of the brain stem.1 It is of note that periventricular white matter has its distinct blood supply characterized by multiple, parallel, penetrating, small arteries (100 to 170 µm in diameter) that arise from the pial vessels at almost right angles and run in a straight line toward the lateral ventricle.3 Arteries that supply the cortex and adjacent white matter, on the other hand, are often parallel to the cortical surface and exhibit fountain-like frequent ramifications.
In LA, the walls of penetrating arteries of the white matter are characteristically thickened and hyalinized. There is often arteriosclerotic narrowing, elongation, and tortuosity, yet occult occlusion or severe stenosis is rare.1,4 In addition, in brains with LA, the vascular density is diminished to approximately four fifths that of a normal brain.5 Furthermore, arteriosclerotic penetrating arteries in LA exhibit an inability to dilate in response to reduced blood flow.6 The cumulative effect of these factors is that the baseline cerebral blood flow in the white matter of brains with LA is depressed.7 It is, therefore, plausible to consider that compromised tissue perfusion at the macro- and microvascular level in LA can result in adverse tissue outcome in acute cerebral ischemia. As an initial investigation into this question, we sought to determine the correlation between LA volume and the proportion of initially ischemic but eventually infarcted tissue in human acute ischemic stroke.