How does blood-pressure cause stroke?

In chronic hypertension the specific arterial lesions responsible for brain damage affect the small resistance arteries. The pathological characteristics of these lesions (notably the presence of microaneurysms, intramural fibrin, and lipid) and the location of lesions within the brain all suggest that they arise from mechanical distension, which destroys the integrity of the vessel and allows plasma insudation into the wall (lipohyalinosis), finally leading to occlusion or rupture. The process in analogous to the breakdown in vascular resistance and permeability which occurs in acute hypertension.