Strokes can damage brain tissue in the outer part of the brain (the cortex) or deeper structures in the brain underneath the cortex. A stroke in a deep area of the brain (for example, a stroke in the thalamus, the basal ganglia or pons) is called a lacunar stroke. These deeper structures receive their blood flow through a unique set of arteries. Because of the characteristics of these arteries, lacunar strokes happen a little bit differently from other strokes.
A lacunar stroke occurs when one of the arteries that provide blood to the brain's deep structures is blocked. These arteries are small, and are uniquely vulnerable. Unlike most arteries, which gradually taper to a smaller size, the arteries of a lacunar stroke branch directly off of a large, high-pressure, heavily muscled main artery. High blood pressure (hypertension) can lead to lacunar strokes because it causes a pounding pulse. Since the arteries don't gradually taper down in their size, high blood pressure can directly damage these arteries. High blood pressure also can cause atherosclerosis, a condition in which fatty deposits (plaques) build up along the walls of blood vessels. When atherosclerosis is present, a clot can form inside of one of these small arteries, blocking blood flow in the artery.
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