A stroke is death of brain tissue due to either bleeding into the brain or interruption of blood flow to an area of the brain. In the adult, the most common cause of stroke is the interruption of blood flow. This can occur in situ at the location of the stroke within the brain due to vascular disease or it can be a result of the passage or embolization of particulate matter from arteries in the neck, the large aorta within the chest, or the heart itself. This particular matter can be clotted blood or fragmented bits of cholesterol. Stroke is the most common complication related to longstanding, poorly controlled high blood pressure or hypertension.