A CVA may be caused by any of the following: A piece of fatty plaque (debris) that is formed in a blood vessel breaks away and flows through the bloodstream going to the brain. The plaque blocks an artery which causes a stroke. This is called an embolic stroke. A thrombus (blood clot) formed in an artery (blood vessel) and blocked blood flow to the brain. This is called a thrombotic stroke. A torn artery in the brain, causing blood to spill out.