A stroke happens when blood flow to the brain stops. There are two different kinds of stroke. The most common is an ischemic stroke, caused by a blood clot that blocks a blood vessel or artery in the brain. The other, less common, is a hemorrhagic stroke, caused when a blood vessel in the brain ruptures and spills blood into the surrounding tissue. Brain cells in the area begin to die, either because they stop getting the oxygen and nutrients they need to function, or they are killed by the rupt...