A stroke is caused by a blockage of blood vessels in your brain. When your brain tissue isn't provided with blood it will start to die. Blood provides oxygen and nutrients and carries away waste. The location of the blood vessel blockage can determine what parts of your brain might be affected. Depending on what connections are severed, paralysis can result. If the stroke occurs on one side of the brain, paralysis may occur only on one side and is called hemiplegia. If the stroke occurs in the brain stem (the bottom part of the brain) it can cause paralysis on both sides of the body as well as affect functions such as breathing, swallowing, speech, etc.