A stroke, or cerebrovascular accident (CVA), occurs when blood supply to part of the brain is disrupted, causing brain cells to die. When blood flow to the brain is impaired, oxygen and glucose cannot be delivered to the brain. A stroke occurs when the arterial blood flow leading to or in the brain becomes blocked or a blood vessel in the brain ruptures. Blood carries oxygen and nutrients to the neurons (nerve cells) in the brain, so when the blood flow stops, the cells begin to die. As a result, the functions of the body controlled by the nerve cells can lose their ability to function.