LiveScience.com - Stroke is the number three killer in the United States, affecting almost 800,000 people each year, according to the National Stroke Association. These "brain attacks" occur when blood flow to the brain is interrupted (an ischemic stroke) or when a blood vessel in the brain leaks or bursts (a hemorrhagic stroke). For 144,000 people each year, the result is death. Hundreds of thousands of others are left with long-term disabilities.