Dr. Mark Johnson of the University of Texas Southwestern Medical Center in Dallas says bleeding or the formation of blood clots in the brain kills brain cells by cutting off oxygen. He says treatment must begin within three hours to be effective.
Symptoms of stroke include: numbness, dizziness, mental confusion, vision problems, trouble with coordination or severe headache -- all of which come on suddenly.
Johnson says if stroke is suspected, try this simple three-question test:
-- Ask the person to smile.
-- Ask the person to raise both arms.
-- Ask the person to say a simple sentence, such as "My name is ... "
"If the individual is unable to do any of these, call 911 immediately," Johnson says in a statement.
"Several factors can increase the risk of stroke, including: smoking, high blood pressure, heart disease, diabetes and high cholesterol. Controlling those can decrease your risk of stroke."
Avril Lavigne denies racism in 'Hello Kitty' music video
Jeb Bush 'thinking about running for president' in 2016