Female Speaker: Meet Valerie Greene, you can't help but notice her energetic glow her zest for life. It's unimaginable that Valerie is the survivor of a massive stroke. It happened when she was just 31, an athletic, up-and-coming partner in a successful financial planning firm, in Winter Park, Florida. Valerie Greene: It was night and day. One day you're functioning at a very high level, you've got everything going for you and the next day you're in a hospital bed, having someone take you to the bathroom, you can't speak, you're paralyzed. It is a horrible, horrible thing. You feel like you are locked in your body. You can't make it move and do things you're accustomed to. In my case, it was just the most traumatizing, shocking experience I unfortunately had to go through. Female Speaker: The most common type of stroke occurs when a blood clot blocks one of the blood vessels serving the brain. Valerie's neurologist, Dr. Ira Goodman of Orlando Regional Medical Center, explains why this can cause so much damage so quickly. Dr. Ira J. Goodman: The brain needs blood. It supplies oxygen, it supplies sugar. If there is a blockage in the artery that supplies the sugar and the oxygen the brain cells die. The brain cells are very, very, very sensitive. If a brain cell goes for four to five minutes then it can cause severe damage, by ten minutes, it's irreversible damage. Female Speaker: The symptoms of stroke usually come on suddenly and vary depending on which part of the brain is affected. Common signs include numbness, tingling or loss of strength, especially on one side of the body. Confusion or slurred speech trouble seeing in one or both eyes, dizziness, loss of balance or difficulty walking or a severe headache with no known cause. Months before Valerie's devastating stroke, she had several excruciating headaches accompanied by nausea and dizziness. Although she was initially misdiagnosed with migraines and early multiple sclerosis symptoms, she had actually experienced a minor stroke, a precursor of what was to come. Valerie Greene: At first I was incredibly depressed, which I think is perfectly normal, natural. I was not sure why this would happen to me, I was healthy, I was young, I was successful. Female Speaker: Sometimes those at risk get a more subtle warning in the form of transient ischemic attack or TIA, often called a mini-stroke. A TIA is characterized by the same symptoms as stroke, but it's usually over after several minutes. That doesn't mean it should be ignored. A third of those who experience a TIA will go on to have a stroke. Dr. Ira J. Goodman: If you have a TIA, you get to emergency room immediately. Get worked up, because it's very, very possible the TIA can be a marker for the stroke. If you look in the right places, you might be able to prevent the stroke. And, again, it's much, much easier to prevent a stroke than to treat a stroke once its happened. Female Speaker: One reason treatment is so difficult is that like Valerie many patients don't realize they're having a stroke, and they get to the hospital too late to receive the most dramatically effective therapy. The first three hours are critical, according to Miami-based Baptist Hospital's Director of Rehabilitation, Dr. Brad Aiken. Dr. Brad Aiken: We're learning more about the acute treatment of a stroke. The biggest advance in recent years really has been in the use of TPA, which is a chemical used to dissolve blood clots, that's also been used in the treatment of heart attacks. It's now being used in some cases, in strokes, to try and dissolve the blood clot that's causing the stroke. To be effective, you have to get into the hospital it's got to be used within the first few hours of the stroke. Female Speaker: Only 10 percent of those who have a stroke recover completely, the rest face long-term disabilities ranging from mild to severe. 57-year-old Esther Kramer is learning to walk again after a stroke that affected her entire right side. Esther Kr