Gracie Hussey was just 7 when she had her first concussion. In a youth soccer match, she was trying to head the ball into the goal when she collided with another player.
Her mother, Beth, figures there were other concussions along the way but the worst came five years later, when Gracie crashed onto artificial turf, slamming the back of her head.
Now 15, Gracie can no longer play soccer. She has headaches, suffers from inexplicable nausea and several times a day she feels like she's about to pass out.
''I had concussion symptoms all the time, but I didn't really know what they were so I wouldn't say anything,'' she said recently from her home in Memphis, Tennessee.