CORAL SPRINGS, Fla. -

When Jacob Chychrun hits the ice, the 13-year-old hockey player feels right at home.

"I've been playing since I was 5 or 6, and I'm really hoping one day to go pro like my dad," he said.

Like all contact sports, hockey carries a risk of head injury, something Jacob experienced firsthand early in the 2011 season.

"A guy came on the blind side and hit me and I hit my head on the ice," he said. "I didn't even remember coming off the ice.  I was talking to my dad, and he said, 'What happened?'  I said, 'I don't know.'  I really just wasn't aware of anything."

Jacob was later diagnosed with a concussion.

"What a concussion really is is a complex injury to the brain," said Dr. David Westerdahl, a sports medicine specialist with the Cleveland Clinic Florida.

Westerdahl said the injury isn't always obvious on an MRI or CAT scan, which is why parents and coaches need to know what to watch out for.

The warning signs can include headache, dizziness, nausea, sensitivity to light and noise, confusion and memory problems.

"Sometimes symptoms evolve. They might have mild symptoms within the first minutes to hours, but over the next 24 hours, they might have more of an evolving symptom pattern, and their findings might change, as well," Westerdahl said.

Westerdahl said the key to treating a concussion is allowing time for the brain to heal.

"We have a saying: 'When in doubt, sit them out,'" he said.

"I'm both a coach and parent, and as a former hockey player myself, I know that we have to take these incidents seriously," said Jeff Chychrun, Jacob's dad.  "We need to carefully evaluate these kids and make sure they're 100 percent before they're put back in the game."

Jacob knows that having had one concussion, he's at greater risk for a second injury, but he doesn't let that stop him from playing with a passion.

"I try to go out there and not worry about it, to just be myself out there," he said.