This is the last part of the three-part series on concussions. Today’s story is about Second Impact Syndrome.

Football is a sport of brain-rattling collisions, and concussions have become common at every level of competition. But an uncommon condition associated with the aftermath of such injuries is often fatal for the youngest players.

Second Impact Syndrome occurs while the brain is recovering from an injury and suffers another blow. Because the brain is vulnerable after an initial injury, a relatively weak force can cause irreparable damage. If the brain’s ability to regulate blood flow is obstructed, a patient can die in as little as three minutes, according to sportsmd.com.

In 2008, Jaquan Waller, 16, was killed after playing in a high school football game in Greenville, N.C. A medical examiner attributed his death to Second Impact Syndrome.

The condition is more common among teenagers and children because their brains have not fully developed.

“It doesn’t happen to everyone that’s still symptomatic, but it does happen,” said Richard Rodenberg, a physician at Ohio State and Nationwide Children’s Sports Medicine. “And when it does happen, 50 percent of those kids statistically are at risk for death, and 100 percent of them will have a disability or suffer from permanent brain damage.”

The Centers for Disease Control and Prevention estimates that 1.6 million to 3.2 million concussions occur every year in sports and other recreational activities.

Second Impact Syndrome results when athletes sustain head injuries and one of three things happen: They don’t know they’ve been injured, they refuse to leave the game or they return to competition too soon.

The syndrome occurs when “a second head injury is sustained, either that day or in the few days shortly thereafter,” said Kelsey Logan, medical director of the OSU Sports Concussion Program. “Some athletes have died.”

Concussions can have serious consequences, especially for football players.

The New York Times reported that since 1997, at least 50 youth football players, high-school aged or younger, from 20 states have died or sustained serious head injuries on the field.

Although it’s hard to determine which athletes are in greatest danger of Second Impact Syndrome, dodging the disorder is not difficult.

“It’s really unknown who’s at risk for this and what the factors are that lead to death in those cases,” Logan said. “Fortunately, it’s also something that’s totally preventable if we can recognize the symptoms of concussions.”

Logan said concussion symptoms include chronic headaches, attention problems, short-term memory difficulties, sleeping problems and fatigue.

Although Second Impact Syndrome can be avoided, there are instances when the concussed athletes’ symptoms go unnoticed, or athletes aren’t correctly treated.

OSU athletics director Gene Smith said players are not always honest about their injuries.

The tough part is “getting the players to admit it,” Smith said. They say, “‘I’m a player. No disrespect, I didn’t come here to get a philosophy degree. I came here to go pro.’ That’s the mentality we get when they get to us.”

OSU club football team quarterback Bryan Thompson, who estimates he has suffered seven or eight concussions since he started playing football in the fourth grade, said he has played through a concussion.

“Once in high school during a game, I had an obvious concussion. I even walked toward the wrong sideline. As the trainer evaluated me, I sort of snapped out of my dementia. It was a close game, so I said, ‘I’m fine,’ and went back in,” Thompson said. “After the game, I went to the doctor and it ended up being one of the two major concussions I’ve had.”

Thompson, who had never heard of Second Impact Syndrome, said peer pressure can factor into playing though head injuries.

Playing with a concussion “was a heat-of-the-moment thing, and of course I wanted to stay in the game,” Thompson said. “But at the same time, a lot of people don’t look at concussions as serious injuries. They give it a negative spin and say, ‘Well, I know a ton of people that have played with concussions before, so why aren’t you playing?’ Then you feel more obligated to play.”

Doctors say that mentality is dangerous.

“That’s the scary aspect,” Rodenberg said, “when (athletes) hide their symptoms.”