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Wear your helmet!

Ah, summer! Season of baseball, bike rides, barbecues—and head injuries. There's nothing like warm weather to get people outside and active, and nothing like activity to fill up an emergency room.

But when does a bump on the head require immediate medical attention? ActressNatasha Richardson appeared to be fine after a skiing accident earlier this year; an hour later she was unconscious, and the next day she was dead.

The newspapers called it "Talk and Die" syndrome. According to David Good, M.D., head of neurology at Penn State's Hershey College of Medicine, this condition is usually caused by a particular head injury called epidural hematoma.

"Epidural hematoma is due to a fracture of the temporal bone, just in front of the ear," Good explains. "The temporal bone is thin compared to the rest of the skull, and if you bump it, it tends to fracture more easily. The problem is there's an artery that lies just under the bone."

This vulnerable artery—called the middle meningeal—carries blood to the scalp. If it is damaged, the bleeding can be swift and severe. "This is truly a medical emergency," says Good. "You can't wait three or four hours to treat it."

The middle meningeal artery is not located in the brain itself, he notes, but rather outside the dura, a thick membrane that surrounds the organ. "If damaged, it bleeds into what's called the epidural space, outside the dura, so there are no immediate symptoms." As the hemorrhage grows, however, the dura pushes in against the brain, and the brain becomes compressed.

Until that compression occurs, the injured person may seem to be okay, hence the "talk" in "Talk and Die." Says Good, "The person may have a headache and they may briefly lose consciousness, but then they'll be awake and they'll talk and seem fairly normal for a period of time—anywhere from five minutes to as much as an hour." Eventually, however, the sufferer becomes confused, and slowly lapses into a coma. "As the pressure builds in the brain," Good explains, "the person becomes unresponsive, and eventually the bleeding puts pressure on critical centers of the brain like the brain stem, and this can cause death."

As grim as that may sound, the news is not all bad. Because the bleeding occurs outside the brain, Good says, it does not directly damage brain tissue. "If a person gets immediate medical care to drain the blood, he or she will survive, and survive with no lasting effects because the brain itself is not injured. So the key is to get immediately to an emergency department."

Over a million people annually are treated in U.S. hospitals for brain injuries, with 50,000 deaths per year. Cycling leads the pack among sports-related causes, sending an estimated 65,000 people to the emergency room each year. Children age 14 and under are at greatest risk of sustaining such traumas, while people over 75 are most likely to die from them.

But how do you distinguish a relatively harmless bump on the head from a potentially life-threatening situation? Good agrees that it's difficult. "Concussions are common. And the vast majority of people who have concussions don't have any long-term effects. But if you get knocked unconscious, it is probably a good idea to be evaluated at the emergency room just to be sure, even though 99 percent aren't going to be serious."

After any head injury, he adds, it's important to be watchful. "If a person seems to deteriorate, or they become confused or disoriented or less responsive, it is absolutely critical that they go immediately to a hospital."

Of course, there are things we can do to prevent trauma from occurring in the first place. "Helmets will help, no question about it. Helmets for biking, hockey, football—anything that's a contact sport. Even soccer, though they're not popular."

Can you sustain a head injury even though you wear a helmet? "Sure," notes Good, "it happens." "But I think your chances are much less."

David Good, M.D., is chair of the neurology department at the Penn State Milton S. Hershey College of Medicine. You can reach him at dcg14@psu.edu.