Healthy and active life possible

He is a professional athlete in the prime of life, a man paid handsomely to be a specimen of physical fitness.

So how could Tedy Bruschi suffer a mild stroke?

Strokes are usually a plight of aging, a consequence of arteries gone hard or a heart turned rickety. But they do happen to young adults, either because of bad genes or because of some traumatic event that causes a blood clot to form elsewhere in the body, shear off, and travel to the brain.

Bruschi, a Pro Bowl linebacker for the Super Bowl champion Patriots, left Massachusetts General Hospital yesterday, where he had arrived Wednesday complaining of persistent headaches, blurred vision, and numbness on his right side. Although appearing wobbly, Bruschi walked out of the hospital under his own power, accompanied by his wife, Heidi.

Neither Bruschi, 31, nor his physicians provided details of his condition or his prognosis. But neurologists not involved with his treatment said yesterday that young stroke patients can often look forward to a healthy, active life -- but not necessarily a life that involves the rough and tumble of the National Football League.

"It would depend on the treatment that someone requires and the kind of sport they're returning to," said Dr. Arthur Day, director of the Neurological Sports Injury Center at Brigham and Women's Hospital.

"They could return to bowling or they could return to baseball. But when you're talking about contact sports like football or hockey where people are trying to hit you and hurt you, then that's another thing."

Day has treated athletes who have suffered strokes as a result of injuries sustained while playing their sport, including a major league baseball player whom he declined to identify.

In those cases, an otherwise robust athlete might take a blow to the neck or the head with such ferocity that it bruises or kinks a major vessel such as the carotid artery, which snakes up the neck and into the brain. Blood begins clotting inside the vessel, growing so large that it eventually punctures the inner wall of the vessel and pops into the bloodstream.

When the clot is in the carotid artery, it travels freely.

"It's just like an interstate that runs through downtown Boston," Day explained. "The further you get away from downtown, the less lanes you need as people turn off to go home."

In the human body, those lanes -- blood vessels -- narrow as the clot travels deeper in the brain, until it can go no farther.

The signs that something is seriously wrong vary, depending on where the clot stalls.

"If it's the arteries that go to the back of your head, they might affect your vision," said Dr. Judith Hinchey, a neurologist at Caritas St. Elizabeth's Medical Center. "If it's the arteries that go to the left side of the brain, it might affect the ability to talk and to understand. If it's the artery to the front of the brain, it might affect the ability to move one side of your body."

With any acute medical condition, time is of the essence. Trauma physicians even have a term for that: the golden hour, the time in which treatment needs to be started to save somebody who has been shot, stabbed, or gravely injured in a car wreck.

For stroke patients, it's more like the golden three hours. That's because if doctors are able to figure out quickly enough whether a patient has had a stroke -- and, if so, what kind -- clot-busting medicine can be administered to dissolve the blockage before it produces devastating damage.

"The first thing we do is the patient history," Hinchey said. "Strokes happen suddenly. Boom. Your brain doesn't tolerate not getting blood, or it doesn't tolerate getting extra blood."

And those are the two possibilities with a stroke: Either it's caused by a blockage that impedes blood flow or from a vessel rupture that allows blood to gush into the brain.

Doctors use high-tech snapshots to determine what kind of stroke they're confronting.

If it's a rupture and the patient is young, it's typically blamed on a malformation in the vessel that results from a congenital quirk. Repairing it means placing a tiny clip at the site of the ballooning vessel so that the damaged part is put out of the way and then, possibly, packing the ballooned part with tiny coils so that it cannot fill with blood.

If it's a clot, that blockage could be the byproduct of a faulty heart or a propensity for the patient's blood to thicken -- or the result of trauma to an artery somewhere else in the body.

Patients with heart disease can form clots and those clots can go to the brain. Another possibility is that the patient has a condition that causes blood to coagulate so efficiently that it clots. But both of those scenarios, doctors said, are rare in younger patients.

That leaves the possibility of a clot resulting from an injury.

"There can be a kind of stroke related to athletics and that's one where the athlete receives a direct blow, like a helmet that hits his neck," Day said.

But, Day said, elite athletes are typically in such good shape that they can tolerate such assaults.

"Their arteries are strong and they're elastic," Day said. "If you were talking about a 60- or 70-year-old and you were hitting them on the head, it might be different."

If stroke patients get to the hospital swiftly enough -- usually within three to six hours -- doctors can give them a drug called tPA that's delivered either by an intravenous tube or directly to the clot. The prognosis for such patients, neurologists said, is often quite good.

But the calculus of recovery can be starkly different for a superstar athlete than for the average patient. Doctors know that having one stroke can put patients at risk for having subsequent strokes.

Day said that if repeated jarring from tackling would endanger a patient's healing, "then we would tell them don't do it. Then they have to decide whether they want to listen to you or not. They may decide a day with the Dallas Cowboys is worth all the arguments I can give them."

Stephen Smith can be reached at stsmith@globe.com.