Natasha Richardson’s sudden death in 2009 was upsetting, in part, because after falling during a ski lesson, she allegedly felt so well that she declined medical attention that could have saved her. And yet, experts say, this short period of lucidity between a blow to the head and collapse is a known but rare symptom of an epidural hematoma — the cause of Richardson’s death, as pronounced by the New York medical examiner.

What is an epidural hematoma, and how can friends and family of an injured person recognize its symptoms in time to call 911 and get life-saving medical attention?

A dangerous blood clot

An epidural hematoma is a clot of blood between the skull and the dura — a tough layer of matter that covers the brain and spine. The clot occurs when a person has been hit in the head in such a way that an artery is ruptured. (This usually, but not always, happens with a skull fracture.)

“The bleeding is almost always arterial, which is high pressure,” says Steven Giannotta, M.D., professor and chair of neurological surgery at the Keck School of Medicine of USC. “The most common artery to be injured is the middle meningeal, which is torn when the skull is fractured. This artery is on the side of the head by the temple,” says Giannotta.

Because the area above the ear at the temple is the thinnest bone in the head, and next to an artery, it’s a vulnerable spot. “The location of the impact can be important in determining whether an epidural occurs,” he says.

In a similar kind of injury, called a subdural hematoma, a torn vein causes bleeding between the dura and the brain. After being hit in the head, a person who is suffering from an epidural or subdural hematoma may not experience immediate symptoms. But if an artery or vein has been torn, blood will gradually gather in an area where there is very little space, putting more and more pressure on the brain.

In an epidural hematoma, the temporal lobe on the side of the clot gets pushed down, explains Giannotta, and part of it will touch a nerve coming out of the brainstem that affects pupil dilation. The more this pressure continues, the more devastating the brain damage.

“As the clot grows, the pressure inside the head gets higher, squashing the brain. This causes lethargy, sleepiness and ultimately coma,” he says. “At this point, treatment becomes an emergency and if the clot is not removed quickly, the patient usually dies or is vegetative.”

Another kind of dangerous clot that can form as a result of a blow to the head is an intracerebral hematoma, when bleeding occurs within the brain. It may be necessary for a neurosurgeon to perform emergency surgery to remove a clot in order to reduce pressure on the brain.

This kind of injury can happen to anyone, of course, but people who are more at risk of developing a brain hematoma are those who are taking blood thinners.

“Blood thinners, especially coumadin, can increase the likelihood of a clot after a head bump,” says Giannotta. “This is usually in older folks — the ones that need coumadin — and usually the clot is a subdural.”

Symptoms to watch for

Anyone who goes unconscious after being hit in the head should be taken to a hospital emergency room immediately. “It takes time for blood clots to form, so epidurals and subdurals can cause delayed symptoms,” says Giannotta.

Even if the injured person remains conscious, he or she should be watched carefully. Symptoms to look for include a severe headache, nausea, sudden weakness on one side of the body, seizures, sleepiness and, of course, loss of consciousness.

“You should go [to the hospital emergency room] if symptoms either persist or get worse,” says Giannotta.

In an emergency room, the injured person will be given a CT scan — an X-ray of the brain — so that doctors can look for a skull fracture and identify developing blood clots.

Preventing brain injury

Falls and car accidents account for almost half of all traumatic brain injuries, according to the Centers for Disease Control and Prevention. An important way to prevent such injuries is to wear a sturdy helmet while bike riding, skate boarding, skiing or scootering.

In sports, athletes should wear appropriate head gear. Natasha Richardson reportedly was not wearing a helmet while she was skiing, which is not uncommon for many skiers. Obviously, wearing a seat belt in cars can reduce the chance of sustaining a serious brain injury in a crash.

Awareness can save lives too. Because of Richardson’s death, the general public is now acutely aware of the fact that even a relatively mild bump on the head can have devastating consequences. Watching for symptoms and making a trip to the emergency room are key to survival.