At first, Natasha Richardson felt fine after she took a spill on a Canadian ski slope. But that's not unusual for people who suffer traumatic head injuries like the one that killed the actor.
The injury produced what is often called a "walk and die" syndrome, which is usually due to delayed bleeding from an artery in the brain, said Dr. Christopher Giza, a neurologist at the University of California, Los Angeles' Brain Injury Research Center.
An autopsy Thursday showed that the 45-year-old actor suffered a blow to the head Monday which caused bleeding between the skull and the membrane that covers the brain. Called an epidural hematoma, it's often caused by a skull fracture. Doctors said she might have survived had she received immediate treatment.
"This is a very treatable condition if you're aware of what the problem is and the patient is quickly transferred to a hospital," said Dr. Keith Siller of New York University Langone Medical Center. "But there is very little time to correct this."
In some cases, the patients, like Richardson, appear normal immediately after the injury, walking and talking as though nothing happened. But symptoms can develop within an hour, causing impaired speech and vision and leading to a coma.
Doctors say sometimes patients with brain injuries have what's called a "lucid interval" where they act fine for an hour or more as the brain slowly, silently swells or bleeds. Later, back at her hotel, Richardson became ill, complained of a headache, and was taken to a hospital. She died Wednesday in New York.
Lyne Lortie, a spokeswoman for the Mont Tremblant ski resort in the Laurentian Hills north of Montreal, said Richardson had fallen during a beginner's lesson. She was not wearing a helmet.
"It was a normal fall; she didn't hit anyone or anything," Lortie said. "She didn't show any signs of injury; she was talking and she seemed all right."
As a precaution, when she left the slopes, Richardson was accompanied by a member of the resort's ski patrol and her instructor, who then remained with her at a hotel.
When she started having headaches about an hour later, she was taken by ambulance to a hospital.
Such injuries are not common, "but they do occur, even in patients that have been evaluated by a CT scan," said Dr. Keith Black, a neurosurgeon at Cedars-Sinai Medical Center.
Because of that lucid interval, doctors always tell patients who seem okay after a brain injury to have someone keep a close eye on them, in case symptoms emerge.
Symptoms — headache; loss of consciousness; vomiting; problems seeing, speaking or moving; confusion; drainage of a clear fluid from the nose or mouth — appear after enough pressure builds in the skull. By then it's an emergency.
"Once you have more swelling, it causes more trauma which causes more swelling," said Dr. Edward Aulisi, neurosurgery chief at Washington Hospital Center in the nation's capital. "It's a vicious cycle because everything's inside a closed space."
Pressure can force the brain downward to press on the brain stem that controls breathing and other vital functions, causing coma or death. Frequently, surgeons cut off a portion of the skull to give the brain room to swell. Or they drain the blood or remove clots that formed.
Details of Richardson's treatment have not been disclosed.
One lesson can be taken from the episode: Skiers, like skaters, bicyclists and other sportsmen, should wear helmets to prevent injury.
Quebec is considering making helmets mandatory on ski slopes.
Information from the Associated Press, New York Times and Los Angeles Times was used in this report.