"Natasha Richardson fell in a beginners trail while taking a ski lesson at Station Mont Tremblant," the statement said. "She was accompanied by an experienced ski instructor who immediately called the ski patrol. She did not show any visible sign of injury, but the ski patrol followed strict procedures and brought her back to the bottom of the slope and insisted she should see a doctor.
"As an additional precautionary measure, the ski instructor as well as the ski patrol accompanied Mrs. Richardson to her hotel," the statement continued. "They again recommended she should be seen by a doctor. The ski instructor stayed with her at her hotel. Approximately an hour after the incident Mrs. Richardson was not feeling good. An ambulance was called and Mrs. Richardson was brought to the Centre Hospitalier Laurentien in Ste-Agathe and was later transferred to Hôpital du Sacre-Coeur."
A spokesperson for the resort noted Richardson was not wearing a helmet while skiing and didn't collide with anything when she fell.
But even absent an external injury, Flamm said, a tear in a blood vessel near the brain would be a prime candidate for the worsening headaches and, eventually, the loss of consciousness that Richardson experienced.
When bleeding occurs in the tissues surrounding the brain, the blood may become trapped between this covering and the brain itself. As the amount of blood in this space increases, so, too, does the pressure on the brain.
"Though the patient does not necessarily appear impaired at the beginning, as pressure builds up in the brain you can have a coma," Flamm said.
Faden agreed that, although unusual, these types of traumatic brain injury have been known to occur.
"With some cases of TBI, there is an immediate, significant period of unconsciousness, then a slow recovery," he said. "But this particular presentation does happen, even in milder forms of head injuries, though particularly in the elderly.
"You can imagine what happens when you compress the brain."
Faden said that Richardson's death should serve as a reminder to the public to take precautions against head injuries whenever possible.
"People don't realize how common this is," he said. "Every year, there are at least 2 million head injuries in the United States, and about 500,000 of these are serious enough for the emergency room."
He said that he believes the use of a helmet may have helped lessen the likelihood of a traumatic brain injury. Still, Flamm said there is little evidence in this case that a helmet would have warded off Richardson's injury.
"You can't be 100 percent safe in anything," he said.
To learn more about how to recognize serious head injuries, visit the Web site of the Brain Injury Association of America.
ABC News' Sharyn Alfonsi, Emily Friedman, Lindsay Goldwert and Luchina Fisher contributed to this report.