Natasha Richardson, 45, was alert and conversational after she fell and bumped her head at the end of a skiing lesson on Monday.
Back in her hotel room, just an hour later, she developed a severe headache and her condition quickly took a turn for the worse. By Tuesday, she was flown from Montreal to Lenox Hill Hospital in New York City in critical condition.
She was reported to be brain dead and on a ventilator when she was detached from life support late Wednesday and died.
The fact that Richardson was not wearing a helmet may or may not have made a difference in the gravity of her injury say experts. In fact, traumatic brain injury is more common than most people think.
In the United States, more than 1.5 people suffer from a brain injury each year.