The autopsy on Thursday suggests that the fall tore an artery inside Ms. Richardsonâ€™s skull, resulting in bleeding in an area between the skull bone and the lining covering the brain, called the dura matter. Ms. Richardsonâ€™s death was ruled an accident, said Ellen Borakove, a spokeswoman for the medical examinerâ€™s office. She added that the medical examinerâ€™s office did not have information on whether Ms. Richardson was an organ donor.
The official cause of death was an epidural hematoma. A hematoma is a collection of blood.
The description of Ms. Richardsonâ€™s behavior after she fell fits in with the initially subtle symptoms of the condition, said a brain surgeon not involved in her care, Dr. David J. Langer, the director of cerebrovascular neurosurgery at St. Lukeâ€™s-Roosevelt, Beth Israel and Long Island College Hospital, and an assistant professor at the Albert Einstein College of Medicine at Yeshiva University.
At first, the 45-year-old Ms. Richardson was up and about, acting normally, but she soon developed a crushing headache.
â€śPeople classically have a lucid interval, like what she had,â€ť Dr. Langer said, adding that symptoms develop as the bleeding continues and the clot grows big enough to press on the brain. Epidural hematomas do show up on CT scans, and surgery is needed quickly to relieve the pressure, remove the clot and stop the bleeding. Ms. Richardsonâ€™s sudden death left not only sadness â€” Broadway will dim the marquee lights before its 8 p.m. performances on Thursday in her memory â€” but unsettling questions about how a seemingly minor accident could have caused such a grave injury.
A spokeswoman for the ski resort, Mont Tremblant, said Ms. Richardson â€” who was not wearing a helmet â€” fell on soft snow, did not appear to have hit her head, did not lose consciousness and joked about falling. But she immediately stopped skiing and returned to her hotel room, accompanied by her instructor and a member of the ski patrol. It is not clear whether she needed their help.
The spokeswoman said that the ski patroller advised Ms. Richardson to see a doctor, but that she declined to do so. The reason for that advice is not known. But people who take minor spills on ski slopes are not usually urged to see a doctor unless they are showing some sign of an injury.
About an hour after the fall, an ambulance was called and Ms. Richardson was taken to a small hospital about 20 minutes from the resort â€” one that has a CT scanner but not an MRI scanner. In addition, a spokesman there said, the hospital does not treat trauma cases, but stabilizes patients and then sends them to a larger hospital.
A few hours later, at about 5 p.m., Ms. Richardson was taken by ambulance to a larger hospital, HĂ´pital du Sacre-Coeur de Montreal, about 50 miles away. Citing Quebecâ€™s privacy laws, hospital officials declined to describe her condition or say what tests or treatments she received there.
On Tuesday afternoon, about 24 hours after she fell, an ambulance took her from the Montreal hospital to the airport, from which she was flown to New York. She was then taken to Lenox Hill Hospital, where she died the next day.
The resort had no immediate comment on the medical examinerâ€™s report of Ms. Richardsonâ€™s cause of death, but released a statement earlier on Thursday.
â€śOut of respect for the family, and their request for privacy, we will not comment further,â€ť spokeswoman Lyne Lortie said.
In addition, it said its staff â€śintends to fully cooperate with any resulting investigations.â€ť