03/19/2009 at 06:30 PM EDT
Natasha Richardson died from a blunt impact to her head
, which caused internal bleeding in her brain. The actress, 45, fell
during a skiing lesson Monday before her death Wednesday.
Why did a fall, which caused no visible signs of injury, cause the actress to die?
PEOPLE talks to Dr. Gail Rosseau, Chief of Surgery at the Neurologic and Orthopedic Hospital of Chicago, about how why an epidural hematoma – the pool of accumulated blood in the brain – can be fatal, and what can be done to avoid such an injury. Why is an epidural hematoma deadly?
If you have an injury to a leg, it can swell as big as the room you are in. What's unique to the brain is the problem of having the skull all the way around it. Swelling has nowhere to go. The heart keeps beating and it can't get blood to the brain anymore. The brain is starved of oxygen and that is what brain death means.
How often is it deadly?
We don't have good data on it. It is one of the most feared injuries because it can be rapidly fatal. Time is of the essence. For surgeons, it can be satisfying, because you can completely cure it if the brain isn't injured. In Natasha Richardson’s case, [the medical examiner] didn't comment on the degree of injury within the brain.
What should you do if you hit your head?
Certain flags [such as] headache, nausea, dizziness and a change in consciousness are signs to get to the hospital.
Is there anything could Natasha Richardson have done to avoid the injury?
Number one, and most importantly, worn a helmet. Expert skiers wear them and beginners don't by a factor of more than 2-to-1. This notion that it's a baby hill, you don't need one, is not a logical argument. (According to the American Association of Neurological Surgeons, 1.5 million people suffered brain injuries in 2007, of which 10,419 occurred during skiing or snowboarding accidents.
Could Natasha have been saved?
We can't answer that. She could have probably been saved by a helmet, but even then we don't know for sure.