Former racing driver Michael Schumacher remains in a critical condition and is fighting for his life following a skiing accident in France.
The 44-year-old German suffered a severe head injury on Sunday while skiing off-piste in the resort of Meribel.
Medics have revealed that Schumacher would "certainly" not have survived the accident if he had not been wearing a helmet.
Doctors in Grenoble refused to speculate on the prognosis for the seven-time Formula One racing champion.
They confirmed that Schumacher had undergone one operation since the accident and was now in an induced coma in intensive care.
Professor Jean Francois Payen, speaking at a news conference at the University Hospital of Grenoble, said: "This accident was particularly serious and he was dealt with immediately and at our hospital he was immediately operated on after a brain scan.
"And then afterwards his condition is critical. As for cerebral care, all the recommended treatments have been introduced and for the moment we are not able to express ourselves with regards to Michael Schumacher's future."
He said the driver's helmet had protected him to a "certain extent" from the "very violent shock".
"Somebody who would have this kind of accident without a helmet certainly, he would not have got to here," he said.
Neurosurgeon Tony Belli added that the injury Schumacher suffered is likely to pose an ongoing risk as doctors attempt to reduce swelling and stem a potential brain bleed.
He said: "From what we know, he is in a critical state and in intensive care at the moment.
"It's likely he will be on a breathing machine with complex monitoring equipment around him and he's likely to be in a coma still.
"Initially, from what I gather, he was talking and trying to reassure people but then he became unconscious quite rapidly.
"That would suggest that he probably had brain swelling and that's something that can happen quite often - people initially seem to be OK, and then the brain begins to swell up and things get more serious."
The consultant at Queen Elizabeth Hospital in Birmingham told ITV: "You're dealing with a swollen brain, and often the brain bleeds quite easily.
"The brain is very friable and it obviously has to be handled with a lot of care, particularly when it's swollen - it can actually sustain further damage during the operation itself.
"The bleeding in itself could be quite serious because, unfortunately, when the brain has been bruised, it can carry on bleeding for quite some time during the surgery itself."