MICHAEL Schumacher remained in a critical condition in hospital on Monday as doctors admitted they could not tell whether he would recover from a skiing accident.

The seven-time Formula One champion is in an induced coma in intensive care at the University Hospital of Grenoble, having undergone brain surgery after hitting his head on a rock in a crash at the resort of Meribel in the French Alps on Sunday.

Doctors treating the 44-year-old German said at a press conference that it was too early to speculate on his prognosis and they were taking his fight for survival "hour by hour".

But they did reveal he would definitely not have survived had he not been wearing a helmet.

Chief anaesthesiologist professor Jean-Francois Payen said: "Taking into consideration the very violent shock, his helmet did protect him to a certain extent, of course.

"Somebody who would have this kind of accident without a helmet, certainly he would not have got to here."

He added: "For the moment we are not able to express ourselves with regard to Michael Schumacher's future.

"We are not currently able to talk about after-effects. We are talking about treatment and we are working hour by hour.

"Day and night we are at his bedside, but it is far too early to be able to say anything as far as prognosis is concerned."

Doctors said the brain scan Schumacher underwent on his arrival at the hospital showed "a great number of lesions".

The former racing driver is receiving treatment to reduce the pressure on the brain, with doctors describing his condition as "extremely serious".

Professor Stephan Chabardes, the neurosurgeon who operated on Schumacher, said: "The brain scan showed some intracranial haematoma (bleeding), but also some cerebral contusions and edema (swelling).

"We operated urgently to try and eliminate the haematoma. After the operation we saw that we had been able to eliminate the haematoma, but also sadly the appearance of various bilateral lesions and so therefore he was taken to intensive care to try to help him."

Professor Payen added: "His condition is critical as far as cerebral care. All the recommended treatments have been introduced."

He said he had only been operated on once and a second operation was at the moment not looking necessary.

Schumacher's body temperature is being kept at between 34 and 35 degrees. He is under general anaesthetic to reduce any external stimuli and ensure the flow of oxygen to his brain.

The doctors said it was "possible" his sporting background would help him to recover.

Given the seriousness of his injury, despite the fact he was wearing a helmet, they said the crash was likely to have taken place at high speed.

Schumacher's family - he has two children with his wife Corinna - are at his bedside.

Schumacher's spokeswoman Sabine Kehm issued a statement on behalf of the family thanking medics and well-wishers from across the world.

It read: "We would like to thank the medical team who we know do everything possible to help Michael.

"We would like to also thank the people from all around the world who have expressed their sympathy and sent their best wishes for Michael's recovery.

"We would like to ask the media to respect the privacy of us and our friends and thank them for their support."

Schumacher was with his 14-year-old son and had been skiing off-piste when the accident occurred around 11am on Sunday.

A medical evacuation helicopter arrived in less than 15 minutes to take him to hospital.

The doctors said Schumacher was initially "agitated" and his neurological state then deteriorated when he arrived at hospital in Moutiers. He was then quickly airlifted to the Grenoble hospital.

They said that going to Moutiers first was not detrimental to his health.

Schumacher retired from F1 for a second time in 2012 after a three-season comeback with Mercedes.

Schumacher, who also raced for Jordan, Benetton and Ferrari, won the last of his world titles in 2004.

He won two with Benetton in 1994 and 1995 before moving to Ferrari and winning five in a row from 2000. The German has 91 career wins.

His return to the sport with Mercedes after a spell in retirement was less successful. He managed just one podium finish in his three years with the team and a best end-of-season placing of eighth in 2011.

During his first period of retirement, in 2009, he was taken to hospital after a motorbike crash during testing at a circuit in Cartagena, Spain. He did not suffer serious injuries on that occasion.

Meribel, an upmarket resort, hosted the ice hockey and women's alpine skiing at the 1992 Winter Olympics.