The German racing great entered the new year in an induced coma and a critical condition, with his family at his bedside in the French Alpine city of Grenoble and doctors unsure of his future.
The 44-year-old's fight for survival after he fell and slammed his head on a rock while off-piste skiing on Sunday has shocked legions of sports stars and fans used to seeing him brave death on the racing tracks.
"At the moment, he is stable," the seven-time world champion's manager Sabine Kehm told reporters massed outside the hospital in Grenoble on
Wednesday, in a brief update before heading back inside.
Initially described as serious but not life-threatening after the accident in the upmarket resort of Meribel, Schumacher's condition rapidly deteriorated and by Sunday evening, doctors said he was in critical condition and had undergone an emergency operation.
On Tuesday, they said a slight improvement in his condition had allowed them to perform a second nearly two-hour long procedure to remove bleeding in the brain, but warned he was "not out of danger" yet.
"We cannot speculate on the future," said Jean-Francois Payen, head of the intensive care unit at the hospital. "We cannot say he is out of danger but we have gained some time."
Doctors have so far ruled out any transfer from the hospital, which they say would be "dangerous".
But they have pointed out that Schumacher, due to turn 45 on January 3, has age and physical fitness on his side.
He has been put in a medically induced coma to spur recovery. His temperature has also been reduced to around 35 degrees Celsius (95 degrees Fahrenheit) to reduce swelling.
By being unconscious, the brain is also switched off to sounds, light and other triggers that cause the organ to use up oxygen as it processes the stimuli.
It is as yet unclear exactly how the accident happened, but a source close to a probe into the incident told AFP that Schumacher's helmet, which medics say saved his life, had been smashed "in two" by the impact.
Kehm told journalists Tuesday that Schumacher was skiing "with a small group of friends" as well as his 14-year-old son Mick.
She said he was not skiing at high speed when the accident happened.
"He seems to have hit a rock as he took a turn. It was a chain of unfortunate circumstances."
Kehm added that the accident could have happened even "at 10 kilometres (six miles) per hour" and took place during "a normal turning manoeuvre".
Schumacher's condition has attracted attention from around the world and several people have tried to sneak through the hospital and approach the former racer, she said.
"There apparently was a person dressed up as a priest, who tried to get near Michael. I am asking everyone to let the doctors work and leave the family to spend peaceful time with Michael."
Asked whether the priest was a journalist, she said: "It's what I was told… We have clearly noted that people are trying to get beyond the press room here in the clinic. It's revolting, in my opinion."
Schumacher, who won the last of his world titles in 2004, towered over the sport since his debut in 1991, winning more Formula One world titles and races than any other.
He had a record 91 wins and is one of only two men to race in 300 grands prix.
His duels in his heyday with Damon Hill and Jacques Villeneuve, fired by an unquenchable competitive spirit, have gone down in Formula One lore.
Born in January 1969 near Cologne, Germany, his father ran a local go-kart track where his mother worked in the canteen.
By 1987, Schumacher was the German and European go-kart champion and was soon racing professionally. In 1991 he burst into Formula One by qualifying seventh in his debut race in Belgium and a year later, he won his first Formula One grand prix.
He joined Ferrari in 1996 and went from strength to strength over the next decade, dominating the podium, before retiring aged 37.
But he could not resist the lure of the track and in 2010 he came out of retirement, signing a deal with Mercedes before quitting for good in 2012.