Hopes and prayers
In Germany, Schumacher's accident topped news bulletins, with the bestselling tabloid newspaper Bild reporting on its website: "Schumi fighting for his life".
Schumacher is under the care of Professor Gerard Saillant, a brain and spinal injury expert who is also president of the International Automobile Federation (FIA) Institute. Saillant told the news conference he was there as "a friend" and gave no further details on his condition.
Bild reporters said Ross Brawn, the Briton who worked with Schumacher at Ferrari and Mercedes as technical director and team principal respectively, had arrived in Grenoble.
Leading names in motor racing reacted with shock on Twitter.
"If anyone can pull through, it's him," said Britain's triple Indy 500 winner Dario Franchitti, who is still walking on crutches after a crash in October that ended his racing career.
"Come on Michael, give us one of those race stints at pure qualifying pace to win through, like you used to. You can do it," said Schumacher's former Benetton team mate Martin Brundle.
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Former Ferrari team mate Felipe Massa, who suffered a near fatal head injury at the 2009 Hungarian Grand Prix, said he was praying for his friend.
Red Bull's quadruple world champion Sebastian Vettel, Schumacher's friend and compatriot, expressed his shock and support for the family.
Schumacher is the most successful Formula One driver of all time with a record 91 race victories in a career spanning more than two decades.
He won his first two titles with Benetton in 1994, the year when Brazilian triple champion Ayrton Senna died in a crash at the San Marino Grand Prix, and 1995.
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The German then took five in a row with Ferrari between 2000 and 2004 in what now seems a golden age for the Italian team who named a square after him outside Enzo Ferrari's old house at their Fiorano test track.
Schumacher left the sport last year after a less successful three-year comeback with Mercedes following an earlier retirement from Ferrari at the end of 2006. He lives in Switzerland with his wife and two children.