GRENOBLE, France -- Michael Schumacher underwent a second surgery after a brain scan showed small, "surprising" signs of improvement, but grim doctors said Tuesday they could offer no insight into the prognosis for the retired Formula 1 champion.
Schumacher, who turns 45 on Friday, suffered critical head injuries when he fell and struck a rock Sunday while skiing on a family vacation in the French Alps. His manager confirmed that the accident cracked his helmet. Doctors credited the helmet with giving him a chance at survival.
Schumacher's condition stabilized somewhat after the second surgery, but he remains in a medically induced coma - and doctors gave no prediction on how long that would last.
"We cannot tell you any more about the future," said Gerard Saillant, a surgeon and friend of the family who is in Grenoble. Saillant said it would be "stupid" to make any predictions about Schumacher's recovery.
Schumacher and his 14-year-old son were skiing in the French Alpine resort of Meribel, where the family has a chalet, when he fell and hit the right side of his head on a rock. He was taken first to a local hospital, then to Grenoble University Hospital, which is recognized as having one of France's best neurology teams.
Dr. Emmanuel Gay, the hospital's chief neurosurgeon, said a brain scan performed late Monday showed bruising "a little bit everywhere" in Schumacher's brain - but also an unexpected easing of pressure.
"The brain scan was, I must say, surprising," he said.
But he and other doctors cautioned that Schumacher's condition was still grave after the successful surgery to eliminate the largest and most accessible bruise, on the left side of his brain.
"We cannot say he is out of danger," said Dr. Jean-Francois Payen, head of the hospital's intensive care unit. Payen said any neurological evaluation was "out of the question" for now.
Schumacher earned universal acclaim for his uncommon and sometimes ruthless driving talent, which led to a record 91 race wins. He retired from Formula 1 last year after garnering an unmatched seven world titles.
Schumi, as his fans affectionately call him, was famously aggressive on the track and no less intense off-hours. In retirement, he remained an avid skier, skydiver and horseback rider.
Schumacher's manager, Sabine Kehm, offered more details on the accident, confirming that his helmet cracked on impact.
"It looks like probably that initiating a corner, he was hitting a stone which he had not seen and was catapulted down on a rock," Kehm said in English. "That is extremely and very unfortunate ... really very, very bad luck. Michael was not at high speed."