It is understood that the three-time Formula 1 world champion was admitted to the Paris clinic under a false name. His medical treatment involved experimental stem cell surgery, says local newspaper Le Parisien. A hospital employee said, "Yes, he is at my service.
"And I can guarantee he's aware."
Professor surgeon Philippe Menasche welcomed Schumacher, 50, at the hospital last Monday.
The 69-year-old is known for performing the world's first embryonic cell transplant in a heart failure patient.
Schumacher reportedly visited the hospital twice before by helicopter.
The health of the German legend has been a closely guarded secret since he suffered catastrophic brain injury in a ski accident in 2013.
Schumacher's career led him to a record of seven world titles and the highest number of wins (91) for a rider ever.
But after the accident, the German driver was in a coma induced for almost six months.
In June 2014, he was discharged from the hospital and has since received medical attention at home near Lake Geneva in Switzerland.
She said, “Michael has always been a very warm person.
“But he didn't want this side of him to be public, because he wanted to look like he was focused on competition.
Kehm has always insisted that the condition of the superstar is not a public matter.
Kehm shared details about Schumacher's thoughtful side, which were highlighted at his employees' birthdays and during the Christmas holidays.
She said, “He always wanted to give them original gifts.
"He knew he was very picky.
"So he definitely wanted to give something back to them."
Additional reporting by Monika Pallenberg