The father-of-two, who has been in an induced coma for four weeks following a skiing accident in France, may "never make a full recovery," according to new reports.
Michael's family have insisted that "he is a fighter" and wrote an emotional note on the former F1 world champion's official website.
"We are deeply touched by all the messages to get well soon for Michael, which still are being sent," said the statement. "That gives us strength. Thank you all so much! Thank you to the Fanclub in Kerpen, to 1. FC Köln and Schalke 04 but also to everybody else and other fan groups who are supporting Michael. We all know he is a fighter and will not give up!"
Recent reports have speculated that Michael has had permanent brain damage and may be suffering from apallic syndrome, or persistent vegetative state. This would mean Michael would live in a state of partial arousal rather than complete awareness.
Michael was put in a medically-induced coma just before New Year to relieve pressure on his brain, and most patients are usually kept in such comas for a maximum of two weeks. If doctors did manage to bring him out of the coma, Michael would still be unable to speak, move or feed himself.
"More than three weeks after the tragic skiing accident of the seven-time Formula 1 world champion Michael Schumacher, fears grow that he will never make a full recovery," reported Austrian news website format.at.
"Every day, every week in a coma the chances decline that the situation is improving," added Jean-Marc Orgogozo, professor of neurology at the University of Bordeaux.
Michael, who is married to German-born Corinna and is father to Gina Maria and Mick, was with his teenage son at the time of the accident. The seven-time F1 champion was taken to hospital after he hit his head on a rock while skiing off-piste in Meribel.