The seven-times F1 champion Schumacher suffered grave head injuries when he fell on a rock in a skiing accident in France on December 29, 2013.
He spent months in an induced coma, was moved from hospital to a rehabilitation clinic in June 2014, with his rehabilitation continuing at home in Switzerland in September that year.
Only the family and the closest friends know how Schumacher is doing shortly ahead of his 47th birthday on January 3.
Last week Kehm denied a magazine report that Schumacher could walk again, saying speculation of this nature was "irresponsible" because "for Michael in view of the severity of his injuries the protection of his privacy is very important".
It also raised "false hopes" for fans and well-wishers, she added.
Kehm has always been reluctant to raise any kind of hopes, speaking of progress here and there but always highlighting the grave nature of the injuries which even a helmet Schumacher wore on that fateful day could not prevent.
Damm said questions will always remain because "you won't be able to say I will make a statement and clear up all open questions".
"Instead, every statement would lead to new questions."
While Schumacher recovers his children are entering the spotlight. His daughter Gina is a successful western horse-rider like his wife Corinna. Their 16-year-old son Mick Schumacher had his debut in motor racing this year.
His first Formula Four practice sessions on the German track in Oschersleben generated huge media attention and he is expected to continue in the same series in 2016.
-AAP
