Michael Schumacher's agent has said there are small signs that the Formula One champion will wake from the coma he has been in for more than two months.

But the statement from Sabine Kehm tempered optimism with caution.

"We are and remain confident that Michael will pull through and will wake up.

"There sometimes are small, encouraging signs, but we also know that this is the time to be very patient," Ms Kehm said.

Schumacher was taken to hospital after a ski crash in the French ski resort of Meribel in December. He suffered severe head injuries when he fell and hit the right side of his head on a rock off the side of a demarcated slope.

His family has released few details about his condition.

Doctors operated to remove blood clots from his brain, but some were too deeply embedded.

Neurologists not involved in his treatment say full recovery appears increasingly unlikely, given the coma's duration and the extent of his injuries.