It may take Michael Schumacher any time between one and three years to recover, a French doctor who treated him after his skiing accident has revealed.
Jean-Francois Payen, who cared for Michael while he was in hospital in Grenoble, added that the Formula 1 champion was making "some progress" but that it would take time.
The doctor was speaking to French radio station RTL and Le Parisien newspaper when he gave updates about Michael's health on Thursday.
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Michael Schumacher is being treated at home in Switzerland
"It's like for other patients, we are on a timescale which goes from one year to three years and we need to be patient," said Dr Jean-Francois.
Michael, 45, is being cared for in his family home in Lausanne, Switzerland with a team of 15 carers, according to reports. It is understood that he is immobile and unable to speak.
Dr Jean-Francois has been visiting the driver to check up on his progress and tell Michael's wife Corinna and the family about any changes.
Praising the athlete's wife for her "extraordinary willpower," Dr Jean-Francois added: "Immediately she understood the seriousness of the situation and the long journey that lay before them. She sees things very clearly and will do anything and give everything to improve the condition of her husband."
Michael Schumacher's doctor Jean-Francois Payen treated him in December 2013
Michael suffered his skiing accident shortly before New Year's Eve last year when he was in the French Alps on holiday. The world champion from Germany fell and hit his head on a rock, leaving him with severe head injuries.
Michael was immediately treated in Grenoble and placed in a medically induced coma, and was later moved to a facility in Lausanne, Switzerland. Just last month he was moved to continue his rehabilitation process at home.
"Considering the severe injuries he suffered, progress has been made in the past weeks and months," his manager Sabine Kehm said in a statement. "There is still, however, a long and difficult road ahead."
The motor legend retired from F1 for a second time in 2012 having won seven world championships and secured 91 race victories during his 19-year career.