The hopeful letter Michael Schumacher’s wife wrote about her husband's condition.

Michael Schumacher’s family have barely spoken about his condition publicly since he suffered brain damage in a devastating skiing accident in 2013.

But a recently surfaced note Corinna Schumacher, 49, wrote about her husband has given a rare insight into the Formula One champion’s condition.

On 29 December 2013, the race car driver was downhill skiing on holiday in the French Alps when he lost control and crashed. The now-49-year-old was placed in an induced coma because of his traumatic head injuries and remained unconscious for months.

It’s believed that since September 2014 the German has been cared for by medical experts at his home near Lake Geneva in Switzerland – but the most concrete update on his condition since has simply been that he “cannot walk” as of September 2016.

This month German musician Sascha Herchenbach gave an interview to German magazine Bunte in which he shared the thank you note Corinna wrote him after he wrote a song about the retired F1 driver. The song, Born To Fight, was released in 2014, but the date the note was sent is unknown.

michael schumacher wife corinna
The couple at a party during the F1 Grand Prix in Monaco in 2011. Image Getty.

"I would like to sincerely thank you for your message and nice gift that will help us through this difficult time," her message, translated from German, read.

"It is good to receive so many kind wishes and other well-intentioned words - which is a great support for our family.

"We all know Michael is a fighter and will not give up."

Sascha told the magazine he hadn't expected to receive a reply when he sent the Schumachers a recording of the song.

"I had not expected to get an answer and was overwhelmed.

"The letter was handwritten and signed by Corinna on her stationery. She wrote that she was very thankful for the gift and helped her and her family over this difficult time."

Fans still holding out hope of the racing legend making a recovery were encouraged by a message his daughter Gina-Maria posted to Instagram last November.

"There is only one happiness in this life, to love and be loved #keepfighting," she wrote.

Most of the updates on Schumacher's condition have come via unconfirmed reports, including one in 2015 that he had suffered memory loss, could not speak, but reacted to his family's voices.

According to French magazine Paris Match, despite still being unable to speak, the seven-time world champion was showing even more emotion.

"When you put him in his wheelchair facing the beautiful panorama of the mountains overlooking the lake, Michael sometimes cries," an anonymous relative reportedly told Paris Match in August this year.