Celine Dion's health update amid Stiff-Person Syndrome battle

Celine Dion's sister has revealed the 55-year-old has lost control of her muscles amid her battle with a rare neurological disorder.

Claudette Dion told Canadian magazine 7 Jours her younger sister's health battle pained her.

"There are some who have lost hope because it is an illness that is not known," she said.

"She works hard, but she doesn't have control of her muscles.

"The vocal cords are muscles, and the heart is also a muscle."

She said her sister still dreamed of returning to the stage.

"In which state? I do not know," she said.

"Since it's one in millions, scientists didn't do that much research, because it didn't affect that many people."

But Ms Dion said the family had been inundated with support.

"People tell us they love her and pray for her. She receives so many messages, gifts, blessed crucifixes," she said.

Rare disorder affects 'every aspect of daily life'

"Unfortunately these spasms affect every aspect of my daily life, sometimes causing difficulties when I walk, and not allowing me to use my vocal chords to sing the way I'm used to," she said.

"I have to admit it's been a struggle. All I know is singing is what I've done all my life and it's what I love to do the most."

There is no cure for Stiff-Person Syndrome (SPS), which causes rigidity and spasms and affects posture, balance and the use of some muscles but treatments can help manage symptoms.