Céline Dion’s battle with a condition known as Stiff Person Syndrome continues, according to the singer’s sister, who said that the Canadian songstress “no longer has control of her muscles.”

Claudette Dion spoke with French language Canadian outlet 7 Jours, according to the Daily Mail, and said that her younger sister, 55, still wanted to return to the stage, but that the progressive disease continues to take its toll.

“She’s working hard, but she doesn’t have control over her muscles,” Claudette said. “What breaks my heart is that she’s always been disciplined. She’s always worked hard. Our mother always told her, ‘You’re going to do it well, you’re going to do it properly.’ It’s true that in both our dreams and hers, the goal is to return to the stage. In what capacity? I don’t know.”

She elaborated on the impact the illness has on her sister’s life, and how much is unknown about the condition.

“The vocal cords are muscles, and the heart is also a muscle,” she said. “This is what comes to get me. Because it’s one out of a million case, the scientists haven’t done that much research because it didn’t affect that many people.”

In an emotional January 2022 statement, the Grammy Award winner announced that she would postpone planned tour dates amidst health struggles, sharing publicly for the first time that she suffered from the severe muscle spasms as a result of a rare neurological disease. The debilitating spasms can be so strong and violent that they can break bones.

When postponing the world tour dates in 2022, Dion said she was frustrated with the illness.

“It’s taking a lot longer for me to recover than I’d hoped,” she wrote.

In late October, the singer made her first public appearance in more than three years, accompanying her three sons to a hockey game in Las Vegas, as well as the final show of Katy Perry’s Vegas residency.

Claudette said that her sister is working with top researchers for treatment, and thanked fans for their outpouring of support.

“If only you knew the number of messages the foundation gets about Celine! People tell us they love her and they’re praying for her,” she said. “She gets so many messages, presents, and blessed crucifixes.”