Celine Dion, 55, has lost the ability to control her muscles as she continues to battle stiff-person syndrome, a rare neurological disorder.

One year after sharing she was diagnosed with stiff-person syndrome, the singer can no longer control certain body movements, according to her sister Claudette Dion.

"She doesn't have control over her muscles," Claudette told 7 Jours, via translation from French. "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," she said.

She also noted, "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."

In May, Celine canceled her Courage World Tour due to the rare neurological disorder, which can cause painful muscle spasms and stiffness.

"I'm so sorry to disappoint all of you once again," the 55-year-old wrote on Instagram at the time. "I'm working really hard to build back my strength, but touring can be very difficult even when you're 100%. It's not fair to you to keep postponing the shows, and even though it breaks my heart, it's best that we cancel everything now until I'm really ready to be back on stage again."

According to Claudette, their sister Linda has been living with Celine in the Las Vegas area as she receives care from doctors who specialize in stiff-person syndrome.

And although the Grammy winner focuses on resting, she was recently able to spend quality time with her 22-year-old son René-Charles and 13-year-old twins Nelson and Eddy, who she shared late husband René Angélil. Celine and her sons headed to the hockey arena Oct. 30, stepping out to watch the Montreal Canadiens take on the Vegas Golden Knights.

In footage posted online, Celine was seen meeting with coach Martin St. Louis and posing for a group photo.

"It's such an honor to meet you," she told him, via translation from French. "It was an incredible night."