Celine Dion no longer has "control over her muscles," according to an update shared by her older sister Claudette.
Last December, the 55-year-old 'My Heart Will Go On' hitmaker announced on social media that she was canceling her upcoming tour dates after being diagnosed with stiff person syndrome.
Celine posted a video, talking about prioritizing her health during this difficult time, saying: "Hello everyone, I'm sorry it's taken me so long to reach out to you. I miss you all so much and can’t wait to be on stage talking to you in person.
"I’ve been dealing with problems with my health for a long time and it has been really difficult for me to face my challenges and to talk about everything that I’ve been going through, " she continued.
Watch Dion reveal her heartbreaking diagnosis below:"Recently I’ve been diagnosed with a very rare neurological disorder called the stiff person syndrome which affects one in a million people," she told her followers.
When discussing how the disease has impacted aspects of her life, the star said: "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."
Stiff person syndrome - also known as SPS or stiff-man syndrome - is a rare and incurable neurological disease that causes progressive muscle stiffness and painful spasms.
It affects the central nervous system, including the brain and spinal cord, and rigidity can fluctuate, mainly affecting the torso, arms, and legs.
It is more commonly seen in women than men and can be exacerbated by noise, touch, and emotional distress, according to the National Institute of Neurological Disorders and Stroke.
The 'All By Myself' musician's older sibling has now given an update to fans on how Celine is doing with the neurological disorder.
Speaking to Canada’s 7 Jours (via the Daily Mail), Claudette revealed that her sister is "working hard" but has lost the ability to "control her muscles," adding: "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.'"
Back in May, the Canadian musician was forced to pull the remaining dates of her Courage world tour, and explained on Instagram that she was "working really hard to build back my strength".
"I’m so sorry to disappoint all of you once again...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," she added.
However, in the new interview, Claudette played down the possibility of her returning to full-scale touring, stating: "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."
The 'Power Of Love' vocalist's sister told the publication that the rarity of the condition - which is thought to affect just one in a million people - means progress has been slow.
"The vocal cords are muscles, and the heart is also a muscle. This is what comes to get me. Because it’s one out of a million cases, the scientists haven’t done that much research because it didn’t affect that many people," Claudette shared.
She added that Celine and her family remain hopeful as the musician's family charity, Fondation Maman Dion, has been inundated with messages of support for the star.
"Some people have lost hope because it’s an illness that isn’t well known. If only you knew the number of phone calls the Foundation gets about Celine!", Claudette said. "People tell us they love her and they’re praying for her. She gets so many messages, presents, and blessed crucifixes."