Celine Dion has been "unable to find any medicine" to successfully treat her stiff person syndrome.
The 'My Heart Will Go On' singer revealed last December she had been diagnosed with the condition - a rare neurological disease which can cause rigid muscles, spasms and frequent falls - and her sister Claudette has given a new update on her health and explained their other sibling, Linda, has moved into the 55-year-old megastar's house to help care for her.
According to Shemazing.net, Claudette told Le Journal de Montreal: "When I call her and she's busy, I speak to my sister Linda who lives with her and tells me that she's working hard. She's listening to the top researchers in the field of this rare disease as much as possible...
"We can't find any medicine that works, but having hope is important."
Claudette believes the most important thing Dion can do is to rest and she had no choice but to cancel her world tour earlier this year.
She said: "I honestly think that she mostly needs to rest. She always goes above and beyond, she always tries to be the best and top of her game. At one point, your heart and your body are trying to tell you something. It's important to listen to it."
The 'Think Twice' hitmaker's family "trust" her to find a rehabilitation plan that works for her.
She added: "It's innate to her, she's disciplined in every area of her life."
In May, Dion confirmed she was cancelling all her remaining scheduled live performances.
A statement on her website read: "As the world has emerged from the pandemic, Celine has continued to be treated for a diagnosed medical condition that prevents her from performing. Celine is working hard on her recovery.
"We do have every hope that someday soon, Celine will be able to come to all of these cities in Europe to perform for her amazing fans, but that time is simply not now.
"Celine's medical team continues to evaluate and treat the condition."
She also addressed the cancellations on Twitter and insisted she wouldn't give up on her touring ambitions.
She wrote on the micro-blogging platform: "I'm so sorry to disappoint all of you once again... and even though it breaks my heart, it's best that we cancel everything until I’m really ready to be back on stage... I'm not giving up… and I can't wait to see you again! – Celine xx (sic)"