Celine Dion's rare condition: Stiff-person syndrome explained

She made the announcement in emotional, five-minute message posted in French and English on Thursday and revealed it had left her with spasms affecting her ability to walk and sing.

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

"I miss seeing all of you, being on the stage, performing for you. I always give 100 per cent when I do my shows but my condition is not allowing me to give you that right now."

Stiff-person syndrome (SPS) is a rare, chronic autoimmune and neurological disorder that causes rigidity and spasms in the trunk and limbs.

It can affect posture, balance and the ability to use certain muscles.

The main symptoms are muscle stiffening in the torso and limbs, and episodes of violent muscle spasms. These can be triggered by environmental stimuli (such as loud noises) or emotional stress.

Muscle spasms can be so severe they cause the person to fall down. People can have difficulty walking and, over time, even greater disability.

In some cases, SPS can be progressive and painful.

Most people start experiencing symptoms between the ages of 30 and 60.

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SPS is thought to be an autoimmune disorder, where the immune system is overstimulated and antibodies are generated which attack neurons that inhibit activity in the brain.

There is no cure for SPS, but symptoms can be managed.

Doctors can use sedatives, muscle relaxants and steroids to help restore balance as well as target the immune system to stop it from attacking the nervous system.

Medications and immunotherapy may be prescribed, with aqua, occupational and physical therapy

SPS can potentially progress to cause significant disability or life-threatening complications such as respiratory compromise.