By Lindsey Bever, Richard Sima and Annabelle Timsit
Celine Dion announced that she was diagnosed with a rare and incurable neurological condition known as stiff-person syndrome and that she will cancel or postpone dozens of shows in her "Courage World Tour."
In an emotional, five-minute Instagram video posted on Thursday, Dion, 54, told fans: "I've been dealing with problems with my health for a long time, and it's been really difficult for me to face these challenges and to talk about everything that I've been going through."
What is stiff-person syndrome? We spoke with neurologists and a pain specialist to answer common questions about the unusual disorder, including how it's diagnosed and whether it affects longevity.
What is stiff-person syndrome?
Stiff-person syndrome (SPS) is a rare, chronic neurological disorder that causes muscle stiffness and sometimes intense muscle spasms in the trunk and limbs, affecting posture, balance and the ability to use certain muscles. It usually has an autoimmune component, and in some cases, it can be progressive and painful, experts say.
Andrew McKeon, professor of neurology at the Mayo Clinic, said SPS affects nerves in the spinal cord and neurons in the brain that regulate movement. In other words, when the nervous system becomes overly excited, it can send too many signals to the muscles, causing them to stiffen or spasm.
A person's "whole body can seize up when startled or in other situations," putting them at risk for falls and injuries, he said.
The syndrome affects women at twice the rate of men, experts say, and although it can affect a person at any age, it is most often diagnosed among middle-aged people.
What are the symptoms? Is it painful?
SPS causes muscle stiffness, muscle aches and muscle spasms, often in the lower back and legs, which can make it difficult for some patients to walk. Those who have symptoms that are not well-controlled may need to use a walker or wheelchair to keep from falling or injuring themselves.
The muscle spasms are what neurologists call "stimulus sensitive" and can be provoked by a sudden noise, light touch or even emotional distress. One form of the condition can affect muscles that control the eyes, speech or singing or swallowing.
"Just imagine having the worst Charley Horse you can have, but it's affecting a ton of muscles in your lower back and legs - and it's constant. It's very painful," said Kunal Desai, assistant professor of neurology at Yale University.
Chi-Ying "Roy" Lin, a neurology professor specialising in movement disorders at Baylor College of Medicine, said in the cases he has seen, patients "were very, extremely uncomfortable, and it's usually very painful."
"And when the pain occurs, it's very debilitating, no matter what position, he added. "There's basically no comfortable position for them to stay, either sitting or laying."
The condition typically only affects skeletal muscles that we can voluntarily control. It does not seem to affect cognition but may be associated with anxiety.
In her statement, Dion said the spasms have made her life difficult.
"Unfortunately, these 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.
Because of her diagnosis, the singer said she "won't be ready to restart my tour in Europe in February."
What is the life expectancy for someone with stiff-person syndrome?
Although SPS is rare and not completely understood, experts say the syndrome does not typically have an effect on longevity, except in very rare circumstances in which muscles used for breathing or swallowing are compromised.
When symptoms are well-controlled, patients can live a relatively normal life. However, when the symptoms are not able to be managed, they can suffer significant impairments, experts say.
Lin said the main effect is on quality of life. "I don't think for the cases I saw, their life quality ever comes back to like normal baseline," Lin said.
What causes it? What are the risk factors?
SPS is thought to be an autoimmune disorder where the immune system is overstimulated and generates antibodies that target neurons that inhibit activity in the brain. There is no clear mechanism for why these antibodies are generated, Lin said.
Most SPS patients have antibodies to glutamic acid decarboxylase or GAD65, an enzyme that produces the important inhibitory brain chemical GABA. The immune response against GAD65 may reduce the amount of GABA that normally inhibits neuronal activity, heightening neuronal signals sent to muscles, which can cause spasms.
Although it was originally called stiff-man syndrome when it was first described in 1956, the majority of diagnosed patients tend to be middle-aged Caucasian women though it can occur in patients of different ages and backgrounds.
Although it's a rare disease, when it is diagnosed, it's common to see it alongside other conditions, including diabetes, thyroid disorders and pernicious anaemia.
"The world will benefit from having more understanding about this disease because it's just so rare," Lin said.
How is stiff-person syndrome diagnosed?
SPS is diagnosed based on symptoms, through neurological and neuromuscular exams, including using electromyography, or EMG, to test muscle and nerve function. Diagnosis also often relies on a blood test that measures the GAD antibody.
Because the symptoms can share similarities with multiple sclerosis and various muscular dystrophies, it "can be a challenging diagnosis to make, and it does require some expertise," McKeon said.
Lin notes that it is very common to have some muscle spasms in normal, everyday life and that very small amounts of antibodies against GAD65 is not abnormal. For diagnosis of stiff-person syndrome, the antibody amount against GAD65 must be very high.
How is it treated?
SPS is not curable, but it can be managed, experts say.
Treatment is aimed at targeting the nervous system directly to restore balance, as well as targeting the immune system to stop it from attacking the nervous system, McKeon said.
For patients who have an autoimmune cause, treatment may include intravenous immune globulin (IVIG), a treatment that uses antibodies to blunt the immune response. Other treatments involve using muscle relaxants, anti-convulsants and pain medications for those experiencing pain.
In addition, Pavan Tankha, medical director of Comprehensive Pain Recovery at the Cleveland Clinic, said he refers patients to pain psychologists, physical therapists and other health professionals "to try to improve their overall quality of life and decrease the suffering associated with pain."
"Pain simply isn't what you feel; it's also what it does to you," he said.
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