Science
Stiff person syndrome is a neurological and autoimmune disorder that can cause excruciating muscle spasms and rigidity. We still don’t know exactly what causes it.
ByChristina Sterbenz
Published October 3, 2023
• 9 min read
Even though it can cause excruciating and debilitating muscle spasms, most people had never heard of stiff person syndrome until late last year, when singer Celine Dion announced her diagnosis. This rare neurological and autoimmune disorder is thought to affect just one or two people in a million—two-thirds of them women.
“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,” Dion explained on Instagram as she canceled several of her 2023 shows.
Dion’s announcement brought the disease into the spotlight. In addition to muscle spasms, people can experience rigidity and decreased mobility, and in rare cases, cognitive function can be impacted. And the disorder is progressive, meaning it can get worse over time.
While stiff person syndrome takes an average of seven years and many visits to specialists to diagnose, doctors hope Dion’s transparency will increase awareness and spur more funding to research that could finally help others solve the mystery of their pain.
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“It’s this sort of diagnostic odyssey, as I like to refer to it,” says Scott Newsome, director of the Johns Hopkins Stiff Person Syndrome Center and a professor of neurology. “[Patients] keep bouncing around until they land in the hands of a clinician that may be familiar with the condition.”
What causes stiff person syndrome?
It’s still not clear exactly what causes stiff person syndrome, Newsome says. It hasn’t been as researched as other autoimmune conditions, like multiple sclerosis which can also cause muscle spasms and stiffness. But scientists do know it’s tied to a malfunction of the immune system.
For most healthy people, a neurotransmitter called GABA helps control their body’s muscle movement. But for people with SPS, their immune systems produce antibodies that block the pathways GABA travels along, causing muscle spasms.
Think of the connections between muscles and nerves as a lock, and antibodies as a key, says Jim Weiss, a retired nephrologist and board member for the Stiff Person Syndrome Research Foundation.
“The abnormal antibody goes where it shouldn’t be,” he says. What those antibodies are mostly blocking, or locking up, are the pathways that prevent your muscles from contracting. “So if you block inhibition of muscle contraction, then you get excessive muscle contraction.”
Weiss’ son Michael was diagnosed as a teenager with stiff person syndrome. Both he and his wife, also a doctor, were generally aware of the condition but their son’s diagnosis still came as a surprise. Ultimately, it took about two years and countless doctors and misdiagnoses for Michael and his family to finally find an answer.
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But Michael, now 21 and a senior at Michigan State University, considers himself fortunate to have parents with enough expertise to advocate for him since the average time for an SPS diagnosis is seven years.
“There are lots of stories, particularly of women, who have had a very hard time getting anybody to take their stories to be credible,” Jim Weiss says.
Symptoms of stiff person syndrome
Part of what makes SPS so difficult to diagnose is the variety of symptoms and where they might appear in the body.
Most commonly, people experience spasms and rigidity in their back, shoulders, and neck—and for some it’s so intense that they’re confined to their beds or the ICU for extended periods of time.
“When I was first getting sick and diagnosed, it was very debilitating,” Michael says. “I wasn’t able to walk. I wasn’t able to sleep. I just was bed-bound and completely non-functioning.”
Jim Weiss says he could even see the muscles constricting in his son’s back.
“His muscles along his spine were like a rope you could see from 10 or 15 feet away. Like you might see a charley horse in somebody’s calf, that’s what his muscles looked like,” Jim Weiss says.
Pain comes from more than the spasms themselves. Those with SPS often experience lingering soreness, and end up favoring different muscles or changing their gait to cope with the pain. That can also cause other imbalances and issues, Newsome says.
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And that’s not to mention what he calls the “invisible pain,” like fatigue and anxiety.
“I have yet to meet an individual with this condition who hasn’t had anxiety,” Newsome says. That’s not just due to the emotional impact of the condition; it’s biological: GABA is known for having a calming effect on the body—and inhibiting it can cause anxiety.
Symptoms can also manifest themselves internally. Some people may develop slurred speech or difficulty speaking (Dion noted an impact on her singing), while others experience abnormal contractions of their gut muscles, which can cause bloating, cramping, and diarrhea.
Even though scientists don’t yet know the cause of stiff person syndrome, they do know that being startled or going through emotional distress can trigger its symptoms. Claire Riley, a professor of neurology at Columbia University Irving Medical Center in New York City, remembers a patient who was going through a divorce and would often have disruptive spasms when she would appear in court.
How do doctors diagnose stiff person syndrome then?
Before Michael and his family learned he had stiff person, he was misdiagnosed with a variety of other disorders, including amplified pain syndrome, dystonia, functional neurologic disorder, and psychosomatic disorder.
“And many diagnoses of ‘I don’t know,’” says Jim Weiss, who also notes people are often misdiagnosed with multiple sclerosis and Parkinson’s disease as well.
Another reason that SPS is difficult to diagnose is simply a lack of knowledge: Some doctors, and many patients, have never heard of the condition, making self-advocacy difficult.
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Some clues, however, do exist. A latent onset in adulthood of type 1 diabetes, which typically occurs in children or young adults, can occur alongside stiff person syndrome because instead of just impacting the neurotransmitter, cells in the pancreas are actually destroyed, according to Riley. Diverse types of cancers can also accompany SPS because the same antibodies that the immune system releases to kill cancer cells can also block muscle inhibition.
One hallmark sign, especially as the condition progresses, is called hyperlordosis, an excessive curve in the lower spine also known as “hollowback” or “swayback,” according to Newsome. Other signs can include tightness in the muscles surrounding the spine and rigidity in the limbs.
A blood test can also help determine if someone has high levels of the GAD65 antibody (glutamic acid decarboxylase 65-kilodalton isoform), which can be a biomarker of autoimmune disease. But about 1 in 100 people test positive, and only about 1 in 10,000 who test positive end up having SPS. Some people with GAD are also perfectly healthy.
“It’s worth saying that this is not a good screening test in someone without typical symptoms,” Riley says.
So what can you do about it?
Treatment can also be very individualized.
Riley says she tries to approach treatments in two ways: first addressing the symptoms and then using immunotherapy to slow the progression of the condition.
Treating symptoms might involve physical therapy to help people cope with muscle-related issues. Some patients also require medication, such as immunosuppressants like steroids, although these are often given in low doses and short courses because they can put patients at risk of developing other infections. Newsome says benzodiazepines, like clonazepam, which effectively increase GABA levels, can be helpful for muscle spasms as well as anxiety. Other muscle relaxants, anticonvulsants, and pain relievers may also be prescribed.
When traditional treatments don’t work, plasmapheresis, which removes or exchanges blood plasma from the body, can also be an option. As a form of immunotherapy, the procedure can remove pathogenic antibodies from the body.
“It’s similar to dialysis,” says Michael, who underwent the procedure. “I was inpatient for a long treatment, which was a few hours every other day for, I think, the course of two weeks. …It wasn’t painful, but it was not fun.” Although Michael went into remission after that treatment, some of his symptoms have since returned.
Sometimes, however, management is really all patients can hope for—at least until more research is done. And more research means more money.
“The support and the funding behind rare diseases is not as robust as more common conditions, for example, multiple sclerosis,” Newsome says. “And I personally feel it’s a disservice to those that have a rare condition—and everyone that’s connected to that person — because …. this totally turns the patient’s world upside down.”
Jim Weiss noted that the Stiff Person Syndrome Research Foundation received a few more donations in the months after Dion’s diagnosis but nothing notable or sustained. The biggest positive, for him, was the awareness her announcement brought to the public.
“Celine’s announcement also took real courage and personal strength,” he says. “This has been helpful to many individuals with SPS, lending credibility and support to people who are so often misdiagnosed and viewed with skepticism.”
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