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What Is Stiff Person Syndrome?

Stiff person syndrome (SPS) has been in the news recently due to Celine Dion sharing her diagnosis, but what exactly is this rare neurologic disorder? 


It’s not often that a rare neurologic disorder makes headlines, but you may have seen stiff person syndrome (SPS) in the news lately. Internationally acclaimed singer Celine Dion recently revealed that she had been diagnosed with the condition, causing her to cancel an upcoming 2023 tour. Her heartfelt announcement about her diagnosis moved her fans and made many people curious to know what SPS is and how it’s treated.

Often misdiagnosed for other more common conditions, stiff person syndrome affects approximately one in a million people. About twice as many women as men suffer from SPS.

Researchers are still working to understand why that is and discover the underlying causes of this disease. Though it is uncommon, learning more about this rare neurologic disorder may help shed light on other related diseases.

What Is Stiff Person Syndrome?

Stiff person syndrome is a neurologic disorder characterized by muscle spasms and progressive muscle stiffness. Muscle stiffness tends to fluctuate, often occurring along with muscle spasms. Spasms can happen randomly or be triggered by sudden noises, physical contact, and even emotional distress. Because people with SPS may have limited range of movement and impaired reflexes, intense spasms can sometimes cause falls and injuries.

Most people start experiencing SPS symptoms between the ages of 30 and 60. The severity of symptoms can range from person to person, and people with more acute symptoms may develop a hunched posture or require the use of a wheelchair. People with SPS are also more likely to suffer from anxiety and depression.

What Causes SPS?

Researchers are still trying to find out what causes stiff person syndrome. However, they suspect it may be due to an autoimmune reaction in which the immune system attacks a protein called GAD (glutamic acid decarboxylase). 

Antibodies are proteins that latch onto unwanted substances in the body (such as bacteria and viruses) in order to eliminate them from your system. This is your immune system’s way of protecting your body and fighting illness and infection. When someone has an autoimmune disease, their antibodies mistakenly attack normal, healthy cells. Researchers have found that people with SPS often have high levels of anti-GAD antibodies and are currently trying to understand if this type of autoimmune reaction plays a role in the formation of the disease.

GAD helps make an important substance called GABA (gamma-aminobutyric acid), which regulates motor neurons by decreasing their activity. Fewer normally functioning GAD proteins leads to low GABA levels. That, in turn, can cause motor neurons that GABA regulates to fire continuously, making it difficult for the body and mind to relax. Low GABA levels are also linked to increased anxiety and depression, which affect many people with SPS.

How Is Stiff Person Syndrome Diagnosed?

Due to its rarity and symptoms that overlap with other common conditions, SPS is often misdiagnosed as multiple sclerosis, Parkinson’s disease, and fibromyalgia. Typically blood testing plays a key role in getting a correct diagnosis. Antibody tests can detect the extremely elevated levels of GAD antibodies present in the blood and spinal fluid of most people with SPS. 

In addition to antibody tests, doctors can also use electromyography (EMG) to aid in diagnosis. An EMG test allows doctors to examine and record the electrical activity of various muscles throughout the body. This can help confirm an SPS diagnosis as well as monitor one’s response to medication and other treatments.

Is Stiff Person Syndrome Permanent?

Stiff person syndrome is a chronic condition, and there is currently no cure. Because each person’s symptoms can vary from mild to severe, treatment requires a personalized approach. Generally, doctors focus on mitigating pain, relaxing muscles, and suppressing a person’s overactive autoimmune response. 

Medications used may include sedatives, muscle relaxers, anti-anxiety drugs, and steroids. Botox is sometimes used to reduce muscle spasms when medications are not effective at controlling symptoms. To address the autoimmune response that is suspected to cause SPS, doctors may also utilize intravenous infusions—filtering the blood to remove GAD antibodies—and other immunotherapies like stem cell treatment.

Research Is Key to Curing Rare Neurologic Diseases Like SPS

More research is needed to understand precisely what causes stiff person syndrome, what the most effective treatments are, and ultimately, how to cure this rare neurologic disease. Researchers have noted that many people with SPS also have another autoimmune disease, such as type 1 diabetes, pernicious anemia, thyroiditis, or vitiligo. Additionally, SPS seems to be more common in people with certain types of cancer, including lymphomas, breast cancer, lung cancer, thyroid cancer, colon cancer, and kidney cancer.

The American Brain Foundation is currently funding a research project led by Alexander Gill, MD, PhD, which is investigating the connection between neuroinflammation and the loss of NLRX1—a protein that plays a role in the immune system—in multiple sclerosis (MS). While the goal of this research is to identify potential treatments for MS, projects like Dr. Gill’s also help us better understand related diseases and reduce the likelihood of misdiagnosis for diseases like SPS.

With more research, scientists can uncover the reason for these links, potentially unlocking important discoveries about other autoimmune diseases and movement disorders as well. We know that discovering causes and cures for one brain disease often leads to critical insights and breakthroughs in other areas. That’s why we support research across the whole spectrum of brain diseases and disorders—because we know that when we cure one, we will cure many.

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