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Stiff-Person Syndrome

Two neurologists explain the science behind stiff-person syndrome.

Two neurologists explain the science behind it

The announcement by celebrated singer Celine Dion in early December 2022 that she has stiff-person syndrome—a rare neurological disorder—stunned the world and led to an outpouring of support for the French Canadian star.

Until Dion’s revelation, most people had probably never heard of the condition. Worldwide, stiff-person syndrome affects only about 1 in a million people, mostly between the ages of 20 and 50, with twice as many women as men having the disorder.

First reported in 1956, the classic and most common form of stiff-person syndrome is characterized by painful and fluctuating stiffness, mostly in the muscles of the trunk, including the back and abdomen and upper legs. Patients also experience painful muscle spasms, sometimes triggered by touch or noise.

The onset of the disorder is usually gradual, and those who suffer with it may experience progressive worsening of their symptoms. The experience of living with stiff-person syndrome varies from person to person, as it depends on the severity of symptoms and one’s response to treatment. Ultimately, stiff-person syndrome can affect the ability to walk, increasing the risk of falls and the need for assistance with a cane, walker or wheelchair.

We are specialized neurologists who treat patients with movement and neuroimmunological disorders. Because stiff-person syndrome is so rare, patients typically will receive extensive testing by multiple doctors before being diagnosed with the condition. In our experience, it is not uncommon for us to be the third or fourth doctor whom individuals seek out for an evaluation and diagnosis.

Biological underpinnings
Stiff-person syndrome is different from other neurological disorders like Parkinson’s disease or multiple sclerosis. Although in each of these conditions people can experience stiffness and cramps, the underlying cause of symptoms is different in all three.

Stiff-person syndrome is an autoimmune disorder—a broad term to describe when the body’s natural defense system mistakenly attacks the person’s own body.

In the late 1980s, researchers discovered what are known as “auto-antibodies” related to stiff-person syndrome. Antibodies are a critical part of the body’s defense system to help fight off infection or anything that appears to be foreign. So auto-antibodies are those that mistakenly target specific receptors, cells or organs of one’s own body. But it was the discovery of one key auto-antibody that gave physicians important insights into the disease process of stiff-person syndrome and how to manage it with various medications and immunotherapy.

The human nervous system is comprised of various pathways that prevent too much or too little muscle activation. An enzyme called glutamic acid decarboxylase, or GAD, helps convert a neurotransmitter­—a chemical that nerve cells use to communicate— called glutamate to gamma-aminobutyric acid, or GABA. This process plays an important role in preventing excessive muscle activity.

Researchers have found that 60% to 80% of people with classic stiff-person syndrome have elevated levels of the auto-antibody called anti-GAD. Antibodies against GAD prevent the formation of GABA, which can then lead to excessive muscle activity such as stiffness.

While anti-GAD appears to be the most common auto-antibody in those with classic stiff-person syndrome, recent discoveries have revealed additional antibodies that can also result in the condition.

Treatment options
To date, there is no cure for stiff-person syndrome. Current treatments are aimed at improving the stiffness and spasms, and modulate the immune system.

Different types of muscle relaxants are used to treat the muscle tightness and spasms. And some anticonvulsants, used to treat epilepsy, have also been shown to reduce muscle spasms.

Doctors may also use treatments that target the immune system. Evidence is accumulating that one treatment, known as intravenous immunoglobulins, may be effective. Immunoglobulins, or antibodies, collected from thousands of healthy donors are given intravenously at regular intervals to patients with stiff-person syndrome to help improve their symptoms.

Alternate treatments for those who do not respond to these approaches may include antibody therapy with the drug rituximab, or a procedure called plasma exchange in which the auto-antibodies are filtered out. However, evidence for the effectiveness of these therapies is lacking.

Living with the diagnosis
Doctors like us still have a lot to learn about stiff-person syndrome, but increasing awareness of this condition may lead to a more timely diagnosis and help accelerate research. And as more people learn about it, they may be more likely to recognize the symptoms and seek treatment earlier.

Patients with milder disease or those who respond well to treatment may continue functioning independently while they continue medical therapy. For others, symptoms may not be completely controlled and could lead to disability.

We recognize that the journey to a diagnosis of stiff-person syndrome can be challenging and receiving the diagnosis can be life-altering. But through capable teams of doctors and other support systems for people who are diagnosed with stiff-person syndrome, researchers like us hope to help patients continue living life to the fullest.

Bhavana Patel receives funding from National Institute on Aging and Mangurian-Fixel-McKnight Collaboration for Pilot Studies in Lewy Body Dementia. She has received a training grant from the American Brain Foundation and the Mary E. Groff Charitable Trust.

Torge Rempe received grant funding from the National Multiple Sclerosis Society. Dr. Rempe has grant/contract research support from Sanofi, Novartis, Celgene, and Genentech.

Source: The Conversation • Photos:

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