Stiff-Person-Syndrome (SPS): Symptoms, Causes & Treatment Options

The Stiff-Person-Syndrom (SPS) is a rare and complex autoimmune disorder of the central nervous system characterized by unpredictable muscle rigidity and painful spasms. The condition, which affects more women than men, gained wider recognition when singer Céline Dion publicly disclosed her diagnosis in 2022. While not fully understood, advancements in diagnosis and treatment offer hope for managing symptoms and improving quality of life for those affected.

What is the Stiff-Person-Syndrom (SPS)?

The name “Stiff-Person-Syndrom” originates from the primary symptom: muscles involuntarily stiffen and cramp. The exact cause remains unclear, but it’s believed to stem from an autoimmune response. Individuals with SPS often experience limitations in daily activities, with symptoms potentially worsening, changing, or fluctuating over time.

Who is Affected?

Previously known as Stiff-Man-Syndrom, it’s now understood that women are twice as likely to be affected as men. SPS is a neurological dysfunction primarily impacting individuals between the ages of 40 and 50, though it can occur in children and older adults.

It’s estimated that approximately one in a million people are affected, making it a very rare disease. However, experts suggest the actual prevalence may be higher due to frequent misdiagnoses. A study of 199 individuals with SPS revealed that 73.9 percent had initially received an incorrect diagnosis.

Possible Symptoms of Stiff-Person-Syndrom

People with SPS experience increased muscle tension, hardening of muscles, stiffness and sudden, painful muscle cramps triggered by stimuli like light touch, loud noises, startle, or cold temperatures. These symptoms often occur in episodes but can become more frequent or intense over time. Muscle stiffness is typically concentrated in the trunk and limbs, though it can occasionally affect the neck and face. The exaggerated muscle tension often leads to an abnormal posture, with individuals leaning backward (hyperlordosis) and experiencing a stiff, awkward gait, increasing the risk of falls and subsequent injuries.

Further Symptoms

• Increased sensitivity to stimuli such as noise, touch, and emotional stress
• Anxiety and depression
• Overactive reflexes and uncontrolled muscle twitching
• Chronic pain
• Shortness of breath if muscles in the chest are affected
• Speech disturbances if muscles in the larynx are affected
• Impaired vision, leading to double vision, difficulty speaking, and reduced coordination

Anxiety and Depression: A Vicious Cycle

The constant fear of unpredictable spasms, often triggered by noise, shock, cold, or even slight touch, places individuals in a state of perpetual psychological tension. This tension isn’t solely a reaction to pain but is exacerbated by a deficiency in GABA, a neurotransmitter that normally regulates anxiety and calms the nervous system. With the nervous system in a constant state of hyper-excitability, emotional stress further worsens muscle rigidity.

many patients develop agoraphobia, fearing loss of control in public due to sudden spasms. Because muscles can stiffen abruptly, the risk of severe falls and injuries is high, leading to further social withdrawal.

What Causes the Condition?

The precise causes and mechanisms of SPS are not yet fully understood. It’s believed to be an autoimmune disorder where the body’s immune system attacks healthy tissue or messengers. This is more common in women. Most individuals with SPS have antibodies in their blood that their body produces.

These antibodies primarily attack an enzyme called Glutamate Decarboxylase (GAD), crucial for the function of inhibitory synapses in the nervous system. When this inhibition is reduced, the nervous system becomes overstimulated, leading to muscle cramps. This also contributes to psychological symptoms like anxiety and depression. Beyond antibodies against GAD, other antibodies attack different proteins and enzymes, leading experts to now refer to SPS as the “Stiff-Person-Spectrum-Disorder.”

SPS is often associated with other autoimmune conditions, including Type-1 Diabetes, thyroid diseases, pernicious anemia, and, less frequently, vitiligo. In less than five percent of cases, individuals with SPS are diagnosed with cancer, typically breast or lung cancer, years after the initial symptoms. This subtype is known as paraneoplastic Stiff-Person-Syndrom. A genetic predisposition is also suspected, making individuals more susceptible to autoimmune diseases. Infections and environmental factors may also play a role.

What Types of SPS Are There?

Based on symptoms, different types of SPS are diagnosed, leading to the term “Stiff-Person-Spectrum-Disorder.” The type determines the treatment approach. The classifications include:

Classical Stiff-Person-Syndrom

This is the most common form, characterized by stiffness and cramps in the muscles of the lower back, legs, and sometimes the abdomen. Affected individuals often have a stiff gait and experience pain throughout the day.

Focal or Segmental SPS

This rare form combines classical features with symptoms indicating dysfunction in the brainstem or cerebellum. Individuals with SPS Plus may experience muscle cramps, stiffness, and coordination difficulties, as well as double vision and slurred speech.

Other SPS Types

Even rarer forms include progressive encephalomyelitis with rigidity and myoclonias (PERM), which progresses rapidly and causes painful cramps. Other syndromes can overlap with SPS, presenting symptoms and findings indicative of dysfunction in the brainstem, cerebellum, spinal cord, and brain.

What are the Risk Factors?

Because the cause of SPS is not fully defined, the risk factors are not well-researched. Gender appears to be a significant factor, with women being almost twice as likely to develop SPS as men. Other autoimmune diseases, environmental factors, and infections could also play a role.

How is the Condition Diagnosed?

Diagnosing SPS can be challenging and may take years due to the complexity and rarity of the condition, as well as the non-specific and variable nature of the symptoms. A clinical neurological examination, along with typical changes in affected muscles, can identify muscle stiffness and reflex changes. Electrophysiological tests examine the abnormal electrical activity of muscles and nerve impulse transmission, such as through electromyography. These tests help assess the nervous system’s overexcitability.

In some cases, other symptoms are ruled out using MRI of the brain and spinal cord. Blood tests and tests of the cerebrospinal fluid (“nerve water”) help identify specific antibodies associated with SPS, particularly anti-GAD antibodies. While not always present, their detection can support the diagnosis. However, these antibodies can also be found in some healthy individuals.

Treatment of the Condition

Currently, there is no cure for SPS. However, individualized therapy can alleviate symptoms and improve quality of life. Treatment focuses on two pillars: combating the underlying autoimmune disorder and treating the muscle overexcitation.

Immunosuppressive medications, such as corticosteroids, other immunosuppressants, or immunoglobulins, are used to suppress the immune response. Plasmapheresis (“blood washing”) may be used to attempt to remove antibodies through filtration.

Muscle overexcitation can be treated with medications that promote muscle relaxation, primarily benzodiazepines, often in high doses. If physical symptoms are triggered by anxiety, serotonin reuptake inhibitors, also used to treat depression, may be used.

Immunobased therapies include intravenous or oral immunosuppressive medications and immunoglobulins, and less frequently, plasma exchange. Alongside medication, muscle-relaxing measures such as physiotherapy, hydrotherapy, yoga, Pilates, massage, acupuncture, and behavioral therapy can be helpful.

Prognosis and Life Expectancy

Although SPS is incurable, it typically doesn’t prove fatal and doesn’t necessarily reduce life expectancy. In rare cases, muscle cramps affecting the chest can impair breathing. However, the condition can significantly impact individuals, potentially leading to wheelchair dependence or bedridden status. Fatal complications arise from consequences of SPS, such as blood clots or wound infections due to immobility. Risks also include complications and fractures from severe falls. Life expectancy is often influenced by co-occurring autoimmune diseases like Type-1 Diabetes.

Can SPS Be Prevented?

Currently, the German Brain Foundation states Notice no preventative recommendations for SPS. However, general recommendations to potentially reduce the risk of autoimmune diseases exist, including a healthy lifestyle with a balanced diet, regular physical activity, and sufficient sleep. Stress, smoking, and infections can increase the risk of autoimmune reactions. Regular medical check-ups, especially when abnormalities are present, can help detect and treat potential symptoms and conditions early.

Frequently Asked Questions

What are the first signs of Stiff-Person-Syndrom?

The initial signs of SPS often include increased muscle tension, stiffness, and painful muscle cramps, particularly in the trunk and limbs. These symptoms can be triggered by stimuli like noise, touch, or emotional stress.

Is Stiff-Person-Syndrom fatal?

While SPS is not typically fatal, it can lead to serious complications, such as respiratory problems or injuries from falls, which can be life-threatening in rare cases. The condition can significantly impact quality of life.

Is there a cure for Stiff-Person-Syndrom?

Currently, there is no cure for SPS. However, treatments are available to manage symptoms and improve quality of life, including immunosuppressants and muscle relaxants.