What are the other Names for this condition? (Also known as/Synonyms)

• Classic Stiff Person Syndrome
• Moersch-Woltman Syndrome
• SPS (Stiff Person Syndrome)

What is Stiff Person Syndrome? (Definition/Background Information)

• Stiff Person Syndrome (SPS) is an extremely rare, acquired autoimmune and neurological disorder involving the trunk, arms, and legs that results in alternating muscle rigidity (stiffness) and muscle spasms. The spasms can occur randomly or be induced by certain stimuli (triggers such as cold temperatures, loud noise, and stress). SPS is also termed the classic form (of Stiff Person Syndrome)
• The stiffness begins in the lower back or legs. As the condition progresses, the stiffness can be more visible on one side than the other. This asymmetrical stiffness results in difficulty in walking, alteration of body posture, and difficulty in maintaining balance. The stiffness can progress to involve the arms and facial muscles over time
• Middle-aged women are at a higher risk for the condition. The risk factors for Stiff Person Syndrome may include other autoimmune disorders such as diabetes type 1, vitiligo, and pernicious anemia. Presently, the cause of formation of the condition is not well-understood
• The diagnosis of Stiff Person Syndrome is generally challenging due to its extreme rarity. However, blood tests and cerebrospinal fluid tests for detecting anti-GAD antibodies may aid in the diagnosis
• Following a diagnosis, the treatment of Stiff Person Syndrome is mostly symptomatic and may involve medications, such as muscle relaxants and corticosteroids, immunotherapy, physical therapy, and stress management. Nevertheless, there is no cure for Stiff Person Syndrome
• The prognosis of Stiff Person Syndrome depends primarily on its severity and response of the individual to treatment. Individuals with milder signs and symptoms generally have better outcomes than those with severe forms of Stiff Person Syndrome

Experts believe that there are several variants of Stiff Person Syndrome depending on the pattern of signs and symptoms and parts of the body involved. The variants include:

• Stiff Limb Syndrome: In this type, usually one leg is involved with localized stiffness and muscle spasms. Over time, the signs and symptoms may involve both the legs. This condition is also known as focal or partial Stiff Person Syndrome
• Jerking Stiff-Person Syndrome: In this type, individuals have muscle stiffness and spasms affecting the legs; additionally, there is brainstem involvement causing sudden involuntary jerking of a group of muscles referred to as positive myoclonus, or there may be relaxation of a group of muscles, termed negative myoclonus
• Progressive Encephalomyelitis with Rigidity and Myoclonus (PERM): It is often characterized by signs and symptoms similar to Classic Stiff Person Syndrome. In this subtype, the signs and symptoms progress more rapidly (usually over several weeks). Additionally, there may be dizziness (vertigo), loss of balance, difficulty in speaking (dysarthria), difficulty in swallowing (dysphagia), involuntary eye movement (nystagmus), and paralysis of eye muscles (ophthalmoplegia) due to cranial nerve involvement
• Paraneoplastic-Related Stiff Person Syndrome: This type is noted in individuals who have signs and symptoms similar to Classic Stiff Person Syndrome in individuals with underlying malignancies, commonly lung cancer and breast cancer

Who gets Stiff Person Syndrome? (Age and Sex Distribution)

• Stiff Person Syndrome is an extremely uncommon condition with an incidence rate of 1-2 cases per million population
• It is usually diagnosed in individuals in the 30-60 years’ age range. Rarely, it has been reported in children
• Even though both genders are affected, a female predominance is observed (female-male ratio is 2:1)
• Worldwide, there are no racial or ethnic group preferences noted

What are the Risk Factors for Stiff Person Syndrome? (Predisposing Factors)

The risk factors for Stiff Person Syndrome (SPS) may include:

• Individuals with SPS have been associated with other autoimmune disorders such as:
  • Autoimmune thyroiditis
  • Pernicious anemia
  • Type 1 diabetes
  • Vitiligo
• Association with malignancies: Individuals with SPS have a higher incidence of the following cancers:
  • Breast cancer
  • Lung cancer
  • Kidney cancer
  • Thyroid cancer
  • Colon cancer
  • Different types of lymphomas

The cause of increased incidence of Stiff Person Syndrome with these (above) malignant conditions is presently unknown.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Stiff Person Syndrome? (Etiology)

The cause of development of Stiff Person Syndrome (SPS) is presently not well-established.

• Researchers believe that it is caused by an abnormal autoimmune reaction wherein the body’s own immune cells attacks nerve cells in the brain that are responsible for muscle control and movement
• Specifically, the immune system attack the protein glutamic acid decarboxylase (GAD), which helps in the production of a neurotransmitter called gamma-aminobutyric acid (GABA)
• GABA helps regulate motor neurons of the body reducing their activity. When GABA levels are low, it results in the motor neurons firing uncontrollably, resulting in muscle spasms and stiffness
• Approximately, 60-80% of individuals with Stiff Person Syndrome are known to have GAD antibodies in their blood and cerebrospinal fluid (CSF)

Stiff Person Syndrome is also considered to be a type of neurological movement disorder.

What are the Signs and Symptoms of Stiff Person Syndrome?

The signs and symptoms of Stiff Person Syndrome may vary from one individual to another and can be mild or severe. The onset of signs and symptoms are generally noted over a period of several months.

These may include:

• Stiffening of back, arm, and leg muscles
• There can be episodes of severe painful muscle spasms
• Progression of the signs and symptoms: These episodes of muscle stiffness and painful muscle spasms get worse over time
• Abnormal body postures such as hunched-over back
• Walking can be difficult
• Spasms of the neck can result in loss of voice
• It is observed that during sleep, the frequency of muscle contractions decrease significantly

The rigidity and spasms may be sporadic in their occurrence, or be triggered by any of the following triggers:

• Loud noise, such as street noise/horn noise, which may be unexpected
• Touch
• Sudden movement
• Emotional distress
• Cold environments

It is important to note that in a vast majority of individuals, neurological signs and symptoms do not occur.

How is Stiff Person Syndrome Diagnosed?

An early diagnosis of Stiff Person Syndrome (SPS) is important for availing immediate and appropriate treatment. However, the diagnosis of SPS is often difficult due to its rarity.

The diagnosis may be undertaken via the following tests and exams:

• A thorough physical examination and medical history evaluation
• Assessment of the presenting signs and symptoms
• Blood tests for anti-GAD antibodies
• Cerebrospinal fluid tap: Analysis of CSF fluid for anti-GAD antibodies
• Electromyography (EMG)
• Imaging studies as needed

It is important to exclude disorders with similar signs and symptoms by undertaking a differential diagnosis for the following:

• Parkinson’s disease (PD)
• Multiple sclerosis (MS)
• Fibromyalgia
• Anxiety and phobia

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Stiff Person Syndrome?

The complications of Stiff Person Syndrome may include:

• Walking can be so severely affected that it is considered a disability
• The episodes of spasms can result in uncontrolled falls leading to injuries
• Spasms of the chest muscles may cause acute difficulty in breathing. In such situations, emergency ventilatory support may be required
• Severe depression and anxiety
• Social phobia
• Severe signs and symptoms can affect an individual’s ability to carry out their daily activities
• One's overall quality of life may be severely affected

Sudden death can occur due to apnea (stoppage of breathing).

How is Stiff Person Syndrome Treated?

Presently, there is no cure for Stiff Person Syndrome (SPS) and a symptomatic management of the disorder is undertaken. For individuals with SPS, a multi-disciplinary treatment plan involving specialists, such as internists, orthopedists, neurologists, and family medicine practitioners, which is customized to the individual, is often necessary to improve their quality of life.

The treatment measures for Stiff Person Syndrome may include:

• Medications such as muscle relaxants, sedatives, and steroids
• Physical therapy (PT) and occupational therapy (OT)
• Aquatherapy
• Immunosuppressant therapy using oral medications
• immunomodulating therapies including intravenous immunoglobulin (IVIG) therapy and plasmapheresis
• Stress management and counselling
• Rehabilitation therapy
• Periodic health checkups and regular physician visits are important and recommended

The treatment plan may also involve taking suitable measures to protect the affected individuals from the known triggers.

Clinical trial studies for Stiff Person Syndrome for new test procedures and treatment methods are underway. Please check suitable government websites for relevant information on the same.

How can Stiff Person Syndrome be Prevented?

Currently, there are no available preventive measures for Stiff Person Syndrome.

• Avoiding the known triggers may be helpful in controlling episodes of muscle rigidity and spasms
• Undertaking adequate treatment of any underlying/associated conditions is important and beneficial
• In some individuals, medications can slow or even stop progression of the condition for a certain period of time

What is the Prognosis of Stiff Person Syndrome? (Outcomes/Resolutions)

The prognosis of Stiff Person Syndrome may vary from one individual to another and mainly depends on the severity of signs and symptoms and one’s response to therapy.

• The outcomes also depend on the nature of any underlying autoimmune disorder associated with the condition
• There is no cure for Stiff Person Syndrome and treatment is generally symptomatic. With prompt and adequate treatment, the outcomes may be improved

Additional and Relevant Useful Information for Stiff Person Syndrome:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/health-topics/orthopedc-disorders/