Stiff person syndrome (SPS) is considered dangerous in babies because they generally meet unfortunate and untimely death within a few months. The normal lifespan of a grown adult can be stated as 50 years (if symptoms start early). Patients typically present with initial symptoms between 40 and 60 years, although the onset has been reported in patients who are younger than 40 years and older than 60 years. From symptom onset to death, the course of SPS can range from 6-28 years.
Although the treatment for SPS is available, it does not cure the syndrome. Many patients have a slow course of the disorder that is mostly without symptoms, punctuated by occasional episodes of stiffness. Other patients may have a much more aggressive course, rapidly progressing to the late stages of the disease.
The average life span is often challenged and depends on the individual and course of the treatment. In SPS, life expectancy usually depends on the criticality of the syndrome, and death still remains an unpredictable factor. In this condition, patients are generally injury-prone and that reduces their lifespan by a considerable amount.
The frequency of SPS worldwide or in the United States is unknown, but the syndrome is rare. The syndrome also occurs in children younger than three years, and the onset in adults is most frequent in the third to fifth decades of life.
What is stiff person syndrome?
Stiff person syndrome/Moersch–Woltmann syndrome or SPS is an extremely rare and progressive neurological disorder that impacts the nervous system of the body. The disorder generally impacts the spine and extreme lower parts of the body. The disorder is often stimulated by emotional stress. In some cases, the muscles of the neck, trunk, and shoulders may also be involved. SPS may begin as recurring (intermittent) episodes of stiffness and spasms, often precipitated by surprise or minor physical contact. Symptoms may occur gradually, spreading from the back and legs to involve the arms and neck. Abnormal postures, often hunched over and stiffened, are characteristic of the disorder; other signs and symptoms include:
- Heightened sensitivity to stimuli such as noise, touch, and emotional distress
- Deprived sleep and rapid eye movement due to pain
- Muscle stiffness in the trunk and limbs that comes and goes
- Back stiffness or pain
- An exaggerated upright posture
- Stiff-legged walk
- Severe muscle spasms in the arms and legs when the person is startled, touched, upset, or anxious
- Lordosis (curved lower back) and deformed joints in the body, over time
- Falling during sudden muscle spasms (may cause additional related problems)
- Abnormally slow and wide gait pattern in an effort to maintain balance
- The appearance of an emotionless mask (rare in SPS)
- Limited chest expansion, leading to difficulty breathing
- The cause of SPS is unknown, but it is an autoimmune disorder (malfunction of the immune system, where the body produces antibodies against its own tissues).
- Most patients with SPS have antibodies against glutamic acid decarboxylase (GAD), the enzyme involved in the production of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), an enzyme largely found in the central nervous system. GAD is a GABA-synthesizing enzyme, with two primary iso-forms GAD-65 and GAD-67. GAD-65 is primarily associated with SPS; it is also associated with diabetes mellitus, cerebellar ataxia, and limbic encephalitis. When GAD is inhibited by the anti-GAD in SPS, GABA becomes less readily available, thus reducing GABA’s inhibitory effect. This process leads to continuous stimulation of muscles by motor neurons, resulting in muscle rigidity.
How is stiff person syndrome treated?
Physical therapy and occupational therapy play an important part in managing stiff person syndrome (SPS) and may help with side effects of medications (such as weakness) in addition to controlling symptoms of the disease. Treatment aims to control symptoms and improve mobility and function. Treatment options depend on the symptoms and severity of each person and may include:
- Benzodiazepines: They are generally considered the best initial therapy for SPS. Examples include diazepam and clonazepam. These usually slow down the nervous system and may relieve muscle spasms and anxiety. Baclofen, a muscle relaxant, may be used for people in whom benzodiazepines are not effective or not well-tolerated. Some people benefit from using baclofen in addition to benzodiazepines.
- Corticosteroids: These are reportedly effective but have many long-term adverse effects.
- Immune-modulating therapies: These are usually considered in people with severe symptoms who do not experience relief with benzodiazepines and baclofen. Options may include intravenous immunoglobulin (IVIg) therapy, plasmapheresis (also called plasma exchange), and rituximab. However, studies supporting the effectiveness and safety of these therapies for SPS are limited.