Stiff Man Syndrome

By | June 10, 2022

Stiff Man Syndrome (SMS) is a rare autoimmune disease that affects the central nervous system and endocrine glands. It is characterized by a permanently increased muscle tone of the back and hip muscles. The syndrome can occur spontaneously or as a paraneoplastic syndrome.

What is Stiff Man Syndrome (SMS)?

Stiff Man Syndrome is a very rare condition characterized by gradual stiffening of the muscles. The back and hip muscles are mainly affected. However, the leg muscles and even the arm muscles can also become stiff. It is usually a disease of the lower extremities, with symmetrical involvement of the corresponding muscle groups. In the case of a paraneoplastic syndrome, the disease can also begin in the arm muscles. For what is hyperkalemia used for, please visit

It is an autoimmune disease of the central nervous system and endocrine glands. Therefore, increased muscle tone and hormonal disorders are often present at the same time. The name stiff man syndrome comes from the translation “stiff man” for “stiff man”. For some time now, the disease has also been referred to by the neutral term stiff-person syndrome.

Stiff-man syndrome or stiff-person syndrome is characterized by the occurrence of several variants. In addition to classic SMS, there is also stiff leg syndrome (SLS) with stiffening of the leg muscles, progressive encephalomyelitis with rigidity and myoclonus (PERM) and paraneoplastic SMS.

While paraneoplastic stiff man syndrome is the result of cancer, classic SMS occurs spontaneously. There are also disease developments in which SLS progresses to SMS and finally to progressive encephalomyelitis.


The cause of stiff man syndrome is an autoimmune process affecting the nervous system and endocrine glands. Antibodies against the enzyme glutamate decarboxylase, which is responsible for the synthesis of gamma-aminobutyric acid (GABA), are found in most patients. GABA is a neurotransmitter that has a modulating effect on the nervous system. It has calming and anxiolytic effects.

Antibodies against glutamate decarboxylase are also found in other autoimmune diseases such as type 1 diabetes. This is why stiff man syndrome often occurs with other hormone-related diseases. Another variant of SMS results from cancer of the breast or lungs.

In addition to inhibiting GABA, paraneoplastic SMS also produces antibodies against the enzyme amphiphysin. This enzyme is involved in the cell growth of nerve cells. The restriction of the function of glutamate decarboxylase and amphiphysin explains the neurological symptoms of the disease.

Symptoms, Ailments & Signs

Stiff man syndrome is characterized by a variety of symptoms that are motor, autonomic, psychiatric, orthopedic, or endocrinological in nature. The main symptom is an increasing chronic increase in tone of the back and lumbar muscles. The motor changes in this condition are characterized by gait disturbances, rigidity (stiffness), increased intrinsic reflexes, spasms, and frequent falls while fully conscious.

Vegetatively, the symptoms express themselves in frequent sweating, dilation of the pupils, high blood pressure, increased heart rate and breathing difficulties. Psychiatric symptoms in the form of anxiety attacks and increased startleiness can be added to banal external stimuli.

Orthopedic symptoms include the occurrence of hyperlordosis, joint stiffness, constant dislocation of joints and spontaneous fractures. Finally, stiff man syndrome is often associated with endocrine diseases such as type 1 diabetes mellitus and thyroid diseases (overactive and underactive).

Diagnosis & course of disease

A large number of examinations are required to diagnose the disease. These are based on the anamnesis of the medical history, electromyographic examinations, clinical neurological examinations and the detection of antibodies and autoantibodies. In the electromyographic examination, the tone of the muscles is determined.

This is also increased in the presence of the syndrome when the patient tries to relax. Furthermore, antibodies against the enzyme glutamate decarboxylase are found in 60 to 90 percent of all patients. In the case of paraneoplastic SMS, antibodies against the enzyme amphiphysin also appear. If these antibodies are found, a search for the underlying cancer follows.

However, since antibodies against glutamate decarboxylase as well as against amphiphysin also occur in other diseases, the usefulness of this test in clarifying stiff-man syndrome is often questioned.


Stiff Man Syndrome is an insidious disease that causes serious physical and mental complications as the disease progresses. Gait disorders, spasms, rigidity and other typical movement disorders are always associated with an increased risk of accidents. Those affected often suffer psychologically as a result of these symptoms – fears develop and social life is reduced further and further.

Symptoms such as frequent sweating and anxiety attacks also contribute to this isolation. High blood pressure and breathing difficulties promote an increased risk of cardiovascular disease. In extreme cases, patients who are already suffering from another heart disease can suffer a heart attack.

Furthermore, stiff man syndrome can lead to neurological deficits and a decrease in mental abilities. In the later stages, bone fractures occur spontaneously and joints are dislocated again and again. The treatment of these complaints is often lengthy and even associated with serious complications.

Drug treatment with baclofen or benzodiazepines is extremely risky, since the active ingredients can lead to serious interactions. Surgical treatment of the fractures is difficult due to the risk of further spasms.

When should you go to the doctor?

With stiff man syndrome, the affected person is dependent on medical treatment by a doctor. It is a serious disease that cannot heal itself. If the disease is not treated properly, it can lead to serious complications that can significantly restrict the everyday life of those affected. Therefore, a doctor should be consulted at the first symptoms of stiff man syndrome. A visit to a doctor is necessary if the person concerned suffers from severe gait disorders.

As a rule, restrictions in movement occur, which make everyday life difficult for the patient. Furthermore, a doctor should also be consulted if profuse and excessive sweating occurs, with most sufferers also suffering from high blood pressure. It is not uncommon for stiff joints or muscle complaints to indicate stiff man syndrome and must also be examined by a doctor.

The syndrome is then treated by a general practitioner or by an orthopedist. Whether the syndrome can be completely cured cannot be universally predicted. As a rule, stiff man syndrome does not reduce the life expectancy of the person affected.

Treatment & Therapy

Although the cause of stiff man syndrome is largely unknown, surprising success has been achieved in treating the condition. Two therapeutic approaches are considered. On the one hand, drug treatment with benzodiazepines or baclofen increases the inhibition of the nervous system that is dependent on gamma-butyric acid (GABA).

With it, muscle stiffness, cramps and anxiety attacks can be kept under control. On the other hand, an attempt is also made to reduce the actual autoimmune reaction of the immune system against the nervous system and the endocrine system by weakening the immune system. For this purpose, immunosuppressive drugs such as methylprednisolone or rituximab are administered.

Furthermore, the infusion of intravenous immunoglobulins or plasmapheresis also serves this purpose. If antibodies against amphiphysin are found, further therapeutic steps are necessary in addition to these measures. Since these antibodies give an indication of the possible presence of cancer, the type of cancer must first be diagnosed and then treated accordingly. Only then is the successful therapy of the paraneoplastic stiff-man syndrome possible.


Since the causes of stiff man syndrome are not known, no concrete recommendations for its prevention can be given. Of course, a healthy lifestyle with plenty of exercise and a balanced diet can generally reduce the risk of the disease. This applies both to the spontaneous occurrence of the disease and to its development as a result of a carcinoma.


So far, there is no cure for sufferers of stiff man syndrome. Therefore, aftercare in the classic sense is neither necessary nor possible for this disease. The severity of the muscle stiffness and the course of the disease can manifest themselves differently in the affected patients. There are also different therapeutic approaches. For this reason, no general statements can be made about any aftercare measures.

In almost all cases, intensive psychotherapeutic care is necessary, since patients with stiff man syndrome are often affected by anxiety and depression. In addition, it is fundamentally necessary to continue to monitor the course of the disease and the tolerability of the drug treatment. This can be done by a specialist or general practitioner.

The attending doctor decides on the intervals between the check-ups and the necessary follow-up measures. Depending on the form and course of the stiff man syndrome, these can be extremely different. In children, the disease is usually milder, although there are only a few long-term studies on it. As a rule, they still need medical care for the rest of their lives. Regular check-ups are usually necessary.

Since patients with stiff man syndrome have an increased risk of developing diabetes, it is advisable to check their blood sugar levels regularly in most cases. In addition, those affected should ensure a balanced and healthy diet.

You can do that yourself

The stiff man syndrome is initially treated with medication or surgery. Depending on the therapy, the patient can take some measures himself to support the medical treatment.

First of all, the seizures must be noted in detail so that the treating neurologist can work out clues for a possible therapy. The prescribed medication must be taken according to the doctor’s instructions and the intake should also be carefully documented with regard to any side effects and interactions. In the case of severe neurological damage, alternative measures such as participation in special therapies or a visit to a neurological rehabilitation clinic may also be indicated.

However, the stiff man syndrome cannot yet be completely cured. Accordingly, the patient himself must decide on any surgical measures to at least alleviate the symptoms.

Movement disorders and other complaints can occur after an operation, which must be treated individually. Depending on the extent of the intervention, further care in a specialist clinic may then be necessary. The patient should best consult a specialist for this. Accompanying the treatment of the physical complaints, therapeutic treatment is also useful in the case of stiff man syndrome.

Stiff Man Syndrome