Myasthenia gravis

Sophie Matzik is a freelance writer for the medical team.

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Myasthenia gravis is a nervous disease in which the transmission of signals between the nervous system and muscles is impaired. The causes are so far unclear. Myasthenia gravis is manifested by muscle weakness, which can be slightly different for each person affected. Symptomatic therapy is possible, but the disease is not curable. Read everything you need to know about myasthenia gravis here.

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. G70

Myasthenia gravis: description

Myasthenia gravis is a neurological disease that is characterized by muscle weakness or the failure of individual muscles. The transmission of signals between the nervous system and the muscles is disturbed. Myasthenia gravis leads to symptoms that are not continuously pronounced, in which individual muscles or muscle groups are alternately weakened or can no longer be moved (especially in the face). The weakness can appear spontaneously or it can increase slowly over the course of the day. How the signal transmission is disturbed is still unclear.

Myasthenia gravis is a relatively rare condition. On average, around 100 to 200 out of a million people get it. In general, myasthenia gravis can occur at any age. However, the 20 to 30 year olds and the 60 to 80 year olds are particularly often affected. Women get myasthenia gravis slightly more often than men. The number of reported illnesses has increased significantly in recent years. According to scientists, this increase is not due to an increase in actual cases of the disease, but rather to the greater awareness of myasthenia gravis.

Once the disease has developed, it will persist for a lifetime, with those affected sometimes being more and sometimes less affected by the muscle weakness. Therapy and prognosis depend on the stage at which the disease is recognized. Myasthenia gravis is not curable, only the symptoms can be relieved with medication.

By the way, dogs can also get myasthenia gravis.

Myasthenia gravis: symptoms

The symptoms that occur with myasthenia gravis are many and vary from patient to patient. In general, various muscles and muscle groups of the skeleton (striated muscles) are impaired by the muscle weakness, in which movements can be carried out with less force or less accuracy. The heart muscle and the muscles of the internal organs are not affected by myasthenia gravis because they belong to a different muscle type (smooth muscles) and are supplied with signals differently.

In principle, myasthenia gravis can extend to all skeletal muscles. At the beginning of the disease, only smaller muscles are usually affected. In the morning and after rest, the symptoms are often weaker, in the evening and after physical exertion they usually become stronger.

In about half of all those affected, the first symptoms become noticeable on the face, especially in the eyes. Those affected often suffer from the so-called bedroom view, in which the upper lid of the eye hangs down and can no longer be lifted willingly (ptosis). People often report double vision or the inability to close their eyes completely. Also in the initial phase, the facial muscles are often affected by the muscle weakness. Patients have difficulty closing their mouths properly, laughing, chewing, or speaking. The neck muscles are also often compromised, making it difficult for patients to keep their heads upright.

If the muscle weakness spreads to the chewing and throat muscles, problems with eating and swallowing arise first. It becomes dangerous with severe paralysis, as it is then impossible to swallow one's own saliva. In the advanced stage, the inability to swallow can go so far that the affected person has to be artificially fed and the saliva must be sucked off regularly.

If the limbs are affected by myasthenia gravis, symptoms in the arms are often more severe than in the legs.

Myasthenia gravis: complications

Myasthenia gravis becomes life-threatening when the respiratory muscles are impaired. Mechanical ventilation is necessary in the event of severe disease. Swallowing disorders can also lead to complications, for example if something swallowed gets into the lungs instead of the esophagus. As a result, pneumonia (aspiration pneumonia) often occurs.

To make matters worse, especially in older people, myasthenia gravis symptoms are often misinterpreted or not properly considered. In many cases, this means that treatment starts too late or not at all, which means that the symptoms continue to worsen.

Myasthenic crisis

Medical professionals describe a sudden deterioration in the condition of myasthenia gravis patients with severe swallowing disorders and breathing problems as myasthenic crisis. Those affected must be treated as inpatients; even with treatment in an intensive care unit, the risk of dying from a myasthenic crisis is still five percent. The causes of a myasthenic crisis are infections, mistakes in taking medication (e.g. too low a dosage) and stopping therapy too early.

Myasthenia gravis: causes and risk factors

To date, the causes of myasthenia gravis have not yet been fully clarified. It is known that myasthenia gravis is one of the autoimmune diseases. This means that the immune system forms defensive substances (antibodies) against the body's own structures, which destroy them.In myasthenia gravis, antibodies are formed which destroy the docking points (receptors) for certain neurotransmitters, thereby hindering the transmission of signals in the body.

In order to transmit a signal from the brain to the muscles, the signal is recoded at the end of a nerve, i.e. the electrical signal in the nerve now becomes a chemical signal that excites the muscles. For this purpose, messenger substances (transmitters) are released. These bind to specific docking sites (receptors) on the muscle cells. In this way the muscle is excited, it contracts and thus enables a certain movement. For a single movement, a large number of such signals are combined with one another and merged into one directed movement.

In myasthenia gravis, the receptors on the muscle cells are partially or completely blocked or even destroyed. As a result, the muscle receives fewer or no signals from the brain at all. If there are fewer signals, only the precision and the power of the movements are reduced. If there are no more signals, the muscle is paralyzed. This severe form of myasthenia gravis is very rare.

The role of the thymus

Scientists suspect a connection between myasthenia gravis and pathological changes in the thymus. The thymus is an organ in which various cells of the immune system (also antibodies) are formed in childhood. Around 10 percent of all myasthenia gravis patients have a tumor in the thymus (thymoma), and around 70 percent of all patients have increased activity in the thymus (thymitis).

External factors influence the symptoms

It is assumed that fluctuations in the severity of symptoms are caused by external factors such as environmental influences, inflammation, emotional and psychological stress and other existing illnesses. However, this relationship has not been conclusively clarified.

Myasthenia gravis: examinations and diagnosis

In order to rule out other diseases and to be able to make a diagnosis as clearly as possible, various examination methods are used if myasthenia gravis is suspected.

The doctor suspects myasthenia gravis on the basis of the clinical picture during the physical examination and the recording of the medical history (anamnesis). Typical questions of the anamnesis can be:

• Where exactly do you feel the muscle weakness?
• How long have you been feeling these symptoms?
• When do these attacks of weakness occur, more often in the morning or in the evening or after you have exerted yourself?
• Do you also have problems chewing, swallowing or speaking?

Simple tests can confirm suspicions of myasthenia gravis, but they do not provide an accurate diagnosis.

The so-called Simpson test is carried out very often. Those affected have to look up as long as possible and open their eyelids wide. As a rule, the eyelids tire quickly, depending on the stage of the disease, opening the eyelids is no longer possible. After the administration of a certain medication (Tensilon) these symptoms disappear temporarily.

Another test method for suspected myasthenia gravis is electrical stimulation of individual nerves. The response of the muscles is recorded like an electrocardiogram (EKG). In the case of patients with myasthenia gravis, a characteristic drop, a so-called decrement, can be observed in the machine-generated curves, which, among other things, show muscle activity.

In addition to the neurological examination, a laboratory analysis is also useful if myasthenia gravis is suspected. The antibodies specific for the disease can be detected in a blood sample (acetylcholine receptor antibodies or anti-MuSK antibodies). Since a blood test is not always reliable, a laboratory test of muscle tissue is also carried out.

In addition, the function of the chewing and throat muscles can be assessed by experienced speech therapists and the degree of myasthenia gravis can be better assessed.

In order to determine the cause of myasthenia gravis or to research it in more detail, computed tomography (CT) is carried out in many cases, in which the thymus is examined more closely. Both an overproductive thymus and a tumor in the thymus could be seen on CT images.

Myasthenia gravis: treatment

Myasthenia gravis therapy is purely symptomatic, that is, it alleviates the symptoms, but cannot stop the course of the disease. A cure is not possible.

Myasthenia gravis: drug therapy

The symptoms of myasthenia gravis can be treated with medication. In most cases, the medication will need to be used for a lifetime. There are three different therapy options to choose from, which are used depending on the stage of myasthenia gravis:

1. Acetylcholinesterase inhibitors:

Acetylcholinesterase inhibitors improve signal transmission. This usually relieves the weakness of the muscles. It is often reported that the muscles of the extremities respond better to this therapy than the muscles of the face. Mostly the active ingredient pyridostigmine bromide is used, which can be taken orally. In severe cases or if intolerance has been proven, neostigmine or pyridostigmine are used, each of which is given directly into the vein (intravenous, i.v.).

2. Immunosuppressive treatment:

Glucocorticoids or azathioprine weaken the antibodies specific for myasthenia gravis and thus reduce the symptoms.

3. Plasmapheresis or high-dose immunoglobulin administration:

This therapy option is only used in the case of severe courses or if the breathing and throat muscles are impaired.

Myasthenia gravis: further therapeutic measures

Special swallowing therapy can be carried out with a trained speech therapist. In the case of moderate courses of myasthenia gravis, patients should, as a precaution, only consume food that is liquid and cannot be swallowed so easily. In severe cases, artificial feeding via a gastric tube as well as mechanical ventilation and regular suction of saliva may be necessary.

Double images can be balanced out well with an individually adapted prism glass.

In patients between 15 and 50 years of age, removal of the thymus is recommended as early as possible after diagnosis. In children up to 15 years of age, the thymus should only be removed if no improvement is achieved with drug therapy, since the thymus still fulfills important functions in childhood.

Myasthenia gravis: disease course and prognosis

It is not possible to give a general prognosis because every person affected with myasthenia gravis shows symptoms to different degrees, in different places and in different courses.

The majority of patients who are diagnosed and treated for myasthenia gravis respond well to therapy. Symptoms are alleviated and, in most cases, normal life can be resumed with only minor restrictions. In addition, the symptoms of myasthenia gravis are never continuous, so that those affected feel no impairment at all on some days and are subject to very severe restrictions on others.

If left untreated, symptoms of myasthenia gravis will continue to develop and serious complications can result. In extreme cases, when the respiratory muscles fail, it can be fatal. In other cases, lifelong mechanical ventilation is required. Since nowadays more attention is paid to myasthenia gravis and symptoms are often recognized early, such severe courses have become less common.

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