Why does the disease occur?
The prevalence of this pathology is 4 cases per 100 thousand population. It is noteworthy that at a young age, the disease most often affects women and adolescent girls, in old age both men and women fall ill with a gender frequency of 1: 1.
The reason for the development of myasthenia gravis is not yet fully understood. Today, the following factors can provoke the development of the disease:
- Pathology of the thymus gland or thymus, as well as other glands (adrenal glands, pituitary, thyroid).
- Mutations in the genes encoding the work of neuromuscular synapses.
- Exogenous causes (hypothermia, frequent stress, physical stress, infections, autoimmune diseases).
More than 60% of patients with myasthenia revealed a pathology of the thymus (thymus gland) – hyperplasia or thymoma.
The main symptoms of the disease arise from the fact that the receptors of the striated muscles no longer bind to acetylcholine, a mediator produced by nerve endings. The receptor does not receive “fuel”, because of which muscular activity is absent.
This is due to:
- development of own antibodies to acetylcholine receptors;
- insufficient production of acetylcholine;
- excessive activity of the enzyme acetylcholinesterase, which destroys the mediator.
Thymus hyperplasia causes an excessive secretion of thymine hormone in the blood, which triggers a cascade of autoimmune reactions leading to the destruction of muscle receptors due to increased production of cholinesterase and antibodies.
The mechanism of development of the disease occurs at the level of the neuromuscular synapse: the impulse that travels from the neuron to the myocyte is blocked — muscle contraction does not occur. The muscles of the eyelids, torso and extremities, and the masticatory muscles are affected most often.
The first symptoms of myasthenia are associated with selective dysfunction of certain muscle groups. Often the disease debuts with damage to the muscles of the eyes – ophthalmic syndrome: by the end of the working day, the patient may experience temporary doubling in the eyes (diplopia), the omission of the upper eyelid (ptosis), difficulty in rotating the eyeballs.
If muscle changes do not spread beyond the eye area, this form of the disease is called ocular myasthenia. If muscular weakness progresses, other muscle groups are also involved in the pathological process – mimic, swallowing, neck, trunk and extremity muscles, a generalized form of myasthenia develops.
There are 4 forms of myasthenia, which are characterized by a specific clinical picture:
- Generalized – increased fatigue and weakness up to paresis or paralysis develops in almost all muscle groups. If the disease develops gradually, then at its beginning, patients may complain of double vision or ptosis by the end of the day after the visual load. In addition to visual disorders, swallowing and speech can be disturbed, weakness in the limbs develops, leading to paresis or paralysis, neck muscles suffer, which makes it difficult for the diseased to hold the head. The most severe symptoms of this disease are suffocation due to weakness of the respiratory muscles, and cardiac disorders.
- Bulbar – a form of myasthenia gravis, characterized by pathological changes in the centers of the brain stem, accompanied by impaired speech, swallowing, chewing.
- Ocular – in this pathology, the muscles of the eye are isolated in isolation: patients complain of double vision, overhang of the upper eyelid, and squint. The functions of the muscles of the torso, pharynx, limbs are not violated.
- Body – manifestations of this form include damage to the muscles of the limbs, abdomen, chest.
According to its course the disease is:
- Malignant – from the onset of symptoms to severe breathing disorders, swallowing takes about two weeks.
- Progressive – the disease develops gradually, slowly, but its symptoms are steadily progressing, and the patient’s condition worsens.
- Stationary (non-progressive) – for a long time the patient’s condition remains stable, without negative or positive dynamics of the muscular pathology.
- Episodic – muscle disorders are temporary, transient. They can occur when the immunity is weakened, against the background of stress, transferred infection, intoxication. After stabilization of the patient’s general condition, the symptoms of the disease may disappear without a trace.
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The quintessence of the clinic of the disease are myasthenic crises – a sharp deterioration in the condition of patients in which the symptoms of the disease increase sharply. Crises can be triggered by a lack of therapy, a change in the dosage of the drugs taken, an infection, physical or psycho-emotional stress.
More often crises occur in patients suffering from generalized or bulbar myasthenia gravis. The onset of a crisis is indicated by a sharp increase in muscle weakness, the appearance or aggravation of respiratory disorders, a violation of swallowing movements, aphonia. Patients are scared and anxious because of a sharp deterioration in their well-being.
Without emergency medical care, the consciousness of patients can change: become soporous or comatose, there are cardiac disorders (tachycardia, a drop in blood pressure, life-threatening arrhythmias).
How to diagnose a disease?
Diagnosis of myasthenia gravis is based on the clinical picture, as well as laboratory and instrumental methods of research, specific samples.
Important diagnostic value have:
- Prozerin sample – the patient is injected under the skin 1-3 ml of a 0.05% solution of prozerin. If myasthenia gravis is present, then after the injection, its symptoms diminish by 2-3 hours: physical activity improves for a while.
- Test with the opening of the eyes, protruding the tongue – the patient for 40 times alternately opens and closes the eyes or 40 times sticks out the tongue. A positive test result confirming the diagnosis is observed if, after these exercises, ptosis appears, speech disorders occur, and the language is limited.
- Electromyography is a highly informative instrumental method of research, allowing to explore the potentials of individual muscle fibers. With myasthenia, a temporary decrease in the amplitude of the muscle response is observed.
- Pneumomediastinography – allows you to identify changes in the thymus in most patients.
- Serological examination of the blood – in 90% of patients with a generalized form and in 70% with ocular syndrome, antibodies to the cholinergic receptors of the postsynaptic membrane are detected.
For accurate diagnosis, in addition to clinical symptoms, the doctor must have at least 2-3 confirmatory diagnostic tests with a positive result, as well as the conclusion of a serological blood test.
Treatment of myasthenia
Treatment and prognosis of myasthenia in each case is individual and depends on the form of the disease, the nature of its course. Therapy requires an individual approach: the doctor must take into account the characteristics of the particular patient, the stage of the disease, and the accompanying pathology.
Today, the treatment of the disease can be carried out conservatively (with the help of drugs) and surgically.
Anticholinesterase agents demonstrate a good therapeutic effect in the treatment. Clinical studies have shown that in patients with local forms of myasthenia, the use of this group of drugs can stabilize the course of the disease.
The anticholinesterase inhibitors include:
- Prozerin 15 mg orally or 0.05% solution, 2-3 ml subcutaneously.
- Kalimin 30-60 mg 3-6 times a day.
The preparations of this group contribute to the accumulation of acetylcholine in the synaptic cleft due to the inhibition of its destruction.
In the treatment of myasthenia, other pharmacological groups of drugs are also used:
- Hormonal drugs: Prednisolone courses in high doses for 1-2 weeks, and then a gradual transition to a dose of 5-15 mg daily or 10-30 mg every other day.
- Cytostatics: Azathioprine 50-150 mg per day, Cyclosporine up to 5 mg / kg per day.
- Immunoglobulins in / in the rate of 0.4g / kg / day for 5 days.
- Anabolic steroids (can be prescribed to men): Retabolil 1-2 injections per week, and then 1 injection every 3-4 weeks.
The treatment regimen prescribed by the doctor cannot be adjusted or canceled. Drugs need to be taken only in the dosage recommended by a specialist.
Treatment with folk remedies does not have the desired effect in the treatment of the disease and may cause more harm than good.
In case of failure of conservative treatment, with a steady progression of the disease, the presence of a generalized form of the disease in patients under the age of 70 years, as well as in the diagnosis of thymoma, removal of the thymus gland may be recommended.
A good prognosis for operative intervention is in young patients with a disease duration of up to five years: in 80% of the operated patients there is an improvement in condition and a stable remission (five years or more). In many patients after radical surgery, it turns out to completely get away from the medication of anticholinesterase drugs or significantly reduce their dosage.
Contraindications to surgery are decompensated somatic diseases, an unresectable malignant tumor with multiple metastases to other organs, age over 70 years. Often, with the ocular form of myasthenia, surgical treatment is ineffective.
If the operation is performed for a thymus tumor, then before and after surgery the patient is undergoing radiation therapy.
Myasthenic Crisis Therapy
With the development of the crisis of the disease, patients should be provided with qualified medical assistance in inpatient conditions, and if there is respiratory depression, then in the intensive care unit.
In case of any violations of the respiratory system or in the event of dysphagia, the patient should be transferred to artificial respiration in order to avoid paralysis of the respiratory muscles. The frequency of breathing, heart rate, blood oxygen saturation is monitored around the clock.
Patients with myasthenic crises are given pulse therapy with glucocorticosteroids and high doses of anticholinesterase drugs are prescribed until they feel better. After the relief of an acute condition, the basic treatment regimen is adjusted, avoiding high doses of drugs.
Patients should be trained to recognize the “precursors” of crises: time to notice an increase in weakness, the appearance of speech disorders, difficulty swallowing and other specific symptoms indicating a possible exacerbation of the pathological process, and in time to seek medical help.
Today, with successful treatment, the prognosis, even with severe forms of myasthenia, has become many times more favorable.
Patients with non-progressive, episodic, ocular form with maintenance therapy lead a full-fledged lifestyle and live to old age.
Less favorable prognosis in the presence of a thymus tumor, with the disease with frequent crises in history. Crisis can lead to the development of acute respiratory failure and cause death.
The following sources were used to prepare the article:
1. Bykov Yu. N. Smolin A. I. Treatment and rehabilitation of patients with myasthenia // Siberian Medical Journal – 2013 – №4
2. Konkova D. Yu. The history of the study of myasthenia – from describing the symptoms to studying the pathogenesis // Far Eastern Medical Journal – 2015
3. Skvortsov M. B. Smolin A. I. Myasthenia. Surgical treatment and its effectiveness // Acta Biomedica Scientifica – 2012 – №4 (86)