myasthenia

Myasthenia gravis - an autoimmune disease that causes violation of neuromuscular transmission and shows weakness and abnormal fatigue of skeletal (striated) muscle. The disease is associated with the formation of antibodies against acetylcholine receptors located on the postsynaptic membrane of the neuromuscular synapse. Neonatal myasthenia - transient state, observed in infants born to mothers suffering from myasthenia gravis, and due to the passage through the placenta of maternal antibodies to acetylcholine receptors.

Myasthenia gravis can occur at any age, but the peak incidence occurs in the 20-40 and 65 - 75 years. In most cases, the disease primarily involves the eye muscles, so the first patients complain of double vision and drooping century. Over the next 1-2 years, the majority of patients there is a generalization process with the addition of facial weakness and bulbar muscles, muscles of the neck, trunk and extremities. However, in some patients the disease does not spread further outside the eye muscles (eye shape). Characterized by marked fluctuations of symptoms during the day, in connection with this disease are often mistaken for hysteria. The phenomenon of abnormal increase of muscle fatigue manifests symptoms on a background of physical activity (eg, increased dysphagia during the meal, and dysphonia - during a conversation). Characteristically the absence of autonomic disorders (disorders of innervation of the pupil or pelvic disorders), sensitivity disorders. Neurological examination revealed decrease in strength, increasing the repetition of movements. To enhance ptosis patient is offered to fix the eye by pushing up or asked to raise their hands up to 30 - 60 seconds. To identify weaknesses patient laryngeal muscles are asked to count out loud to 100. Reflexes are usually normal. Often there is selective muscle involvement (eg, neck flexors are weaker than the extensors), it allows to distinguish from asthenia gravis or hysteria. The symptoms of myasthenia may exacerbate a number of drugs that can be administered to the patient only when strictly necessary, provided a stable state. This group consists of antibiotics (streptomycin, gentamycin and other aminoglycosides, polymyxin B, colistin, tetracycline, ampicillin, erythromycin, ciprofloxacin, clindamycin), sulfonamides, cardiovascular (beta-blockers, quinidine, lidocaine, procainamide, calcium antagonists), antiepileptics (Trimethadione, phenytoin, carbamazepine, barbiturates), and lithium preparations chlorpromazine, diazepam (relanium) mioplegicheskie agents, quinine, corticosteroids, thyroid hormone, magnesium salts, iodine containing radiopaque material.

In patients with generalized myasthenia sometimes a rapid deterioration with the development of respiratory failure associated with weakness of the respiratory muscles and the bulbar muscles (myasthenic crisis). The crisis may occur with infection or taking drugs that violate the neuromuscular transmission. The development of a crisis may be preceded by marked fluctuations in muscle weakness, decreased body Mars, the restriction of motor activity, increased head droop, increasing dysarthria, dyspnoea . Less increase in muscle weakness and respiratory failure can be caused by an overdose of anticholinergic agents (cholinergic crisis). In favor of this option suggests a crisis generalized fasciculations and cramps, salivation, increased peristalsis, diarrhea, vomiting , bradycardia .

Diagnosis. To confirm the diagnosis is performed prozerinovuyu sample with 2 ml of 0.5% solution of neostigmine, which is administered subcutaneously and observed for the effect for 40 minutes. The sample should be performed only when the detected specific muscle weakness. To eliminate the placebo effect, previously recommended to enter the saline. To correct the possible side effects of neostigmine (bradycardia, bronchospasm, hypotension) should also have ready a syringe with 0.5-1 mg atropine and Ambu bag. With the introduction of neostigmine may be other unwanted effects - hypersalivation, lacrimation, fasciculations, diarrhea, intestinal colic , nausea , incontinence of urine and feces. Diagnosis is also confirmed by the definition of antibodies to acetylcholine receptors. In adults with a confirmed diagnosis of myasthenia shows pnevmomediastinografiya or CT scan of the chest to exclude thymoma. To exclude hyperthyroidism, often combined with myasthenia gravis, examine the contents of thyroid hormones or conduct other tests that determine the functional activity of the gland. To exclude other autoimmune diseases research shows rheumatoid factor, antinuclear antibodies.

Treatment. Anticholinesterase agents inhibit the breakdown of acetylcholine in the synapse, and increase muscle strength. Most used pyridostigmine (kalimin). When administered starts its operation after 10 - 30 minutes, reaching a peak after two hours and then for 2 hours, gradually weakens. Treatment starts with 30 mg 3 times a day, then increase the dose to 60-120 mg every 4 to 6 hours. Although pyridostigmine is effective in most patients, but only a small proportion of these symptoms regress completely. Common side effects - abdominal pain, nausea , diarrhea, hypersalivation. The drug is contraindicated in chronic obstructive pulmonary disease and asthma. Corticosteroids are prescribed for lack of efficacy of anticholinesterase agents. They cause an improvement in 70 - 90% of patients, but the first 3 weeks, especially when treatment is initiated with a high dose, muscle weakness (including respiratory and bulbar) may grow. After reaching a stable effect begin to slowly reduce the dose. In a large proportion of cases, patients are forced to take a maintenance dose of the drug for many years.

Immunosuppressants (azathioprine, cyclosporine, and cyclophosphamide less) prescribed for generalized or tabloid form by poor tolerability of corticosteroids. Thymectomy is indicated in younger patients (under 60 years) with generalized form of the disease, and in patients with thymoma. If signs of myasthenic crisis the patient must be urgently hospitalized in the intensive care unit. It is advisable to put the patient in a semi-sitting position, give oxygen through a mask or nasal catheter. Enter intravenously 1 ml of 0.05% solution of neostigmine and begin a slow intravenous infusion of neostigmine (per day enter 8-12 mg). If the infusion is temporarily unavailable, the drug can also be administered intramuscularly at a dose of 1.2 mg). To avoid side effects simultaneously administered atropine (0.5 mg subcutaneously 3 - 5 times a day). Assign corticosteroids (100 mg / day), but they may temporarily strengthen weakness; plasmapheresis is performed. It is important to monitor the airway and lung capacity. With the development of respiratory failure is carried out intubation and start ventilation. If signs of infection prescribe antibiotics (preferably cyclosporins). In cholinergic crisis anticholinesterase drugs temporarily canceled, reduced airway, subcutaneous atropine (0.5-1 mg every 2 hours) until dry mouth, prescribe cholinesterase reagent-tori (Dipiroksim 150-300 mg intravenously or intramuscularly) if necessary resorting to intubation and mechanical ventilation.