What is Myasthenia Gravis?

Myasthenia gravis (MG) is an autoimmune disease caused by transmission dysfunction at the nerve-muscle junction. The clinical manifestations are partial or systemic skeletal muscle weakness and fatigue, symptoms worsen after activity, and symptoms decrease after rest. . The prevalence rate is 77 to 1.5 million, and the annual incidence is 4 to 11 million. The prevalence of females is greater than that of males, about 3: 2, and they occur at all ages, with children mostly 1-5 years old.

Basic Information

nickname: Myasthenia gravis
English name: myasthenia gravis
Visiting department: Neurology
Multiple groups: female

Common causes: Mostly related to autoimmune diseases, infections, drugs, and environmental factors
Common symptoms: Drooping eyelids, blurred vision, diplopia, strabismus, bitter smile, etc.
Contagious: no

Causes of myasthenia gravis

The causes of myasthenia gravis are divided into two major categories. One is congenital, rare, and has nothing to do with autoimmunity. The second is autoimmune disease, which is the most common. The cause of the disease is not clear, and it is generally believed to be related to infection, drugs, and environmental factors. At the same time, 65% to 80% of patients with myasthenia gravis have thymic hyperplasia, and 10% to 20% are associated with thymoma.

Clinical manifestations of myasthenia gravis

Patients with myasthenia gravis often feel the eyes or limbs sore and uncomfortable at the beginning of the onset, or the vision is blurred, easily fatigued, and the fatigue becomes worse when the weather is hot or menstrual cramps. With the development of the disease, the skeletal muscles are obviously fatigued and weak. The significant feature is that the muscle weakness is aggravated in the afternoon or evening after fatigue, and it is relieved in the morning or after rest. This phenomenon is called "morning light and twilight."

1. Patients with myasthenia gravis can be affected by skeletal muscles, and may have the following symptoms

(1) Droopy eyelids, blurred vision, diplopia, strabismus, and inflexible eyeball rotation.

(2) Indifferent expression, bitter smile, big tongue, difficulty in articulation, often accompanied by nasal sounds.

(3) weak chewing, coughing with drinking water, difficulty swallowing.

(4) The neck is soft and the head is difficult to lift.

(5) Difficulty raising arms, combing hair, going up stairs, squatting, getting in the car.

2. Clinical typing

(1) Improved Osseman typing method type I ophthalmic muscle type; type IIA mild systemic type, muscles of the limbs are often associated with eye muscles, and there is no pseudoball paralysis, that is, there is no articulation due to chewing and swallowing difficulties. Type IIB limb muscle group is often accompanied by eye muscle involvement, showing the appearance of pseudobulbar paralysis, and most of the breathing difficulties occurred within six months. Type III (severely aggressive) has a rapid onset and develops from several weeks or months to dyspnea. Type IV (late-onset severe type) evolved from type I, type IIA, and type IIB in about 2 years. V-type muscular atrophy is rare.

(2) Myasthenia crisis refers to the severe deterioration of myasthenia gravis due to some reason during the course of the disease, breathing difficulties, and life-threatening critical phenomena. According to different reasons, MG crisis is usually divided into 3 types: Muscle weakness crisis is mostly due to the development of the disease itself. It can also be caused by infection, excessive fatigue, mental stimulation, menstruation, childbirth, surgery, trauma. The clinical manifestations are that the patient's muscle weakness symptoms suddenly worsen, weakness in swallowing and sputum, difficulty breathing, often accompanied by restlessness, sweating and other symptoms. Cholinergic crisis is seen in patients who take large doses of "bromopyramine" for a long time, or overdose for a while, and often shows nausea, vomiting, abdominal pain, diarrhea, sweating, tearing, Damp cold skin, increased oral secretions, tremor of muscle bundles, and emotional symptoms such as emotional agitation and anxiety. The dose of the anti-crisis crisis "bropiramine" did not change, but suddenly the drug failed and severe breathing difficulties appeared. It can also be caused by infection, electrolyte disturbances, or other unknown causes.
Myasthenia gravis crisis is the most common among the above 3 kinds of crisis, followed by antirecurrent crisis. Real cholinergic crisis is very rare.

Myasthenia gravis

Neostigmine test

Adults generally use intramuscular injection of 1 to 1.5 mg of neostigmine. If the symptoms improve 10 to 15 minutes after injection, a peak is reached in 30 to 60 minutes and lasts 2-3 hours.

2. Thymus CT and MRI

Thymic hyperplasia or thymoma can be found, and if necessary, intensive scanning should be performed for further clarification.

3. Repeated electrical stimulation

Repetitive electrical nerve stimulation is a commonly used diagnostic method with diagnostic value. The electrodes are used to stimulate the motor nerves and record the amplitude of the reflected potential of the muscles. If the patient's muscle potential gradually declines, it indicates the possibility of a lesion at the neuromuscular junction.

4.Single fiber EMG

Single-fiber electromyography is a more sensitive method for detecting abnormal conduction in neuromuscular junctions than repeated electrical nerve stimulation. The abnormal neuromuscular conduction can be found based on the increase in "trembling" when the repeated electrical stimulation and clinical symptoms are normal. Of all the muscle weakness tests, the sensitivity is the highest.

5. Detection of acetylcholine receptor antibody titer

The detection of acetylcholine receptor antibody titer has characteristic significance for the diagnosis of myasthenia gravis. Serum acetylcholine receptor antibodies can be detected in 80% to 90% of the systemic and 60% of the ocular myasthenia gravis. The level of antibody titers is not exactly consistent with the severity of clinical symptoms.

Myasthenia gravis treatment

Drug treatment

(1) Cholinesterase inhibitors are symptomatic drugs. They do not treat the symptoms and do not cure the symptoms. They cannot be used for a long time as a single drug. The method of use should be gradually increased from a small dose. Commonly used are neostigmine methyl sulfate and brompisamine.

(2) Immunosuppressants The commonly used immunosuppressants are: adrenal corticosteroids: prednisone, methylprednisolone, etc .; azathioprine; cyclosporin A; cyclophosphamide; tacrolimus Division.

(3) Plasma replacement By removing the acetylcholine receptor antibody from the patient's blood, the symptoms of patients with myasthenia gravis are temporarily relieved. The effect is not more than 2 months if it is not supplemented with other treatments.

(4) Intravenous injection of immunoglobulins Human immunoglobulins contain a variety of antibodies that can neutralize autoantibodies and regulate immune functions. The effect is comparable to that of plasma exchange.

(5) Chinese medicine treatment Chinese medicine treatment of myasthenia gravis is getting more and more attention. Myasthenia gravis belongs to the category of "hysteria". According to the theory of traditional Chinese medicine, the addition of traditional Chinese medicine to the treatment can reduce the side effects of immunosuppressive agents, play a escort role in the treatment of myasthenia gravis, and can rebuild the function of autoimmune function.

2. Thymectomy

More than 90% of patients have abnormal thymus. Thymectomy is one of the effective treatments for myasthenia gravis. It is applicable to patients with myasthenia gravis who are systemic and have no contraindications to surgery between the ages of 16 and 60. Most patients can significantly improve after thymectomy. 10% to 15% of patients with thymoma are absolute indications for thymectomy.

Myasthenia gravis prognosis

Patients with myasthenia gravis have a better prognosis. A small number of patients can be completely relieved after treatment. Most patients can be maintained with drugs to improve their symptoms. The vast majority of patients with good curative effects can carry out normal study, work and life.

Myasthenia gravis prevention

1. Factors that may make myasthenia gravis worsen or relapse

Common causes are infection, surgery, trauma, systemic disease, excessive fatigue, women's physiological period, pregnancy, childbirth, smoking, drinking, and recurrence of thymoma.

2. Drugs for patients with myasthenia gravis

(1) antibiotics gentamicin, streptomycin, kanamycin, tetracycline, oxytetracycline, bacteriophthalein, polymyxin, tobramycin, quinolones, and macrolides should be used with caution

(2) Use lipid-lowering drugs with caution.

(3) Phinegan, diazepam, diazepam, morphine, ether, anesthetic muscle relaxant, procaine, aminoglycosides.

(4) Quinine, quinidine, procainamide, hibernation, perphenazine.

(5) Arrow poison, succinylcholine.

(6) Thymosin, carzenzol, Bingningketong, immune enhancers.

(7) Toad crisps and proprietary Chinese medicines, such as: Liushen Pill, throat disease, etc., pearl powder.

(8) Do not casually give children with myasthenia gravis a variety of commercially available oral solutions that claim to have an immune-enhancing effect.