Myasthenia gravis in the elderly

Introduction to myasthenia gravis in the elderly Myastheniagravis (MG) is an autoimmune disease of neuromuscular synaptic transmission disorders. The main clinical feature is that the affected striated muscle is prone to fatigue, and the symptoms can be alleviated after rest or with anticholinergic drugs. Myasthenia gravis is a polygenic disease. It is currently believed that anti-acetylcholine receptor (AchR) antibody and antibody-mediated humoral immunity and T cell-mediated cellular immunity are the main pathogenesis. The thymus is the main factor that activates and maintains the autoimmune response of myasthenia gravis. Genetic and environmental factors are also closely related to the onset of myasthenia gravis. basic knowledge The proportion of illness: 0.001% Susceptible people: the elderly Mode of infection: non-infectious Complications: thymoma

The cause of myasthenia gravis in the elderly

(1) Causes of the disease

The etiology of myasthenia gravis (MG) is not well understood. Most studies have shown that MG is an autoimmune disease whose acetylcholine receptor antibody (AchRab) is abnormally elevated in patients and causes skeletal muscle end of life. Decreased number of acetylcholine receptors in the plate is associated with dysfunction, and family surveys and molecular biology studies suggest that the pathogenesis of MG may be related to heredity.

(two) pathogenesis

Most scholars believe that thymic lesions play a key role in the pathogenesis of MG. According to statistics, about 70% of MG patients have thymic hyperplasia, 10% to 15% of MG patients have thymoma, and about 5% of patients Thymus atrophy occurs in advance, observed under the microscope, thymic hyperplasia mainly manifests as lymphoid follicular hyperplasia, germinal center composed of B lymphocytes with dense clusters, and myoid cells, which have striations And acetylcholine receptors, presumably in some specific genetic trait individuals, due to infection of the thymus by viruses or other non-specific factors, resulting in changes in the conformation of acetylcholine receptors on muscle-like cells to express antigenic signals, stimulating the body to produce AchRab, and Causes immune damage to acetylcholine receptors on the skeletal muscle motor endplate.

In the above autoimmunity, the expression of autoantigen, the transmission of information between T and B lymphocytes, the production of autoantibodies and the immunological damage of the target tissue-acetylcholine receptor are all affected by human leukocyte antigen (HLA) DR, DP, DQ, etc. Regulation of the immune regulatory genes at the locus.

Elderly myasthenia gravis prevention

Important preventive measures are:

1 Avoid infection, trauma and overwork.

2 life rules, adequate sleep, exercise, quit smoking and alcohol.

3 cautious immunization (vaccination) injection.

4 Avoid the use of myasthenia gravis contraindications.

Elderly myasthenia complication Complications thymoma

Most cases are associated with thymic hyperplasia or thymoma, and a few cases are associated with autoimmune diseases such as hyperthyroidism.

Symptoms of myasthenia gravis in the elderly Common symptoms Myasthenia gravis limb weakness, muscle weakness, crisis, soreness, fatigue, pupil abnormalities, difficulty swallowing, difficulty breathing, dehydration

MG insidious onset, often in the fatigue, infection, trauma or trauma after the onset or aggravation, the symptoms of this disease are skeletal muscle weakness and abnormal fatigue, symptoms have volatility, morning light and heavy, increased after the event, relieve after rest, MG can be classified into the following three types depending on the clinical symptoms.

Extraocular muscle type

Extraocular muscle type MG is most common in the clinic. The first symptom is ptosis of the upper eyelid, often starting from one side, and then affecting the other side. There are also left and right upper eyelids that sag or alternately sag. When the eye movement is disordered, the patient may appear. Diplopia, because the pupil sphincter is not tired, there is no abnormal change of the pupil, and the extraocular muscle MG can be converted into other clinical types.

2. Medullary muscle type

The affected muscle group is the pharynx, laryngeal muscle or masticatory muscle. The patient is characterized by chewing weakness, difficulty in swallowing, drinking and coughing, hoarseness, coughing, and weakness.

3. Whole body type

The lesions involve the skeletal muscles of the whole body. In addition to the ptosis, diplopia, difficulty in swallowing, and hoarseness, the patient often has prominent limb weakness, but also has a head, a neck, and a shrug. The disease often affects the daily life and work of the patient. However, he was forced to stay in bed.

Some cases of MG can be naturally relieved, most cases are delayed for several years to several decades, and often the condition fluctuates.

Elderly myasthenia gravis

1. Serum lactate dehydrogenase, creatine kinase, cholinesterase and other activities are normal.

2. Serum anti-Ach receptor antibody is more than 80% positive, but antibody positive is not proportional to the severity of clinical symptoms.

3. Cerebrospinal fluid routine, biochemical indicators are normal, some patients can detect anti-Ach receptor antibodies.

4. Peripheral blood lymphocyte function test indicates that T cell function is declining, B cell antibody secretion capacity is hyperactive, but the number and proportion of T and B cells are normal.

5. More than half of the patients on the EEG showed mild diffuse waves and sharp waves.

6. EMG has a decreasing amplitude of muscle action potential (MAP) caused by low frequency repeated electrical stimulation (PNS), accounting for 41% to 95% of patients. Single fiber electromyography (SFEMG) is currently the most sensitive and accurate. The highest electrophysiological means, the positive rate can reach more than 90%. This technique uses a special single fiber electrode to measure the "jitter" to study the function of the nerve-muscle joint. Under normal circumstances, the "trembling" is 5 ~ 55s. If it exceeds 55s, it will be "trembling" widening. If 20 or more of the "trembling" recorded by one muscle is more than 55s, it is abnormal.

Diagnosis and diagnosis of myasthenia gravis in the elderly

Diagnostic criteria

1. MG diagnosis

(1) medical history: chronic onset or occult onset, local or systemic skeletal muscle weakness, symptom fluctuations, morning light and heavy, increased after activity, relieved after rest.

(2) Muscle fatigue test: According to the history of MG, the muscle fatigue test can be used to establish a clinical diagnosis. The commonly used muscle fatigue test is: 1 blink. 2 cough. 3 hands grasping action. 4 squatting up, generally according to the condition of the disease to choose 1 ~ 2 kinds of muscle fatigue test, sputum patients repeatedly do a certain action within 1min, such as 1min continuous blinking (blinking) 30 ~ 50 times, such as continuous blinking 30 ~ After 50 times, the ptosis was aggravated and the ocular fissure became small, which was positive for the muscle fatigue test.

(3) Neostigmine test: For patients with suspected MG, neostigmine can be injected intramuscularly with 0.5 to 1.5 mg. If the symptoms of myasthenia are significantly reduced or disappeared after 15 to 45 minutes, it is the neostigmine test. Positive, in order to antagonize the abdominal pain caused by neostigmine excitatory M receptor, bradycardia and other adverse reactions, can be an appropriate amount of atropine (0.25 ~ 0.75mg).

(4) Neurorepetitive electrical stimulation test: Repeated stimulation of the ulnar nerve, phrenic nerve or phrenic nerve with low-frequency direct current, MG patients can show typical action potential decline phenomenon, the decline is more than 10% is positive.

(5) AchRab titer determination: about 65% of extraocular muscle MG patients with elevated serum AchRab titer (or positive), 90% of systemic patients with increased AchRab titer, AchRab titer and clinical type of MG There is no correlation between the severity of the disease.

If there is skeletal muscle weakness and mild morning sputum, MG should be suspected; if the muscle fatigue test is positive, the MG can be diagnosed clinically; if the neostigmine test is positive or the nerve repeat electrical stimulation test is positive or the AchRab titer is higher than normal, The MG can be diagnosed clinically.

2. Diagnosis of MG crisis

(1) Myasthenia gravis crisis: mostly for newly diagnosed patients, accounting for more than 95% of myasthenia gravis crisis. Patients often suffer from generalized weakness after exertion of fatigue or upper respiratory tract infection, and difficulty breathing due to respiratory muscle weakness, coughing. Defecation is weak, severe cases of hypoxia, cyanosis, and even coma, death, neostigmine test positive.

(2) Cholinergic crisis: Most patients with MG who have been diagnosed with cholinesterase inhibitors have excessive or irregular medications. In addition to muscle weakness and difficulty in breathing, they often sweat, runny, dilated pupils, and bradycardia. Increased bronchial secretions and other similar organophosphate poisoning performance, neostigmine test negative, atropine test positive.

(3) rumination crisis: mostly for follow-up MG patients, often in surgery, trauma, dehydration, infection, neostigmine test negative, atropine test is also negative.

Differential diagnosis

Oculomotor paralysis

Common in cerebral aneurysms, midbrain lesions and diabetic patients, in addition to ptosis, limited eye movements, diplopia, often abnormal pupil changes, and no fluctuations in symptoms.

2. Medullary paralysis

The medullary myocardium MG needs to be differentiated from the true bulbar palsy caused by brain stem tumor or brainstem encephalitis and the pseudobulbaric palsy caused by bilateral pyramidal tract dysfunction. The true medullary palsy is repeatedly weakened or disappeared, false. Patients with bulbar palsy often have multiple strokes, with strong crying and strong laughter. Physical examination shows bilateral pyramidal tract signs.

3.Lambert-Eaton syndrome

The syndrome is mostly male. About 2/3 of the patients are associated with small cell lung cancer or intestinal adenocarcinoma. The muscle weakness is caused by limbs. After a little activity, the symptoms of muscle weakness can be alleviated. The neostigmine test is sometimes positive. The nerve low frequency electrical repeated stimulation test is often negative, the AchRab titer is normal, and it is effective with guanidine hydrochloride.

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