Myasthenia gravis, or MG for short.
The main clinical feature is that the local or generalized muscles are easily fatigued and weak during activities, which can be relieved by rest or anti-cholinesterase drugs. The main cause of MG is an immune disorder that generates autoantibodies that prevent acetylcholine at the neuromuscular junction from binding to the receptor (AChR) and causing normal muscle contraction. The source of the antibody production is in the thymus gland and its surrounding adipose tissue.
How to know if you have myasthenia gravis
The disease is seen at any age and has a low incidence of 0.5 to 1 per 100,000, but there are two peak periods: one is between 20 and 30 years old, more common in women and often associated with thymic hyperplasia; the other is between 40 and 50 years old, more common in men and associated with thymoma and other diseases, such as hyperthyroidism and rheumatoid arthritis. The main symptoms are skeletal muscle fatigue after a little activity and improvement after a short rest. The most common symptom is extraocular muscle as the first symptom, followed by medullary muscle and limb band muscle, and the most serious one is the weakness of respiratory muscle. The involvement of extraocular muscles manifests as drooping eyelids, diplopia and strabismus; the involvement of medullary muscles manifests in masticatory muscles and pharyngeal muscles with difficulty in chewing, eating and swallowing, choking and coughing when drinking, and slurred speech; the involvement of facial muscles manifests in lack of expression and weakness in closing the eyes; the involvement of limb muscles manifests in proximal weakness, easy to fall when walking, and difficulty in going upstairs; if the respiratory muscles are invaded, there is difficulty in breathing, which is called myasthenia gravis crisis. Most of the disease starts insidiously, often starting with one group of muscles and gradually involving other groups, and a few patients develop muscle atrophy. The above symptoms often fluctuate, showing the clinical characteristics of “lighter in the morning and heavier in the evening”, aggravated by repeated activities and relieved by rest. Flu, emotional stress, exertion, menstrual flow, use of narcotic sedative drugs, childbirth, surgery, etc. often cause the disease to recur or worsen. Almost all children with myasthenia gravis have eye muscle involvement, which is characterized by drooping eyelids, diplopia and even eye fixation, with symptoms alternating between good and bad or left and right. If the above symptoms are found, there is no difficulty in diagnosis, and the diagnosis should be confirmed by a doctor in time.
What are the dangers of myasthenia gravis?
Myasthenia gravis is a chronic disease that seriously affects work and life and is difficult to cure on its own. In mild cases, the eyelids droop and the vision is blurred, while in severe cases, it is difficult to eat, walk or even breathe. The most dangerous complication of myasthenia gravis is myasthenic crisis. When the condition suddenly worsens or is not treated properly, causing respiratory muscle weakness or paralysis and resulting in severe respiratory distress, it is called myasthenia gravis. There are three types of myasthenic crisis: 1) myasthenic crisis 2) cholinergic crisis 3) reflexive crisis. Severe crisis can lead to sudden respiratory arrest and death. Therefore, it is important to go to the hospital immediately for thorough examination when the above conditions are found.
How to confirm the diagnosis of myasthenia gravis
Due to the lack of medical knowledge, people with eyelid weakness often go to the ophthalmology department first. In the past, when medical technology was relatively backward, there were cases where the eyelid was misdiagnosed as an overgrown eyelid and the eyelid was removed, but the eye could no longer be closed. It is recommended that patients who have never had an eye problem before and suddenly develop these symptoms should first visit a general hospital thoracic surgery or neurology department to prevent misdiagnosis and omission. The diagnosis of this disease is not difficult based on clinical features: muscle fatigue test, such as repeatedly opening and closing eyes, clenching fists, holding both upper limbs flat or squatting continuously, can make muscle weakness more obvious and help to diagnose. To confirm the diagnosis, the following auxiliary tests can be further performed.
I. Drug test.
(1) Neostigmine test. ②Tensilon chloride test. The rapid improvement of muscle weakness after drug injection is considered positive, easy to perform and has the greatest confirmatory value, which can also be done in primary hospitals.
II. Electrophysiological examination.
Commonly used electromyography examination, divided into low-frequency stimulation and high-frequency stimulation, with the former results more reliable. This test has important value for the typing and differential diagnosis of myasthenia gravis.
Third, other: anti-AchR antibody measurement in serum is increased in about 85% of patients. Chest X-ray or CT examination, which reveals thymic hyperplasia or concomitant thymic tumor, also has auxiliary diagnostic value. In elderly male patients concomitant malignant tumors should be excluded at the same time to avoid delaying the treatment of the primary disease.
How to treat myasthenia gravis
I. Drug treatment.
(1) Anticholinesterase drugs: such as oral pyridostigmine, neostigmine bromide. This treatment is like treating diabetes with insulin, which is alternative treatment rather than real etiological treatment. Therefore, in principle, it is only used for patients with mild disease such as simple ocular muscle type.
(2) Polarizing solution plus neostigmine 0.5-2.0mg and dexamethasone 5-15mg IV once/day, 10-12 times as a course of treatment.
II. Immunosuppressants.
(1) corticosteroids: prednisone 60-7Omg orally daily or every other day, and can be reduced to the smallest effective dose after symptom relief. Side effects are obesity, hypertension, diabetes mellitus and secondary cardiovascular disease.
(2) Immunosuppressants: cyclophosphamide 200mg/day, divided into 2-3 oral doses; or azathioprine 50-150mg/day, divided into 2-3 oral doses. However, long-term use does not exclude the possibility of carcinogenesis.
(3) Gammaglobulin: It is a blood product, and its repeated use increases the risk of blood-borne diseases.
(3) Blood therapy: plasma replacement therapy can be used when available. The disadvantage is that a large amount of allogeneic plasma needs to be imported, and there is a possibility of infection with blood-borne diseases, and it often needs to be repeated several times, which is expensive. Therefore, it is mainly used in severe critical cases or as a preparation before surgery.
IV. Surgical treatment.
The surgical treatment of myasthenia gravis is a legendary page in medical history and a successful example of clinical experience guiding theoretical research. in 1936 Dr. Blalock performed thyroidectomy on a 19-year-old female patient with myasthenia gravis, and the miraculous relief of myasthenia gravis symptoms after surgery brought his attention to the potential relationship between the thymus gland and this disease. in 1944 he consciously applied thyroidectomy In 1944, he consciously and creatively applied thymectomy to patients without thymoma, which achieved great success and opened a new chapter in the surgical treatment of myasthenia gravis, which also triggered a wave of research on this autoimmune disease. With recent improvements in anesthesia techniques, surgical approaches and respiratory management, thymectomy has become safer, with highly satisfactory results both in the near and long term, and surgery has been adopted as the treatment of choice for myasthenia gravis in developed countries.
So, what conditions are suitable for surgical treatment? Currently, the more recognized indications for surgery include.
1, all cases of thymoma or non-thymoma, but the disease is progressing rapidly, anti-cholinesterase drug treatment response is not satisfactory, regardless of whether the anti-AChR antibody is increased, can be thymectomy. The American Academy of Neurology Quality Standards Committee evaluated the effectiveness of thymectomy and concluded that early thymectomy is more valuable than late thymectomy in the natural course of the development of myasthenia gravis.
2.Female patients between 30-40 years of age, patients with generalized myasthenia gravis with a short course and mild disease with thymic hyperplasia.
3, simple eye muscle type myasthenia gravis simple eye muscle type myasthenia gravis surgery is safe and effective, and can prevent its transformation into a generalized type. At present, most experts advocate that regardless of the clinical classification of myasthenia gravis, surgery is required once the diagnosis is clear, because even for the so-called “simple” ocular muscle type patients, most of them (86%) will develop into the generalized type within a year. However, in the case of preschool children, due to the concern of the effect on the function of the thymus gland, it is still recommended to use pharmacological treatment first.
4. Patients with myasthenia gravis should not receive immediate surgical treatment, but should first receive medication, and then surgery after the symptoms are controlled can reduce the occurrence of postoperative crisis.
Minimally invasive thymectomy
Although surgical removal of thymus and anterior mediastinal fat tissue is a reliable method to cure myasthenia gravis, with obvious advantages of good long-term effect and high cure rate, the traditional surgical method pioneered by Dr. Blalock requires sawing through the sternum, which is traumatic, painful and leaves unsightly longitudinal scars of more than 20 cm in the anterior chest, which is the biggest obstacle for many patients, especially young women, who are afraid to accept surgery. This is the biggest obstacle for many patients, especially young women, who hesitate to undergo surgery. In fact, young female patients should receive surgery as early as possible because studies have shown that 86% of patients eventually develop the generalized type, and surgery is most effective within one year of onset.
Given this paradox and embarrassment in treatment, is there a new way to accomplish the same quality of surgery with minimal incisions? We should be grateful for the advent of television thoracoscopy, a micro-innovation technology originating from the United States more than 10 years ago, which allows most patients to complete the surgery through three small, concealed incisions, 1 to 2 cm long, under one axilla. Since the first thoracoscopic thymectomy appeared in 1993, tens of thousands of surgical procedures have been accumulated internationally. With the gradual improvement of the surgical technique, more and more reports support this new procedure. There is now an academic consensus that thoracoscopic surgery has achieved the same results as traditional sternotomy with significantly less trauma and more concealed and beautiful incisions. Women who love beauty can boldly walk on the beach in a bikini after surgery and will no longer have a psychological shadow.
In China, the first thoracoscopic minimally invasive thymectomy was reported in 1994. It has now been promoted as a mature surgical technique, bringing benefits to the majority of patients with severe myasthenia gravis.