Myasthenia gravis is an autoimmune disease with impaired transmission at the neuromuscular junction. The main clinical feature is localized or generalized fatigue and weakness of the transverse muscles during activity. The disease is mainly caused by the decrease of acetylcholine receptors (AChR) in the postsynaptic membrane. Duan Ruisheng, Department of Neurology, Shandong Qianfo Mountain Hospital
This disease is seen at any age. It may be associated with thymoma in 15-20% of cases, and thymic hyperplasia in 70%. The main symptom is skeletal muscle fatigue after a little activity, which improves after a short rest. The symptoms are usually mild in the morning and severe at night, but can be variable. Cold, emotional stress, overexertion, menstruation, use of anesthesia, sedative drugs, childbirth, surgery, etc. often cause the disease to recur or worsen. The muscles innervated by the cranial nerves, especially the extraocular muscles, are most likely to be involved and are often the only symptom; in mild cases, the eye movements are involved, with asymmetric eyelid ptosis, weakness in eye opening, strabismus, diplopia, and sometimes alternating bilateral eyelid ptosis; in severe cases, both eyeballs are immobilized, and eye muscle involvement is more common in children under 10 years of age. Children under 10 years of age may also have difficulty chewing and swallowing, hoarseness, choking and coughing, and difficulty lifting the head. In severe cases, limb weakness may develop. If respiratory muscle weakness or paralysis occurs, resulting in severe respiratory distress, it is called myasthenia gravis crisis.
The diagnosis is not difficult based on clinical features. The muscle fatigue test (e.g. repeated opening and closing of eyes, clenching of fists or holding both upper limbs flat can make muscle weakness more obvious), neostigmine test, repetitive electrical nerve stimulation, anti-AChR antibody test and CT examination of the thymus can help in the diagnosis.
Treatment of the disease should be individualized and includes: 1. pharmacological treatment, such as anticholinesterase drugs (oral pyridostigmine, neostigmine bromide), corticosteroids (methylprednisolone, prednisone), immunosuppressants (azathioprine, cyclophosphamide) and intravenous immunoglobulins. 2. thymectomy. 3. 2. thymectomy. 3. plasma replacement therapy. 4. herbal medicine.