Myasthenia Gravis - Questions and Answers Print E-mail

What is myasthenia gravis?
Answer: Myasthenia gravis is an acquired autoimmune disorder of neuromuscular transmission.

Question: What is the cause of myasthenia gravis?
Answer: It is due to autoimmune destruction of the post synoptic membrane of the neuromuscular junction caused by circulating antibodies to the acetylcholine receptors.

Question: What are cardinal clinical features of myasthenia gravis?
Answer: The disease is characterized by fluctuating weakness, mainly involving the ocular and bulbar muscles, which presents with fatigable double vision, ptosis, difficulty in swallowing and speech, and weakness in the arms and legs. Typically, these symptoms get worse with activity and improve with rest. They are more severe toward the end of the day. The symptoms can be restricted to the eyelids and extraocular muscles, but sometimes they are generalized and affect the bulbar and proximal arm and leg muscles as well.

Question: What symptoms are not expected in patients with myasthenia gravis?
Answer: Impairment of memory, urinary incontinence, numbness, lack of sensation or incoordination are the symptoms that are not expected in patients with myasthenia gravis. If they exist, then another explanation should be sought.

Question: What are the voice changes that are seen in patients with myasthenia gravis?
Answer: Patients with bulbar myasthenia often notice that their voice becomes quieter, or may disappear altogether, during continued conversation.

Question: Is chewing difficulty a feature of myasthenia gravis?
Answer: Yes. Many patients are unable to chew strongly towards the end of a meal and many patients tend to sit with their jaw supported in one hand in order to prevent it from hanging open and to facilitate chewing and talking.

Question: What does the tongue look like in patients with myasthenia gravis?
Answer: A grooved tongue, or what is called a triple furrowed tongue, is seen in longstanding cases. The tongue has three, long, longitudinal furrows in this situation.

Question: What is the most common differential diagnosis of myasthenia gravis?
Answer: Hysteria. Early in the disease, myasthenic symptoms may suggest hysterical conversation, in particular the fluctuating weakness.

Question: Is myasthenia gravis associated with thymoma?
Answer: Yes. About 15% of patients with myasthenia gravis have a malignant tumor of the thymus gland, which is called thymoma. Patients with myasthenia and thymoma are usually older and have a shorter history of muscle weakness, with a more severe and progressive course.

Question: How is myasthenia gravis diagnosed?
Answer: The diagnosis is based on the demonstration of undue fatigability of the ocular, bulbar and/or proximal arm or leg muscles during examination. Increased acetylcholine receptor antibody titer is the most specific test for myasthenia gravis. Demonstration of decremental response with repetitive nerve stimulation is the neurophysiological hallmark of the diagnosis of myasthenia gravis. Single fiber EMG is the most sensitive test.

Question: Does the level of acetylcholine receptor antibody titer correlate with the severity of the disease?
Answer: No. The level of the acetylcholine receptor antibody titer does not correlate well with the severity of the disorder.

Question: What is the treatment of myasthenia gravis?
Answer: Myasthenia gravis is a treatable disease. Cholinesterase inhibitors are useful, in particular, early in the disease. Pyridostigmine (Mestinon) is the main drug, which is effective to reduce the symptoms of myasthenia gravis, but it does not change the natural course of the disease.

Question: What is the role of thymectomy in myasthenia gravis?
Answer: Thymectomy is considered to be a routine procedure for all patients with myasthenia gravis, if they can tolerate surgery. However, there is no role for emergency thymectomy in myasthenia gravis and is recommended to be done after the disease is controlled. Thymectomy may increase the long-term remission rate of myasthenia gravis.

Question: What is the role of steroids in the treatment of myasthenia gravis?
Answer: Steroids are useful in inducing remission. However, because of the possible side effects, the treatment with steroids is reserved for severe cases.

Question: What is the role of intravenous immunoglobulin therapy in treatment of myasthenia gravis?
Answer: IV IG produces beneficial response that is usually noticed within 4-5 days of initiation of treatment in 85% of cases. It has been used especially in myasthenia crisis in a daily dose of 0.4 Gm/kg of body weight for five days.

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