By Carla Schick
Myasthenia gravis (MG) is a chronic health condition that affects many of our immune globulin (IG)-treated patients and countless others who have gone undiagnosed. Since June is MG awareness month, we thought it might be a good idea to talk about the various tests and treatment options for MG.
What Is MG?
Myasthenia gravis is a chronic autoimmune neuromuscular disease that affects the strength of voluntary muscles, including eye and eyelid movement, facial expressions, chewing, talking, swallowing and occasionally other muscle groups. The cause of MG lies in the neuromuscular junction - the location where nerve cells connect with the muscles they control. When normal communication is possible between the nerve cells and their corresponding muscles, impulses will travel down the nerve and release a neurotransmitter called acetylcholine. As the acetylcholine travels from the neuromuscular junction and binds to acetylcholine receptors, the receptors become activated and generate a muscle contraction. However, when the receptors are blocked by antibodies, communication between the nerve and muscle is interrupted, preventing the muscles from contracting. These antibodies are produced by the body's immune system to guard against foreign organisms, but instead of assisting the body, the antibodies mistakenly go on the attack, resulting in destroyed receptors.
Because muscle weakness is often a symptom of many disorders, a diagnosis of MG is often delayed, particularly if a patient displays only mild or restricted muscle weakness. The first step the doctor can take is to review the patient's medical history and conduct physical and neurological examinations. The physician can also check for impaired eye movement, one of the first perceivable symptoms. If MG is the suspected diagnosis, a special blood test can detect the presence of acetylcholine receptor antibodies, which are abnormally high in most MG patients.
Another exam is the edrophonium test, which uses intravenous administration of edrophonium chloride to temporarily block the breakdown of acetylcholine and momentarily increase the levels of acetylcholine at the neuromuscular junction. A nerve conduction study records weakening muscle responses that may demonstrate impaired nerve-to-muscle transmission.
A small fiber electromyography (EMG) can measure the electrical potential of muscle cells when single muscle fibers are stimulated by electrical impulses. Muscle fibers in MG patients do not respond well to repeated electrical stimulation. Diagnostic CT or MRI scans of the chest can be used to detect the presence of thymoma, a tumor that can develop on the thymus gland. The tumors are generally benign, but an enlarged thymus gland may give the wrong commands to developing immune cells, resulting in the production of acetylcholine receptor antibodies.
Currently, there is no cure for MG, but there are many treatment options to help control and reduce muscle weakness. One of these treatments is intravenous immunoglobulin (IVIG) therapy. Although IVIG is an off-label treatment method for MG, many patients have found that IVIG infusions have given them more than encouraging results. Lisa Langhals, an MG patient who was diagnosed seven years ago, says: "It was like being in a dark room and then turning on the light. The first day or so, you don't feel well. But then, it's like it's all gone. The change is that drastic."
Other treatment options include plasmapheresis, a procedure in which serum containing the abnormal antibodies is removed from the blood while cells are replaced. Immunosuppressive medications like prednisone can be taken to improve muscle strength by suppressing the production of abnormal antibodies. And a thymectomy can be performed, which may reduce symptoms in some MG patients.
These are just a few of the tests and treatment options available to MG patients and those who think they may be suffering from MG.
To learn more about the information found in this blog, please visit the National Institute of Neurological Disorders and Stroke's Myasthenia Gravis Fact Sheet.
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