Myasthenia gravis (MG) is a disorder of the neuromuscular junction that causes muscle weakness because nerve impulses are not adequately transmitted to muscles.
[Learn about the MG Support Group at Wake Forest Baptist Health.]
MG is an auto immune disease, meaning that the body attacks itself. Antibodies that would normally protect the body from foreign organisms block, change or destroy the impulses at the neuromuscular junction. This prevents muscles from operating properly.
The muscles most often affected are those that control eye and eyelid movement, facial expression and swallowing. Other muscles may be affected as well.
About 36,000 people in the United States have the condition, which commonly affects young adult women and older men. It can occur at any age, and is life threatening when it affects the respiratory system.
However, the 1st year of muscle weakness can be the worse. With care and treatment, good muscle function can be maintained in many patients.
Neonatal myasthenia gravis generally disappears after birth.
Myasthenia Gravis Symptoms
The most common early symptoms are double vision, droopy eyelids, and difficulty swallowing, chewing or talking.
A common trait of this disease is muscle weakness that may increase during periods of activity and improve after periods of rest. Myasthenia gravis may come on gradually or develop rapidly.
The degree of muscle weakness varies tremendously and can range from a localized form limited to eye muscles to a generalized form in which many muscles are affected.
The thymus gland, which is part of the immune system, can be abnormal in MG patients or tumors can be developed on the gland.
Diagnosing myasthenia gravis can be difficult because muscle weakness is common in many other disorders.
In addition to a medical history and physical and neurological examinations, the doctor may ask for other testing. This may include a blood test to detect elevated antibodies, an edrophonium test to detect impact on muscles, a nerve conduction study for specific muscle fatigue, an electromyography (EMG) to test single muscle fibers, computed tomography (CT) or magnetic resonance imaging (MRI) to identify an abnormal thymus gland or pulmonary function testing to measure breathing strength.
Myasthenia Gravis Treatment
Medications aimed at improving muscle weakness and strength are used to help control myasthenia gravis, as well as a number of procedures, all dependent on the patient's age, degree of symptoms and related medical problems.
Certain anticholinesterase agents improve neuromuscular transmission. Immunosuppressive drugs help suppress the production of abnormal antibodies.
Removal of the thymus gland can improve symptoms and, in some cases, cure patients. Other procedures can be helpful during periods of weakness. They include removing abnormal antibodies from the blood and providing the body with normal antibodies from donated blood.
A crisis or medical emergency in which the respiratory muscles are affected can be triggered by infection, fever, stress or adverse reaction to medication. This requires immediate attention and the patient may need a respirator.
Researchers are still trying to learn what causes the autoimmune response in myasthenia gravis and to define the relationship between the thymus gland and the condition.
One study by the National Institute of Neurological Disorders and Stroke (NINDS) is testing the efficacy of intravenous immune globulin in MG patients to see if this treatment safely improves muscle strength.
Another NINDS study attempts to understand the molecular basis of synaptic transmission in the nervous system.
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