The name myasthenia gravis is Greek and Latin meaning "grave muscle weakness." It's an autoimmune disease characterized by weakness and the rapid fatigue of voluntarily controlled muscles. The weakness is caused by antibodies that block muscle cells from receiving chemical messages to move the body. As a result, muscles don't function properly and become easily fatigued.
Common muscle groups that are affected include those involved in the eyes, facial movement, swallowing, speaking, lifting up the arms, rising to stand and walking up stairs. When the disorder affects muscles needed for breathing, the results can be life-threatening. Myasthenia gravis affecting multiple muscle groups throughout the body is called generalized myasthenia gravis.
For more information about myasthenia gravis, or to schedule an appointment at Virginia Mason's Neuroscience Institute, call (206) 341-0420.
Myasthenia gravis is an autoimmune disease, which means the body's antibodies mistake something in the body as foreign and destroy it. In myasthenia gravis, antibodies attack receptor sites on the muscle cells, preventing them from receiving sufficient chemical messages from nerve cells to function normally.
It is thought that the thymus gland, an immune system gland located beneath the breastbone, may be responsible for the production of these antibodies. In some people with myasthenia gravis, the thymus is abnormally large. About 15 percent of all myasthenia gravis patients are found to have a thymoma, a tumor of the thymus. Although most thymomas are benign, the thymus is usually removed. Even if no tumor is present, removal of the thymus seems to improve symptoms in some patients.
Because muscles do not receive sufficient signals from nerve cells, myasthenia gravis causes muscle weakness that worsens with repeated use. Resting can improve muscle performance causing the weakness to come and go. The disorder can affect any voluntary muscles, but specific muscle groups are frequently involved, including:
Sometimes myasthenia gravis is diagnosed long after onset due to mild symptoms, or because symptoms are attributed to another condition.
A diagnosis begins with a complete physical and neurological examination to evaluate symptoms and muscle function. Eye movement is observed for impairment, as is any additional muscle weakness. If myasthenia gravis is suspected, there are specific tests to help confirm the diagnosis, including:
There is no cure for myasthenia gravis, but treatment can result in prolonged periods without any symptoms. The choice of treatment can depend on several factors, including the patient's age, overall health, severity of symptoms and rate of disease progression.
Types of medications used to relieve symptoms include:
Other treatments for myasthenia gravis include:
Thymectomy, the surgical removal of the thymus gland (which often is abnormal in myasthenia gravis patients), can reduce or eliminate symptoms in some patients. About 15 percent of the people who have myasthenia gravis have a tumor in their thymus and seem to benefit most from the thymectomy procedure.
Due to the risks involved in any surgical procedure, people with myasthenia gravis who don't have a tumor in the thymus should discuss the pros and cons of surgery with their doctor. In general, a thymectomy may not be recommended if symptoms are generally mild, only involve the eyes or if the patient is over 60 years old.
For more information about myasthenia gravis, contact Virginia Mason's Neuroscience Institute at (206) 341-1900.