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Myasthenia Gravis
Myasthenia gravis is an autoimmune disease that gradually causes muscles to lose their strength and function. Autoimmune diseases are caused by the body making substances called antibodies that attack a person's own tissues. In myasthenia gravis, these antibodies are made against receptors in the neuromuscular junction (the area where nerve transmission makes a muscle do its work). Myasthenia gravis affects individuals differently, and each person may present with weakness in different sets of muscles. The April 20, 2005, issue of JAMA includes an article about diagnosing myasthenia gravis.
SYMPTOMS OF MYASTHENIA GRAVIS
- Muscle weakness
- Double vision
- Weak eyelids
- Difficulty speaking or smiling
- Difficulty chewing and swallowing
Muscle weakness related to myasthenia gravis usually occurs after the muscle group is used and lessens if the muscle group has some rest. This is called fatigable weakness and is an important characteristic for the diagnosis of myasthenia gravis.
DIAGNOSIS
Your doctor will take a medical history, asking especially about the type of muscle weakness, what makes it better, and what makes it worse. A physical examination may reveal weakness of the extremities, the eye muscles, or difficulty in facial expression. Several tests may be used to help diagnose myasthenia gravis:
- Ice pack or rest test (simple procedures that temporarily improve eyelid drooping)
- Edrophonium test (a medication given through an intravenous line, temporarily improving strength in patients with myasthenia gravis)
- Blood tests may show antibodies to the receptor at the neuromuscular junction
- Nerve conduction studies may show fatigable weakness in individual muscle groups
TREATMENT
Symptoms of myasthenia gravis can usually be improved with medications that increase the amount of acetylcholine (a neurotransmitter) at the neuromuscular junction. Treatments involving the immune system include injections of intravenous immunoglobulin, immunosuppressive medications, and plasmapheresis (removal of antibodies from the blood). If an individual's myasthenia is found to be related to abnormalities in the thymus gland located at the base of the neck underneath the breastbone (sternum), a thymectomy (surgical removal of the thymus gland) may help to improve the symptoms. When respiratory (breathing) muscles fail, this is called a myasthenic crisis. This type of respiratory failure is an emergency. It may require intensive care and use of a ventilator to assist breathing. Some factors leading to a myasthenic crisis include infection, fever, medication effects, or even stress.
FOR MORE INFORMATION
INFORM YOURSELF
To find this and previous JAMA Patient Pages, go to the Patient Page link on JAMA's Web site at http://www.jama.com.
Sources: National Institute of Neurological Disorders and Stroke; American Academy of Neurology; Myasthenia Gravis Foundation of America
The JAMA Patient Page is a public service of JAMA. The information and recommendations appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JAMA suggests that you consult your physician. This page may be photocopied noncommercially by physicians and other health care professionals to share with patients. Any other print or online reproduction is subject to AMA approval. To purchase bulk reprints, call 718/946-7424.
TOPIC: NEUROMUSCULAR DISORDERS
Janet M. Torpy, MD, Writer;
Tiffany J. Glass, MA, Illustrator;
Richard M. Glass, MD, Editor
JAMA. 2005;293:1940.
RELATED ARTICLE
Does This Patient Have Myasthenia Gravis?
Katalin Scherer, Richard S. Bedlack, and David L. Simel
JAMA. 2005;293(15):1906-1914.
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