Myasthenia gravis is a disorder that affects the muscles. The disease can affect any voluntary (skeletal) muscle can be affected, but it's more likely to involve some muscles than others. The muscles that control eye movement, the eyelids, facial expression, and swallowing are the ones most frequently affected by the disorder.

Muscle weakness is the central problem in myasthenia gravis. Weakness usually increases with continued activity but improves after periods of rest.

The degree of weakness can vary throughout the day, sometimes changing within a few minutes. It may vary from day to day and over long periods of time. Patients can also experience periods without weakness followed by a decline in strength. Symptom-free periods are sometimes called remissions, while a return of symptoms is known as a relapse.

Myasthenia gravis first affects the muscles of the eyes in most patients, although some patients initially experience problems with chewing, swallowing, or speaking. In about 20 percent of patients, symptoms are limited to eye problems. This is the mildest form of the disorder and is called ocular myasthenia gravis. For other patients, the severity of symptoms and the number of muscles involved can vary greatly. Symptoms of myasthenia gravis often become more widespread within several months of the onset of the disease. Symptoms reach their peak within a year in about two-thirds of patients.

Weakness of the eyelid muscles can cause a drooping of one or both eyelids. This is called ptosis. Weakness of the muscles that control the movement of the eye can cause blurred or double vision. Double vision is sometimes called diplopia.

When myasthenia gravis affects the facial muscles or the muscles of the throat, a variety of problems can occur, depending on the exact muscles affected. Patients may have problems with facial expression. Some patients may experience problems with speaking, or dysarthria. Patients may also have problems with swallowing, a condition known as dysphagia.

Some patients may experience weakness in the neck and/or arms and legs. These symptoms rarely occur alone. They usually coincide with the symptoms discussed above. When these muscles are affected, patients can have difficulty performing any activity that uses these muscles.

In some cases, the muscles that control breathing can be affected. When this occurs, patients usually experience shortness of breath, difficulty taking a deep breath, and coughing. If the weakness is severe, patients may need to receive treatment in a hospital.

There are conditions that can cause symptoms to worsen. Heat, including heat from the sun, hot showers or baths, and hot drinks, can result in increased weakness. Emotional stress and other illnesses can also aggravate the symptoms of myasthenia gravis.

Although there is no known cure for myasthenia gravis, there have been major advances in treatment in recent years. With proper treatment, most patients have an excellent chance of reducing their symptoms and leading normal, productive lives.

References

First published April 1, 2000
Last updated November 25, 2002
Copyright © 2000 Accordant Health Services, Inc. All Rights Reserved.

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