Myasthenia Gravis-Als

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Myasthenia gravis is an autoimmune disorder that impairs communication between nerves and muscles, resulting in episodes of muscle weakness.

• Myasthenia gravis may result from malfunction of the immune system
• People usually have drooping eyelids and double vision, and muscles become unusually tired and weak after exercise
• Response to a drug given intravenously helps doctors determine whether people may have myasthenia gravis
• Electromyography, blood tests, and imaging tests are needed to confirm the diagnosis.

Myasthenia gravis disease is more common among women. It usually develops in women between the ages of 20 and 40. However, the disorder may affect men or women at any age. Rarely, it begins during childhood.

In myasthenia gravis, the immune system produces antibodies that attack one type of receptor on the muscle side of the neuromuscular junction—the receptors that respond to the neurotransmitter acetylcholine. As a result, communication between the nerve cell and the muscle is disrupted. What causes the body to attack its own acetylcholine receptors—an autoimmune reaction—is unknown. According to one theory, malfunction of the thymus gland may be involved. In the thymus gland, certain cells of the immune system learn how to differentiate between the body and foreign substances. The thymus gland also contains muscle cells (myocytes) with acetylcholine receptors. For unknown reasons, the thymus gland may instruct the immune system cells to produce antibodies that attack the acetylcholine receptors. People may inherit a predisposition to this autoimmune abnormality. About 65% of people who have myasthenia gravis have an enlarged thymus gland, and about 10% have a tumor of the thymus gland (thymoma). About half of thymomas are cancerous (malignant). Some people with the disorder do not have antibodies to acetylcholine receptors but have antibodies to an enzyme involved in the formation of the neuromuscular junction instead. These people may require different treatment.

The disorder may be triggered by infections, surgery, or use of certain drugs.

Neonatal myasthenia develops in 12% of babies born to women who have myasthenia gravis. Antibodies against acetylcholine receptors, which circulate in the blood, may pass from a pregnant woman through the placenta to the fetus. In such cases, the baby has muscle weakness that disappears several days to a few weeks after birth. The remaining 88% of babies are not affected.

Symptoms

Episodes of worsened Myasthenia gravis symptoms (exacerbations) are common. At other times, symptoms may be minimal or absent.

The most common symptoms are:

• Weak, drooping eyelids
• Weak eye muscles, which cause double vision
• Excessive weakness of affected muscles after they are used

The weakness disappears when the muscles are rested but recurs when they are used again.

In 40% of people with myasthenia gravis, the eye muscles are affected first, but 85% eventually have this problem. In 15% of people, only the eye muscles are affected, but in most people, the whole body is affected. Difficulty speaking and swallowing and weakness of the arms and legs are common. Hand grip may alternate between weak and normal. This fluctuating grip is called milkmaid's grip. Neck muscles may become weak. Sensation is not affected.

When people with myasthenia gravis use a muscle repetitively, the muscle usually becomes weak. For example, people who once could use a hammer well become weak after hammering for several minutes. However, muscle weakness varies in intensity from hour to hour and from day to day, and the course of the disease varies widely.

About 15% of people have severe episodes (called myasthenia crisis), sometimes triggered by an infection. The arms and legs may become extremely weak, but even then, they do not lose sensation. In some people, the muscles needed for breathing weaken. This condition is life threatening.

Diagnosis

Doctors suspect myasthenia gravis in people with episodes of weakness, especially when the eye or facial muscles are affected or when weakness increases with use of the affected muscles and disappears with rest. Because acetylcholine receptors are damaged, drugs that increase levels of acetylcholine can be used to help confirm the diagnosis. People are asked to exercise the affected muscle until it tires. Then they are given the drug. If it temporarily and quickly improves muscle strength, myasthenia gravis is a possible diagnosis.

Other diagnostic tests are needed to confirm the diagnosis. They include electromyography (stimulating muscles, then recording their electrical activity) and blood tests to detect antibodies to acetylcholine receptors and sometimes the other antibodies present in people with the disorder. Blood tests are also done to check for other disorders. Computed tomography (CT) or magnetic resonance imaging (MRI) of the chest is done to assess the thymus gland and to determine whether a thymoma is present.

Treatment

Individual myasthenia gravis treatment may vary depending upon the patient and their desire to receive tradition treatment, alternative treatment or integrative treatment for the disease.  It is vital that persons diagnosed with, or suspected of having myasthenia gravis consult with their health care provider to assure proper evaluation, treatment and interpretation of information contained on this site.

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