Myasthenia Gravis

What is myasthenia gravis?

Myasthenia gravis (MG) is a complex, autoimmune disorder in which antibodies destroy neuromuscular connections. This causes problems with the nerves that communicate with muscles. MG affects the voluntary muscles of the body, especially the eyes, mouth, throat, and limbs.

In the US, MG affects about 14 people in 100,000. The disease is two to three times more common in women than men up to the age of 40; however, in older persons, men and women are affected at similar rates.

What causes myasthenia gravis?

Myasthenia gravis may be inherited as a rare, genetic disease, it may be acquired by babies born to mothers with MG, or the disorder may develop spontaneously later in life.

What are the types of myasthenia gravis?

MG occurs rarely in persons younger than 10 years old. However, there are three types of MG in children, including the following:

congenital MG - this is a very rare, non-immune form of MG that is inherited as an autosomal recessive disease. This means that both males and females are equally affected and that two copies of the gene, one inherited from each parent, are necessary to have the condition. Symptoms of congenital MG usually begin in the baby's first year and are life-long.
transient neonatal MG - between 10 percent and 20 percent of babies born to mothers with MG may have a temporary form of MG. This occurs when antibodies common in MG cross the placenta to the developing fetus. Neonatal MG usually lasts only a few weeks, and babies are not at greater risk for developing MG later in life.
juvenile MG - this auto-immune disorder develops typically in female adolescents - especially Caucasian females. It is a life-long condition that may go in and out of remission. About 10 percent of MG cases are juvenile-onset.

In adults, MG may occur at any age, although symptoms begin to appear more often between the ages of 20 to 30 in women and between the ages of 50 to 60 in men.

What are the symptoms of myasthenia gravis?

The following are the most common symptoms of myasthenia gravis. However, each individual may experience symptoms differently. Symptoms may include:

visual problems, including drooping eyelids (ptosis) and double vision (diplopia) - about 40 percent of persons with MG have symptoms such as these at first, and up to 85 percent will develop these symptoms in the course of their disease
severe muscle weakness and fatigue that may vary rapidly in intensity over days or even hours
facial muscle involvement causing a mask-like appearance; a smile may appear more like a snarl
difficulty in swallowing and/or pronouncing words
weakness of the neck and/or limbs

The symptoms of myasthenia gravis may resemble other conditions. Always consult your physician for a diagnosis.

A primary characteristic of MG results in the response of an affected person to certain medications. When given an anticholinesterase medication, such as neostigmine (Prostigmin) or edrophonium (Tensilon), muscle weakness often dramatically improves for a brief time.

Exacerbations (worsening of symptoms) and remissions (easing of symptoms) may occur periodically during the course of MG. Remissions, however, are only rarely permanent or complete.

How is myasthenia gravis diagnosed?

The diagnosis of myasthenia gravis is made after the sudden or gradual onset of specific symptoms and after diagnostic testing. During the physical examination, the physician obtains a complete medical history, and may also ask if there is a family history of any medical problems.

Diagnosis of MG is usually confirmed with a Tensilon test. With this test, a small amount of medication (Tensilon) is injected. If the person has MG, an immediate, but brief, increase in muscle tone is noted.

Other diagnostic tests that may be performed to help confirm the diagnosis of myasthenia gravis include:

blood tests - anti-acetylcholine receptor antibodies are present in the blood of over 80 percent of affected persons.
genetic tests - diagnostic tests that evaluate for conditions that have a tendency to run in families.
electromyogram (EMG) - a test that measures the electrical activity of a muscle or a group of muscles. An EMG can detect abnormal electrical muscle activity due to diseases and neuromuscular conditions.
muscle biopsy - a small sample of the muscle is removed and examined to determine and confirm a diagnosis or condition.

Treatment of myasthenia gravis:

Specific treatment for myasthenia gravis will be determined by your physician based on:

your age, overall health, and medical history
extent of the condition
your tolerance for specific medications, procedures, or therapies
expectations for the course of the condition
your opinion or preference

There is no cure for MG, but the symptoms can sometimes be controlled. Myasthenia gravis is a life-long medical condition and the key to medically managing MG is early detection.

The goal of treatment is to prevent respiratory problems and provide adequate nutritional care since the swallowing and breathing muscles are affected by this condition.

Treatment may include:

medications - anticholinesterase medications, such as Prostigmin or Tensilon; steroids; and/or immunosuppressive (suppress the immune system’s response) medications may be used.
thymectomy - surgical removal of the thymus gland. The role of the thymus gland in MG is not fully understood, and the thymectomy may or may not improve symptoms. However, the thymus gland exhibits abnormalities in about 70 percent of adults affected with MG.
plasmapheresis - a procedure that removes abnormal antibodies from the blood and replaces the blood with normal antibodies through donated blood.
immunoglobulin - a blood product that helps to decrease the immune system’s attack on the nervous system, given intravenously (IV).

The extent of the problems is dependent on the severity of the condition and the presence of other problems that could affect the individual. In severe cases, a breathing machine may be required to help the person breathe easier.

The healthcare team educates the family after hospitalization on how to best care for the person at home and outlines specific clinical problems that require immediate medical attention by their physician. A person with MG requires frequent medical evaluations throughout his/her life.

It is important to allow as much independent function and self care as possible and to promote appropriate activities to ensure a sense of normalcy.

What is myasthenia crisis:

Myasthenia crisis is a condition of extreme muscle weakness, particularly of the diaphragm and chest muscles that support breathing. Myasthenia crisis may be caused by a lack of MG medication or by other factors, such as a respiratory infection, emotional stress, surgery, or some other type of stressor. In severe crisis, a person may have to be placed on a ventilator to assist breathing until muscle strength returns with treatment.

Precautions, which may help to prevent or minimize the occurrence of myasthenia crisis, include, but are not limited to, the following:

taking anticholinesterase medications 30 to 45 minutes prior to meals to reduce the risk of aspiration (food entering the lung passages)
taking anticholinesterase medications precisely as ordered by the physician to help maintain the strength of the breathing muscles
avoiding crowds and contact with people with respiratory infections, such as a cold or the flu
taking in proper nutrition to maintain optimal weight and muscle strength
alternate performance of physical activities with periods of rest
using stress-reduction techniques and avoiding emotional extremes
notify any healthcare provider of your condition when any medications are being prescribed, as certain medications may interfere either with the disease or the action of the medications you take for MG

Click here to view the
Online Resources of Nervous System Disorders

return to top of page