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An electromyography may be used to diagnose myasthenia gravis.

An electromyography may be used to diagnose myasthenia gravis.
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Myasthenia gravis

3-minute read

Key facts

  • Myasthenia gravis is an autoimmune disease that causes a breakdown in communication between the nerves and muscles.
  • The condition often begins in the eye muscles or face. It can be hard to control your eye and eyelid movements, or to talk, chew and swallow.
  • It can't be cured, but the symptoms can be managed.
  • Myasthenia gravis can be diagnosed using several tests and scans, including blood tests, an electromyography and imaging such as CT scans and MRI.

What is myasthenia gravis?

Myasthenia gravis is a rare disease of the neuromuscular system. Its main symptom is muscle weakness and it is caused by a breakdown in communication between the nerves and muscles.

Myasthenia gravis can’t be cured but treatments are available to help manage the symptoms.

The name of the disease comes from the Greek ‘myasthenia’, meaning muscle weakness, and the Latin ‘gravis’, meaning severe.

What are the symptoms of myasthenia gravis?

Myasthenia gravis often begins in the eye muscles or elsewhere on the face. If you have the condition it can be hard to control your eye and eyelid movements, and to talk, chew and swallow.

The symptoms can appear suddenly or take weeks to develop. They might also come and go. They include

  • drooping of one or both eyelids
  • blurred or double vision
  • unsteady walking
  • weak hands, fingers, legs, and neck
  • a change in facial expression
  • shortness of breath
  • trouble swallowing

Most people with myasthenia gravis say the muscle weakness is often worse when they are active and improves after they rest.

If you notice any of these symptoms, you should see your doctor.

What causes myasthenia gravis?

Myasthenia gravis is an autoimmune disease. This means it is caused by your body’s immune system.

People with myasthenia gravis are more likely than others to have relatives with other autoimmune diseases, such as Graves' disease, rheumatoid arthritis and lupus.

Babies can get a form of myasthenia gravis from their mothers, but this is usually temporary.

It is not understood why some people get autoimmune diseases while others do not.

How is myasthenia gravis diagnosed?

To diagnose myasthenia gravis, your doctor will talk to you and examine you. You might also have some tests to confirm a diagnosis, such as:

  • a blood test
  • electromyography (a test that measures muscle function)
  • injection of the drug Tensilon to see its effect on muscle strength
  • imaging such as a chest x-ray, a CT scan or an MRI, to look for abnormalities in the thymus gland (a small gland in the upper chest)

How is myasthenia gravis treated?

Myasthenia gravis is one of the most treatable neuromuscular disorders. Common treatments include:

  • medicines to improve muscle strength or hold back the immune system
  • treatment to filter the blood through a machine which removes the bad antibodies that occur in myasthenia gravis
  • surgery to remove the thymus gland where the antibodies that attack the muscles are produced

Often, a combination of treatments is used.

Complications of myasthenia gravis

Myasthenic crisis is a medical emergency that develops when the muscles that control breathing are severely weakened. A crisis is usually triggered by an infection, emotional stress, or a bad reaction to medication. The person will usually need to have a ventilator breathe for them in hospital.

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Last reviewed: March 2020

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