Myasthenia Gravis

What is myasthenia gravis?

Myasthenia gravis (called “MG” here) is a condition that causes weakness in certain muscles. These include:

  1. Muscles in the eyelids and around the eyes – If MG only affects these muscles, doctors call it “ocular myasthenia gravis.” About half of all people with MG have this type.

  2. Jaw muscles

  3. Arm or leg muscles

  4. Muscles that help with breathing

Myasthenia gravis happens because of a problem with the body’s infection-fighting system, called the “immune system.” The immune system normally makes proteins called “antibodies,” which help to prevent infection. However, in people with MG, the immune system makes some antibodies that attack the connections between nerves and muscles by mistake.

What are the symptoms of myasthenia gravis?

The main symptom is muscle weakness. It can come and go, and is often worse later in the day. It can cause:

  1. Droopy eyelids

  2. Blurry vision or double vision

  3. Trouble chewing food - The jaw muscles might feel tired about halfway through a meal.

  4. Trouble swallowing

  5. Trouble talking – A person might speak in a lower voice than usual, or sound like he or she has a cold or stuffy nose.

  6. Loss of expression on the face

  7. Head that feels heavy or drops forward

  8. Trouble breathing – A person might feel short of breath, take extra breaths, or feel like it takes a lot of effort to breathe.

  9. Weakness – It might be hard to lift the arms or legs, open the fingers, or lift a foot.

Will I need tests?

Yes. The doctor or nurse will do an exam and learn about your symptoms. You might also have:

  1. Blood tests to look for certain antibodies that are found in people with MG.

  2. Electrical tests of nerves and muscles – These can show if nerves are carrying electrical signals normally and if muscles are responding correctly to electrical signals.

  3. Imaging tests, such as CT or MRI scans – Most people with myasthenia gravis have some changes in the thymus gland. This is a gland in the chest that is part of the immune system. Imaging tests can show changes, including a tumor on the thymus gland. Some people have a CT scan or MRI of the head. It can show if a different condition is causing symptoms.

  4. Ice pack test – During this test, a doctor puts a cool pack on the eyelids. If the eyelids open better after resting under the cool pack, this could be a sign of MG.

How is myasthenia gravis treated? — Treatments include:

  1. Medicines to treat muscle weakness, such as pyridostigmine.

  2. Medicines that treat the immune system over time.

  3. Fast-acting immune system treatments, such as:

    1. A medicine called “intravenous immune globulin” (IVIG) – This medicine is given through an IV.

    2. Plasma exchange (also called “plasmapheresis”) – For this treatment, a machine pumps blood from the body and removes substances from the blood that are attacking the nerves and muscles. Then the machine returns the blood to the body.

  4. Surgery to remove the thymus gland

If MG attacks the muscles that help with breathing, it can cause severe breathing problems. These are usually treated in the intensive care unit (also called the “ICU”).

What if I want to get pregnant?

If you want to get pregnant, talk to your doctor or nurse before you start trying to have a baby. Pregnancy can make MG worse.

What else should I know about myasthenia gravis?

People who have MG that affects more than just the eyes can have serious problems if they get the flu or pneumonia. For this reason, it is especially important that they get the flu shot every year and the pneumonia vaccine at least one time.

Some medicines can make MG worse. Talk to your doctor or nurse before you take any medicines, including over-the-counter medicines. If you get a prescription for a new medicine, ask if it is safe to take when you have MG.


This topic retrieved from UpToDate on: January 22, 2019.

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