Understanding Myasthenia Gravis -- the Basics

Medically Reviewed by Christopher Melinosky, MD on August 23, 2022
Written by WebMD Editorial Contributors
6 min read

Myasthenia gravis is a chronic condition that causes muscles to tire and weaken easily. For example, if you have myasthenia gravis, you may notice that during a meal, your jaw muscles become tired and weak, interfering with your ability to chew food. After you have rested for a little while, the muscles may become strong again, allowing you to resume eating.

This waxing-and-waning weakness of muscles, worsening with use and improving with rest, is a hallmark of this disease. There typically are periods when you may notice more symptoms (called an exacerbation), interspersed with periods when symptoms decrease or disappear (remission).

Myasthenia gravis affecting multiple muscle groups throughout the body is called generalized myasthenia gravis. Other common muscle groups that are affected may make it difficult for you to chew, swallow, smile, shrug, lift your arm up, grip, rise to a stand, or walk up stairs. When the muscles needed for breathing are affected, a patient is said to be in myasthenic crisis. This is a life-threatening situation.

Though anyone can get myasthenia gravis, those most likely to do so are women between ages 20 and 40 or men between ages 50 and 70. If a woman with myasthenia gravis gives birth, the baby may have some temporary, and potentially life-threatening, muscle weakness (neonatal myasthenia) because of antibodies that have transferred from the mother's bloodstream. Typically, during the baby's first weeks of life, the antibodies are cleared from the baby's circulation and the baby develops normal muscle tone and strength.

The disease most commonly affects muscles that control eye and eyelid movement, so the first symptoms you notice may be eyelid drooping and/or blurred or doubled vision. The majority will go on to have weakness in other muscle groups in 1 or 2 years.

General symptoms of myasthenia gravis include:

  • Weakness in your eye muscles
  • Drooping eyelids
  • Double vision
  • Blurred vision
  • Change in your facial expression
  • Trouble swallowing
  • Shortness of breath
  • Problems speaking
  • Problems walking and lifting things
  • Trouble holding up your head

If the muscles you use to breathe get weak enough that you can’t control them, it’s called a myasthenic crisis. This is a medical emergency that may require a ventilator to help you breathe. Around 15% to 20% of people with myasthenia gravis have at least one myasthenic crisis. They can be caused by an infection, stress, surgery, or a reaction to medication.

Under normal conditions, nerves direct your muscles to work by sending a message through an area called a receptor. The chemical that delivers the message is called acetylcholine. When acetylcholine binds to a nerve receptor, your muscle knows to contract. In myasthenia gravis, your body attacks its acetylcholine receptors.

Myasthenia gravis is considered to be an autoimmune disorder. In an autoimmune disease, some of the body's antibodies (special proteins in your body that are supposed to be programmed to fight foreign invaders such as bacteria, viruses, or fungi) mistake a part of your own body as foreign, resulting in its destruction. In the case of myasthenia gravis, antibodies block, attack or destroy the acetylcholine receptors needed for muscle contraction.

No one knows exactly what causes the body to begin producing the antibodies that destroy acetylcholine receptors. In some cases, the process seems to be related to the thymus gland, which helps produce antibodies.

About 15% of all myasthenia gravis patients are found to have a thymoma, a tumor of the thymus. Although most thymomas are benign (not cancerous), the thymus is usually removed (thymectomy) to prevent the potential spread of cancer. In fact, thymectomy seems to improve symptoms of myasthenia gravis in some patients, even if no tumor is present.

To see if you have myasthenia gravis, your doctor will start with a neurological exam. This includes a test of your:

  • Reflexes
  • Muscle strength
  • Muscle tone
  • Touch
  • Sight
  • Coordination
  • Balance
  • Fatigability (how soon your muscles weaken)

Then you’ll have tests to help look more closely at symptoms of myasthenia gravis. These include:

  • Edrophonium test. Your doctor injects you with a chemical called edrophonium chloride to see if it improves your muscle strength. If it does, that’s a sign you might have myasthenia gravis.
  • Ice pack test. If you have a drooping eyelid, your doctor may put an ice pack on it for 2 minutes to see if the low temperature has an effect on it.
  • Blood test. Your doctor will draw some of your blood and send it to a lab to check for certain antibodies that affect muscle nerve receptors.
  • Repetitive nerve stimulation. This test uses electrodes on your muscles to send small electrical pulses to see if your nerves react to the signals.
  • Single-fiber electromyography (EMG). Your doctor puts a thin wire electrode through your skin and into a muscle. It can test the electrical activity between your brain and your muscles.
  • Imaging. Your doctor may suggest a CT scan or MRI to look more closely for a tumor on your thymus that could be causing symptoms.
  • Pulmonary functioning tests. Your doctor tests your breathing to see if your lungs are affected by myasthenia gravis.

Your treatment will depend on your age, how severe your symptoms are, and how fast the condition is progressing. You might need one or several treatments together. Your doctor may recommend a medication such as:

  • Cholinesterase inhibitors. These medications boost the communication between your nerves and your muscles. They can help strengthen muscles.
  • Corticosteroids. Corticosteroids such as prednisone mute your immune system and slow the release of antibodies that could be helping block your nerve receptors.
  • Immunosuppressants. Your doctor may add immunosuppressants to your corticosteroids to help reduce your immune system response.
  • Neonatal Fc receptor blocker. It works by blocking the autoantibodies that cause myasthenia gravis and helps ease the symptoms.

If you’re dealing with a sudden worsening of symptoms or will soon have surgery or other therapies, your doctor may recommend intravenous (IV) therapy. Choices for this include:

  • Plasmapheresis. This procedure is like dialysis, because it filters your blood. Your blood goes through a machine that removes certain antibodies. The effects are faster than other treatments but they are not long lasting (about a month). This procedure is usually used in a crisis.
  • Intravenous immunoglobulin (IVIg). This therapy injects new antibodies into your bloodstream. These antibodies alter your immune system response to help with symptoms. Results typically last about 3-6 weeks.
  • Monoclonal antibodies. Your doctor will likely recommend this option only if other treatments haven’t worked. They can have serious side effects.

If your myasthenia gravis is due to a tumor on your thymus gland, you may need surgery to remove the whole gland (thymectomy). Even if you don’t have a tumor, taking your thymus out may help ease your symptoms. It may take years to see benefits from a thymectomy.

You may need open surgery to remove your thymus. A surgeon opens your breastbone to get to your thymus and take it out.

Another option that may work is minimally invasive surgery. There are two options:

  • Video-assisted thymectomy. Surgeons make small cuts in your neck or chest and use a long, thin camera called an endoscope along with instruments to take out your thymus.
  • Robot-assisted thymectomy. Surgeons make the same small cuts as video-assisted thymectomy and then use a robot with a camera and mechanical arms to remove your thymus.

In addition to medical treatments, you can make lifestyle changes to help manage your myasthenia gravis symptoms, including:

  • Save energy when you eat. If chewing is a struggle, eat at times when you have the most strength. You might find it easier to eat several small meals a day instead of longer, larger ones less often. Stick to soft foods, and take breaks between bites.
  • Install safety aids. Put handrails anywhere you might need a helpful handle, like next to the toilet or near tables. Remove any tripping risks such as rugs or floor clutter.
  • Let machines do the work. Switch to an electric toothbrush and can opener, or any other device that can save you strength.
  • Wear an eye patch. It can help with double vision. Use one when you watch TV or read, and switch eyes from time to time.
  • Plan ahead. Be smart with your strength. Do chores or errands when you feel best during the day.