What is myasthenia gravis?
Myasthenia gravis (MG) is an autoimmune disease. In MG, the body's immune system creates antibodies that damage or block nerve signals to receptors on your muscles. This results in muscle weakness because the muscles do not receive the signals to contract (tighten). Muscles anywhere within the body may be affected. Eyelid droop (ptosis) and double vision may occur if the muscles that control the eyelids and eye movements are affected.
How are the nerves and muscles affected in myasthenia gravis?
- When you want to move a muscle, the brain sends a signal through the nerves that go to the muscle.
- At the junction between the nerve and muscle, the nerve ending releases a chemical called acetylcholine (ACh) that travels from the nerve to the muscle. The space between the nerve and the muscle is called the synapse.
- On the muscle side of the synapse, there are receptors that are waiting to detect acetylcholine. When acetylcholine connects with them, the muscle contracts.
- In MG, acetylcholine is released normally, but antibodies produced by the body’s immune system prevent the acetylcholine from reaching the receptors. The muscle may work at first, but the signal weakens quicker than normal and over time repeat movement may result in a gradual increase in weakness. Muscles that are used frequently are most likely to be weak.
How can myasthenia gravis affect me?
Many people with MG only have eye symptoms (“ocular myasthenia gravis”). These patients have weakness of the muscles that open the eyelids and/or the muscles that move the eyes. This weakness results in the lid droop (ptosis) and double vision due to variation in weakness of different eye muscles between the two eyes.
MG can affect other muscles in the body (“generalized myasthenia gravis”). Shortness of breath or difficulty swallowing are more serious symptoms of MG and must be brought to your doctor's attention immediately.
MG does not produce pain or numbness. If pain is present, it may be due to another process, and you should inform your doctor.
Why do I need to see a neuro-ophthalmologist?
A neuro-ophthalmologist specializes in neurological problems related to the eyes and eye movements. They are often involved in diagnosing myasthenia gravis, especially if the eyelids are droopy or if you have double vision.
There are many different ways myasthenia gravis is diagnosed. Your doctor may diagnose you in the clinic, but may order blood tests or other special tests to help confirm the diagnosis.
- A blood test for antibodies can help confirm the diagnosis, but the antibodies are not always detectable, especially if you only have eye symptoms.
- Your doctor may perform tests in the office to see if there is improvement of your eyelid drooping. One example is the ice test, where your doctor places an ice pack on your eyelids for several minutes, then re-examines your eyelids to see if there is any improvement.
- Once you have been diagnosed with myasthenia gravis, your doctor may order additional testing and refer you to a general neurologist for further treatment.
Example of Ice Test
What is my prognosis?
As with other autoimmune diseases, myasthenia gravis tends to come and go. MG produces variable disease that may last for years or indefinitely. Symptoms may suddenly become worse. They may be triggered by some medications. Once the diagnosis of MG is made, patients need to inform all their physicians, particularly if they are ever seen in an Emergency Department or are scheduled for any type of surgery with anesthesia.
How is myasthenia gravis treated?
- Myasthenia gravis can be treated with pyridostigmine (Mestinon), a medication that helps with the symptoms of muscle weakness. Unfortunately, this does not always relieve lid drooping or double vision.
- Steroid medication may also improve muscle function by affecting the immune system’s ability to produce antibodies. Steroids have many side effects. If your immune system needs to be treated long-term, your doctor will help determine whether to use steroids or other medications that affect immune function.
- Occasionally surgery to remove the thymus gland may be effective in treatment of MG. Your doctor may check for thymus enlargement with a chest CT scan.
Is there a cure for myasthenia gravis?
At this time, there is no known cure for myasthenia gravis. However, many patients are able to control their symptoms with medication alone.
What are my chances of developing weakness in muscles other than my eye muscles?
Myasthenia gravis can affect many muscles or only a few muscles, especially the muscles that move the eye and lift the lid. The chance that ocular MG will involve muscles in the rest of your body is decreased after two years, but there is still are risk of other muscles becoming affected. Inform your physician if you develop problems with breathing or swallowing.
I have myasthenia gravis. What if I become pregnant?
If you have myasthenia gravis and become pregnant, please talk with your doctor to make sure that both you and the baby do well. Myasthenia gravis does not increase risk for miscarriage or affect the fetus during pregnancy. Myasthenia gravis can worsen during pregnancy, and during delivery extra care is typically needed. After birth, the baby may have some weakness related to the antibodies in myasthenia gravis that usually gets better on its own. If you notice your baby has difficulty feeding or breathing, please talk with your doctor.
Are there medications that can make myasthenia gravis worse?
There are many medications that may trigger myasthenia gravis symptoms or make myasthenia gravis worse, such as some antibiotics and some blood pressure and cholesterol medications. Please talk with your doctor about your medications. A partial list can be found at: https://myasthenia.org/What-is-MG/MG-Management/Cautionary-Drugs
Copyright © 2019. North American Neuro-Ophthalmology Society. All rights reserved.
This information was developed collaboratively by the Patient Information Committee of the North American Neuro-Ophthalmology Society. This has been written by neuro-ophthalmologists and has been edited, updated, and peer-reviewed by multiple neuro-ophthalmologists. The views expressed in this brochure are of the contributors and not their employers or other organizations. Please note we have made every effort to ensure the content of this is correct at time of publication, but remember that information about the condition and drugs may change. Major revisions are performed on a periodic basis.
This information is produced and made available “as is” without warranty and for informational and educational purposes only and do not constitute, and should not be used as a substitute for, medical advice, diagnosis, or treatment. Patients and other members of the general public should always seek the advice of a physician or other qualified healthcare professional regarding personal health or medical conditions.