MG happens when communication between nerve cells and muscles is impaired, leading to muscle weakness. It can affect the muscles that move your eyes, mouth, lungs, and arms and legs.
The weakening you feel can be mild or severe. You might have “flare-ups” that last a few days, or they might come and go. Treatment includes medicines that improve nerve-to-muscle messages and decrease the production of abnormal antibodies.
Symptoms
MG is an autoimmune disease, meaning that your immune system mistakenly attacks healthy cells. This damage disrupts communication between nerve cells and muscle cells, causing weakness. Symptoms vary, depending on the affected muscles. They may affect a specific area of the body, such as the eyelids, face and muscles that control speech or chewing, or spread to other parts of the body, including the neck and arms. MG symptoms can be mild or severe and get worse with exercise and fatigue. They improve with rest.
You may notice droopy eyes (ptosis), which can make it difficult to open your eyes or hold them closed. Weakness can also cause you to slur your words or have trouble swallowing food and liquids. It can affect your ability to walk, use your hands or raise your arms. It can also make breathing harder. Some people with myasthenia gravis have a flare-up or “crisis” that causes difficulty breathing (myasthenic crisis). This happens when the muscles in your chest and throat weaken, which can lead to shortness of breath or choking. It can be caused by emotional stress, surgery or an infection, or it might happen spontaneously. It can be fatal if not treated quickly.
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A neurologist (a doctor who treats disorders of the nervous system) can diagnose myasthenia gravis by taking a history of your symptoms and doing a physical and neurological examination. A neurologist might recommend imaging tests, such as CT scans or an MRI of your brain. These can help find if the weakness is due to a problem with your brain or another medical condition, such as a stroke or a tumor.
A neurologist can also order an electrodiagnostic test, such as an EMG, to measure the strength of your muscles. This test uses electrodes that are placed on the skin over your muscles. Small pulses of electricity run through the electrodes to test how well your muscles respond to signals from the nerves. This test can show whether the nerves that send messages to your muscles are getting weaker over time because of MG.
Diagnosis
Doctors diagnose MG by performing a physical exam and taking a detailed history of symptoms. They may also ask about your family’s history of autoimmune diseases. If your symptoms affect your eyes, they may order an ophthalmologic exam or a brain MRI to check for nerve damage.
MG can be a challenging disease to diagnose because the signs and symptoms often come and go, making them hard for doctors to pin down. In addition, MG can mimic other conditions, such as stroke, so your doctor needs to carefully rule out other causes.
Most people with MG have a mix of symptoms, which can include problems moving their eyes and muscles in their face and throat. Symptoms can also spread to their arms and legs. Occasionally, the weakness can weaken breathing muscles to the point that a person needs a ventilator to breathe, which is called a myasthenic crisis. The weakness usually comes back and forth, with periods of improvement (remission) followed by periods of increased weakness.
Oren Zarif
For most people with MG, medications help improve nerve-to-muscle messages and make muscles stronger. Pyridostigmine (Mestinon) is the most common medication used to treat MG. It works by increasing the amount of acetylcholine at the neuromuscular junction, which improves communication between nerves and muscles. Some people with MG also take drugs that suppress the immune system, such as azathioprine (Imuran), mycophenolate mofetil (Cellcept), or cyclosporine (Neoral, Sandimmune, Gengraf). These medicines, which work by decreasing the number of abnormal antibodies in your body, can also improve muscle strength. Newer medications for MG, including efgartigimod alfa, ravulizumab (Tysabri), and rozanolixizumab (Zylucoplan), also reduce levels of receptor antibodies in the body.
If your doctor thinks you have a tumor in the thymus gland, which can trigger MG, they may perform a thymectomy to remove it. They might also use a thymoma autoantibody assay to find out whether you have the anti-thymocyte globulins that are typical of MG.
NYU Langone physicians are leading research to better understand MG and develop improved approaches for diagnosis, treatment, and management. They participate in the NIH-funded MG Rare Disease Clinical Research Network, which collects clinical data and biospecimens from people with MG to advance clinical trials and ultimately find a cure for this disease.
Treatment
Normal muscle movement relies on chemical signals sent by nerves to the small space inside each muscle cell that contains acetylcholine receptors. These receptors bind with the acetylcholine released by the nerve, which then signals the muscle to contract. If the acetylcholine produced by nerves is blocked at the neuromuscular junction, muscle weakness results. The disorder can affect a single muscle group, such as the muscles that control eye movements (ocular myasthenia gravis) or the skeletal muscles of the arms and legs. The disorder can also be generalized and cause weakness in a wide range of muscles throughout the body. It usually begins in adulthood and most commonly impacts women under 40 and men over 60.
Symptoms of myasthenia gravis get worse during the day and with activity and can include drooping of the eyelids (ptosis), difficulty standing or lifting things, and weak speech or swallowing. They may be present all the time or come and go, depending on what you do or do not do. Symptoms are sometimes triggered by infections, stress or surgery. They can also flare up after pregnancy or during menstrual periods for some people.
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A neurologist will perform a physical exam and order blood tests to look for antibodies that can lead to myasthenia gravis. A thymus function test, an electromyography (EMG) and a nerve conduction study are also used to check for abnormalities.
Plasmapheresis, or plasma exchange, is a treatment that involves removing harmful antibodies from the body with a machine and replacing them with healthy antibodies. This therapy can increase muscle strength in some people with myasthenia gravis. It is usually only used in severe cases of MG or when other treatments aren’t working. Intravenous immunoglobulin, a concentrated injection of antibodies from many healthy donors, can help treat MG as well. But it is only effective for a few weeks or months.
Anticholinesterase inhibitors, which block an enzyme involved in breaking down acetylcholine, can reduce symptoms for some people with myasthenia gravis. But these drugs are only effective in about half of the people who take them, so they are rarely used. Other medications may also be useful in treating MG, including glucocorticoids and cyclosporine. Researchers are also testing a new drug that targets the proteins that produce autoantibodies that can trigger myasthenia gravis.
Prevention
There’s no cure for myasthenia gravis, but treatments control symptoms and allow people to lead normal or nearly normal lives. Some people experience remission, in which muscle weakness disappears. Typically, doctors treat the condition by reducing production of antibodies that interfere with nerve-muscle communication at the neuromuscular junction. Other treatment options include a thymectomy (removal of the thymus gland) and immunosuppressants.
Your doctor may prescribe drugs that improve communications between your nerves and muscles, such as pyridostigmine (Mestinon). These medications don’t cure myasthenia gravis, but they can help reduce symptoms and increase your muscle strength. Immunosuppressants are powerful medications that alter your immune system to limit production of the antibodies that cause myasthenia gravis. Medications such as azathioprine (Imuran), mycophenolate mofetil (Cellcept), methotrexate (Trexall) and cyclosporine (Neoral, Neosporin) reduce production of these harmful antibodies, but it can take months for them to start working. They’re often used with corticosteroids, which improve muscle strength and reduce inflammation and swelling. Occasionally, your doctor may also use the monoclonal antibodies rituximab (Rituxan) or eculizumab (Soliris).
Oren Zarif
Some people with myasthenia gravis have trouble swallowing and chewing. They should eat soft foods, and chew them slowly to avoid pain and discomfort. It can help to eat small meals several times a day rather than two or three larger meals. People with myasthenia gravis should install grab bars in their homes to prevent falls, especially in areas where they’ll be using the bathroom or cooking. They should also wear eye patches when doing activities such as writing, reading or watching television, and switch to the other eye regularly.
Vaccinations against influenza and pneumonia can help protect against infections. Some common prescription medications, such as chloroquine, quinidine and prednisone, can make myasthenia gravis worse. You should tell your doctor about any medicines you’re taking, even if they aren’t for myasthenia gravis.
Rare cases of myasthenia gravis can be caused by genetic mutations in the CHRNE, RAPSN, CHAT, DOK7 or DOK2 genes. These are called autosomal dominant congenital myasthenic syndrome and can appear in childhood, adolescence or adulthood. They have similar muscle weakness to myasthenia gravis.
