Myasthenia gravis is a rare long-term condition that causes muscle weakness. It most commonly affects the muscles that control the eyes and eyelids, facial expressions, chewing, swallowing and speaking. But it can affect most parts of the body. It can affect people of any age, typically starting in women under 40 and men over 60.
Myasthenia gravis causes muscle weakness that typically has times when it improves and other times when it gets worse. It often affects the eyes and face first, but usually spreads to other parts of the body over time. The severity of the weakness varies from person to person. It tends to be worse when you’re tired and gets better after resting. In some people, the symptoms can also have a number of other triggers, such as stress, infections and certain medicines. Because other conditions sometimes occur along with myasthenia gravis and can interfere with treatment, your health care provider may order other tests. You may need a CT scan or an MRI to check for a thymoma. You’ll be checked for high blood pressure and glaucoma, and you’ll probably have your blood tested to see if you have thyroid disease, other autoimmune diseases (such as rheumatoid arthritis or systemic lupus erythematosus), diabetes, kidney problems, or any infections.
A close-up of a man with droopy eyelids caused by myasthenia gravis. Most people with myasthenia gravis have weakness in the muscles of the eyes, eyelids and face
This can cause:
- droopy eyelids – affecting 1 or both eyes
- double vision
- difficulty making facial expressions
In around 1 in 5 people, only the eye muscles are affected. This is known as “ocular myasthenia”. But for most people, the weakness spreads to other parts of the body over a few weeks, months or years. If you’ve had symptoms affecting your eyes for 2 years or more, it’s unusual for other parts of your body to be affected later on.
If the weakness affects the muscles in the mouth, throat and chest, it can cause:
- difficulty chewing
- slurred speech
- a husky, quiet or nasal-sounding voice
- difficulty swallowing
- choking and accidentally inhaling bits of food, which can lead to repeated chest infections
- shortness of breath, particularly when lying down or after exercise
Some people with myasthenia gravis also experience severe breathing difficulties, known as a “mysathenic crisis”. Call an ambulance immediately if you have worsening severe breathing or swallowing difficulties, as you may need emergency treatment in hospital.
The weakness caused by myasthenia gravis can also spread to other parts of the body, including the neck, arms and legs.
This can cause:
- difficulty holding the head up
- difficulty with physical tasks, such as lifting, getting up from sitting to standing, climbing stairs, brushing teeth or washing hair
- a waddling walk
- aching muscles after using them
- The weakness tends to be worse in the upper body than in the legs and feet.
The main test for myasthenia gravis is a blood test to look for a type of antibody (produced by the immune system) that stops signals being sent between the nerves and muscles. A high level of these antibodies usually means you have myasthenia gravis. But not everyone with the condition will have a high level of antibodies, particularly if it’s only affecting the eye muscles (ocular myasthenia). The blood test may be repeated at a later date if the result is normal but your symptoms continue or get worse.
If your blood test result is normal but the doctor still thinks you could have myasthenia gravis, they may suggest an electrical test of your nerves and muscles. These tests, known as electromyography, involve inserting very small needles into your muscles to measure the electrical activity in them. The needles are typically inserted around the eyes, in the forehead or possibly in the arms. The electrical recordings can show whether the signals sent from the nerves to the muscles are being disrupted, which may be a sign of myasthenia gravis.
You may also have a CT scan or MRI scan of your chest to check if your thymus gland is bigger than usual or has grown abnormally (a thymoma). The thymus gland is a small gland in the chest that forms part of the immune system. Problems with the gland are closely associated with myasthenia gravis. Sometimes an MRI brain scan may also be carried out to check that your symptoms are not being caused by a problem in your brain.
If it’s still not clear what’s causing your symptoms, the doctor may recommend a test called an edrophonium test. It involves having an injection of a medicine called edrophonium chloride. If you have a sudden but temporary improvement in muscle strength after the injection, it’s likely you have myasthenia gravis. But this test is rarely done these days because there’s a risk it could cause potentially serious side effects, such as a slow heartbeat and breathing problems. It’s only done if absolutely necessary and in a hospital setting where treatment for any side effects is readily available.
The symptoms of myasthenia gravis can sometimes have a specific trigger. Doing what you can to avoid your triggers may help.
Common triggers include:
- tiredness and exhaustion – getting plenty of rest and not overexerting yourself may help
- stress – read some tips to help reduce your stress levels
- infections – you may be advised to have an annual flu jab and the one-off pneumococcal vaccine, but get advice before having a “live” vaccine, such as the shingles vaccine (live vaccines contain viruses or bacteria that have been weakened)
- medicines – make sure your doctor is aware of your condition and get advice before taking anything on the list of medicines that can trigger myasthenia gravis symptoms
- surgery – make sure your surgeon is aware of your condition before having any operation
It’s also a good idea to avoid activities that could be dangerous if you have sudden weakness, such as swimming alone.
Some people with myasthenia gravis have periods where their symptoms get suddenly worse – for example, they may experience severe breathing or swallowing problems. These potentially life-threatening symptoms, known as a mysathenic crisis, require urgent treatment in hospital.
Treatment may include:
- oxygen through a face mask
- using a breathing machine (ventilator)
- intravenous immunoglobulin therapy – a treatment made from donated blood, which improves muscle strength by temporarily changing how your immune system works
- plasmapheresis – where your blood is circulated through a machine that filters out the harmful antibodies that are attacking the communication system between the nerves and muscles.
There is no cure for myasthenia gravis, but it is treated with medications and sometimes surgery. You may be put on a drug called pyridostigmine (Mestinon), that increases the amount of acetylcholine available to stimulate the receptors.
If you continue to have symptoms on pyridostigmine, an immunotherapeutic agent is usually added. These include azathioprine (Imuran), cyclosporine (Neoral), eculizumab (Solaris), efgartigimod alfa-fcab (Vyvgart), mycophenolate (CellCept), and prednisone to suppress the immune system.
In severe cases, you may need to have your blood sent through a special machine that removes the antibody-containing plasma and replaces it with antibody-free plasma. This is called plasmapheresis. You may also be given a preparation called intravenous immunoglobulin (IVIg) through a needle in a vein.
If you have a thymoma, you will need surgery to remove your thymus (thymectomy). In fact, your doctor may recommend that you undergo this surgery even if no tumor is present because removal of the thymus seems to improve symptoms in many patients.
There are no known ways to prevent myasthenia gravis. If you already have the condition, take these steps to avoid an exacerbation:
- Try to prevent infections with careful hygiene and by avoiding sick people.
- Treat infections promptly.
- Do not become overheated or too cold.
- Avoid overexertion.
- Learn effective methods of dealing with stress.