Myasthenia gravis is a rare long-term condition that causes muscle weakness that comes and goes.

It most commonly affects muscles that control the eyes and eyelids, facial expressions, chewing, swallowing and speaking. But it can affect most of the body.

It can affect people of any age, typically starting in women under 40 and men over 60.
Common symptoms of myasthenia gravis include:
  • droopy eyelids
  • double vision
  • difficulty making facial expressions
  • problems with chewing and difficulty swallowing
  • slurred speech
  • weak arms, legs or neck
  • shortness of breath and occasionally serious breathing difficulties

The symptoms tend to get worse when you're tired. Many people find they are worse towards the end of the day, and better the next morning after getting some sleep.

When to see your GP

See your GP if you have long-lasting or worrying symptoms that could be caused by myasthenia gravis.

They will ask about your symptoms and medical history.

If your GP thinks you could have a condtion like myasthenia gravis, they may refer you to a specialist for tests to help diagnose the condition or look for other possible causes of your symptoms.

These tests may include a blood test, a test of how well your nerves are working and some scans.

Treatments for myasthenia gravis

Several treatments are available to help keep the symptoms of myasthenia gravis under control.

These include:

  • avoiding anything that triggers the symptoms - some people find that things such as tiredness and stress make their symptoms worse
  • medication to help improve muscle weakness
  • surgery to remove the thymus gland (a small gland in the chest linked to myasthenia gravis) - read about the causes of myasthenia gravis for more information

If the symptoms get suddenly worse - for example, you develop severe breathing or swallowing difficulties - you may need urgent treatment in hospital.

Outlook for myasthenia gravis

Myasthenia gravis is a long-term condition that typically has phases when it improves and phases when it gets worse.

It usually affects most of the body, spreading from the eyes and face to other areas over weeks, months or years. But in around one in five people, only the eye muscles are affected.

Treatment can usually help keep the symptoms under control so that people who have myasthenia gravis are able to live largely normal, symptom-free lives. Very occasionaly it can get worst in the first two or three years after diagnosis.

Causes of myasthenia gravis

Myasthenia gravis is caused by a problem with the signals sent between nerves and the muscles.

It's an autoimmune condition, which means it's the result of the immune system (the body's natural defence against illness and infection) mistakenly attacking a healthy part of the body.

In myasthenia gravis, the immune system damages the communication system between the nerves and muscles, making the muscles weak and easily tired.

It's not clear why this happens, but it has been linked to issues with the thymus gland (a gland in the chest that's part of the immune system).

In many people with myasthenia gravis, the thymus gland is larger than normal, and in around 1 in 10 people there is abnormal growth of the thymus called a thymona.


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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.

Eyes, eyelids and face

Most people with myasthenia gravis have weakness in the muscles of the eyes, eyelids and face.

This can cause:

  • droopy eyelids - affecting one or both eyes
  • double vision
  • difficulty making facial expressions

In around one in five people, the condition only affects the eye muscles. 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 only had symptoms affecting your eyes for two years or more, it's unusual for other parts of your body to be affected later on.

Swallowing, speaking and breathing

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 "mysathentic crisis".

Call 999 for an ambulance immediately if you have worsening severe breathing or swallowing difficulties, as you may need emergency treatment in hospital.

Limbs and other parts of the body

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.

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Myasthenia gravis can be difficult to diagnose and you may need to have several tests.

First your GP will ask about your medical history and symptoms. Alternatively, your optician may have noticed problems such as double vision or eyelid droop.

If they think you could have a problem with your brain or nerves, they may refer you to a specialist for tests in hospital to help diagnose myasthenia gravis and rule out other conditions with similar symptoms.

Blood test

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 to get worse.

Nerve tests

If the result of your blood test is normal but your 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.

These 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 aren't being caused by a problem in your brain.

Edrophonium test

If it's still not clear what's causing your symptoms, your doctor may recommend a test called an edrophonium test.

The test 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.

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Treatment can help keep the symptoms of myasthenia gravis under control so that you're able to live a largely normal life.

But some people need ongoign treatment, and occasionally emergency treatment in hospital may be necessary if the condition suddenly gets worse.

Avoiding triggers

The symptoms of myasthenia gravis can sometimes have a specific trigger. Doing what you can to avoid your triggers may help.

Common triggers inlcude:

  • tiredness and exhaustion - getting plenty of rest and not over-exerting yourself may help
  • stress
  • 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
  • medicines - make sure your doctor is aware of your condition and get advice before taking anything
  • surgery - make sure your surgeon is aware of your condition before having an operation

It's also a good idea to avoid activities that could be dangerous if you experience sudden weakness, such as swimming alone. If you drive, you should tell the DVLA that you have myasthenia gravis.



The first medicine tried is usually a tablet called pyriodostigmine, which helps electrical signals travel between the nerves and muscles.

It can reduce muscle weakness, but the effect only lasts a few hours so you'll need to take it several times a day. For some people, this is the only medicine they need to control their symptoms.

Possible side effects include stomach cramps, muscle twitching, diarrhoea and feeling sick. Tell your doctor if you get any of these, as they may be able to prescribe other medicines to help with side effects.


If pyriodostigmine doesn't help or only provides short-term relief, your doctor may suggest taking steroid tablets such as prednisolone.

These work by reducing the activity of your immune system (the body's natural defence against illness and infection), to stop it attacking the communication system between the nerves and muscles.

Prednisolone is usually started in hospital if you have problems with swallowing or breathing, or if your symptoms keep getting worse and you need treatment quickly.

You'll usually be advised to take the tablets every other day. You'll normally take a high dose at first, which will be gradually lowered as much as possible once your symptoms are under control.

This is because long-term treatment with steroids can cause unpleasant side effects, such as weight gain, mood swings and an increased risk of getting infections.


If steroids aren't controlling your symptoms, you need to take a high dose of steroids, or steroids cause significant side effects, your doctor may suggest taking a different medicine that reduces the activity of your immune system, such as azathioprine or mycophenolate.

This is taken as tablets every day. It can take at least nine months to take full effect so you will also need to take one of the medicines mentioned above at first.

Side effects can include an increased risk of getting infections, feeling and being sick, loss of appetitie and tiredness. You will also need to have regular blood tests to check the amount of medicine in your body.

If these medicines keep your symptoms under control for a long time (usually years), it may be possible to eventually stop taking them.


Surgery to remove the thymus gland, known as a thymectomy, may sometimes be recommended if you have myasthenia gravis.

This has been shown to improve myasthenia symptoms in some people who have an unusually large thymus (a small gland in the chest), though not in people with a thymus that has grown abnormally (a thymoma).

Symptoms will usually improve in the first few months after surgery, but may keep getting better for up to two years.

Surgery can:

  • reduce the dose of steroids you may need to take
  • reduce the chances of needing to take other immunosuppresants
  • reduce the chances of needing to go into hospital because of worsening myasthenia symptoms for at least three years after surgery

If you have a thymoma, a thymectomy won't usually have much of an effect on your myasthenia symptoms. But surgery to remove your thymus gland will often be recommended because it can cause problems if it's left to keep getting bigger.

Thymectomies are often carried out using keyhole surgery techniques. This involves removing the thymus using special surgical instruments inserted through small cuts (incisions) in the chest.

Emergency treatment in hospital

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 mysathenic crisis, require urgent treatment in hospital.

Treatment may include:

  • oxygen through a face mask
  • 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

Help and support

Living with a rare, long-term condition can be very difficult. Some people find it helpful to get in touch with a local or national support group.

The main UK charity for people with mysathenic gravis and their families is Myaware.

Myaware provides additional useful information about living with myasthenia gravis. The charity also has a Facebook group and local support groups.


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Selected links

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The information on this page has been adapted by NHS Wales from original content supplied by NHS Choices.
Last Updated: 14/06/2017 14:04:55