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Myasthenia Gravis: Symptoms, Causes, Complications & Treatment

A rare neuromuscular disease, myasthenia gravis is a type of disease in which your voluntary muscles become easily tired while carrying out any physical activity. As its name suggests, myasthenia gravis is indeed a 'grave muscle weakness' [1] . It is distinguished by the fatigue and weakness that affect your muscles. The skeletal muscles, that is, the ones used for movement become weak when the communication between nerve cells and muscles become defective. This can restrict your muscles from contracting, therefore resulting in muscle weakness [2] .

The disease is normally mild and does not reduce the life expectancy of the individual affected by it. Myasthenia gravis starts from affecting the muscles around your eyes, causing your eyelids to droop. The condition can cause a restriction in carrying out the daily activities of an individual such as chewing, swallowing, speaking, and breathing [3] .

Although rare, myasthenia gravis is one of the most common disorders linked to neuromuscular transmission. According to the Myasthenia Gravis Foundation of America, the disease affects about 14 to 20 people out of every 100,000 people. Under a global perspective, the disease affects between 36,000 to 60,000 people. Even though it can develop at any age, it commonly occurs amongst women before the age of 40 years, and men after the age of 60 years [4] .

Symptoms Of Myasthenia Gravis

The major sign of the condition is muscle weakness, which worsens with the use of the affected muscles. As proper rest can improve the symptoms, the muscle weakness will not be permanent as it may come and go. However, symptoms of myasthenia gravis tend to worsen over time and reaches the maximum within a few years after the initial onset of the disease [5] .

Each of your skeletal muscles will be affected and can have varying symptoms because the symptom shown by your eyes will differ from that of your throat muscles.

1. Eye muscles

One of the first signs to be developed by individuals with myasthenia gravis is on the eyes. More than half of the people with the disease have eye problems such as [6]

  • Double vision called diplopia, which may be horizontal or vertical, and improves or resolves when one eye is closed.
  • Drooping of one or both eyelids termed as ptosis.

2. Neck and limb muscles

Myasthenia gravis can cause weakness in your legs, arms and neck. This weakness on the limbs is caused along with that of weakness in other parts of your body such as your throat, eyes or face. It affects the limbs on your arms more than that of the limbs in your legs. When it affects your legs, it will cause to waddle while you walk. The symptoms affecting the neck will make it difficult to hold up your head. You will find it difficult to walk up stairs or lift objects [7] .

3. Face and throat muscles

About 15 per cent of people with myasthenia gravis will have symptoms related to their face and throat muscles, initially. These can cause the following [8] [9] :

  • Chewing difficulties as the muscles used for chewing can wear out halfway through a meal. Especially if you are eating food that requires a lot of chewing, like meat.
  • Difficulty swallowing as there is increased chances of choking. The condition can cause you to choke, thereby making it difficult to drink and eat. It can cause the liquid you are drinking to come out through your nose as well.
  • Altered speaking as the condition can cause your speech to be very soft or nasal, depending on the muscles which are affected.
  • Limited facial expressions as it can affect the muscles that control your facial expressions.

*It has to be noted that not every individual will have the same symptoms, an also the severity of muscle weakness can vary each day and mostly tend to increase with time.

When To See A Doctor

You must visit a doctor immediately if you are facing difficulty in carrying out the following actions [10] .

  • Using your arms or hands
  • Swallowing
  • Breathing
  • Holding up your head
  • Seeing
  • Walking
  • Chewing

Causes Of Myasthenia Gravis

The disease is caused due to an autoimmune problem which occurs when your immune system mistakenly attacks the healthy tissue [11] [12] [13] .

1. Antibodies

For an individual suffering from myasthenia gravis, the antibodies (proteins) which are usually supposed to attack the foreign, harmful substances in the body will attack the neuromuscular junction. This damages the neuromuscular membrane, thereby reducing the effect of the neurotransmitter substance acetylcholine (a critical substance required for communication between nerve cells and muscles). As the antibodies block the function of the protein, it will lead to the development of myasthenia gravis.

2. Thymus gland

According to it some studies, it has been pointed out that the gland which is a part of the immune system can trigger as well as maintain the production of antibodies that block acetylcholine. The thymus gland is large in infancy and becomes smaller as one age. However, in adults with myasthenia gravis, the gland is abnormally large.

3. Other causes

In some people, myasthenia gravis is not caused by the antibodies blocking acetylcholine and is termed as antibody-negative myasthenia gravis. It is caused by antibodies that destroy the protein lipoprotein-related protein 4.

Genetic factors are also linked with the development of the condition. Rare cases have been reported where mothers with myasthenia gravis have children who are born with myasthenia gravis, which is also called as neonatal myasthenia gravis [14] .

Risk Factors Of Myasthenia Gravis

Certain factors can worsen the symptoms of the condition. The risk factors pertaining to myasthenia gravis are as follows [15] :

  • Stress
  • Illness
  • Fatigue
  • Some medications such as beta blockers, quinidine gluconate, quinidine sulfate, quinine, phenytoin, and certain anaesthetics and antibiotics

Complications Of Myasthenia Gravis

Though treatable, some of the complications pertaining to the condition have been deemed life-threatening [16] [17] .

1. Thymus tumours

Studies have revealed that about 15 per cent of individuals suffering from myasthenia gravis have a tumour in their thymus. The tumours are termed as thymomas and most are not cancerous.

2. Myasthenic crisis

A life-threatening condition, this occurs to people when their muscles that control the breathing becomes weak and thus, fails to function. If a person is suffering from the myasthenic crisis, emergency treatment is required so as to assist their breathing.

3. Other complications

Individuals suffering from the condition can develop complications such as underactive or overactive thyroid. If the thyroid is underactive, you may develop difficulties dealing with cold, weight gain and other issues. Likewise, if your thyroid is overactive, it can cause difficulties dealing with heat, weight loss etc. Apart from this, they can also develop autoimmune conditions such as rheumatoid arthritis or lupus.

Diagnosis Of Myasthenia Gravis

In order to understand and examine your condition, the doctor will first review your symptoms and medical history. Then, the doctor will carry out a physical examination, and the following tests will be carried out [18] [19] [20] .

1. Neurological examination

Under this, the doctor will examine your neurological health by testing your reflexes, muscle strength, muscle tone, senses of touch and sight, coordination and balance. The neurological examination will test sensation in different areas of your body, as well as the motor functions, like touching your finger to your nose so as to understand if muscle weakness is there.

2. Ice pack test

Your doctor can conduct an ice pack test if you have a droopy eyelid. Under this test, the doctor will place a bag filled with ice on your eyelid. After a short span of two minutes, the doctor will remove the bag and analyse your droopy eyelid for any signs of improvement.

3. Edrophonium test

Under this test, the doctor will inject a chemical called edrophonium chloride. This is done so as to understand whether the muscle weakness is caused as a result of myasthenia gravis. If there is an improvement in your muscle movements, the doctor may conclude that the individual has myasthenia gravis.

4. Repetitive nerve stimulation

A nerve conduction study, this involves the doctors attaching the electrodes to your skin over the muscles so as to carry out the test. Small pulses of electricity will be sent through the electrodes in order to measure the nerve's ability to send a signal to the muscles.

5. Blood analysis

Carrying out a blood test will help understand the doctor if there are any abnormal antibodies present, that can disrupt the receptor sites (where the nerve impulses signal the muscles to move).

6. Single-fibre electromyography (EMG)

This method will measure the electrical activity travelling between your brain and muscles. EMG involves inserting a thin wire electrode through the skin and into a muscle, so as to test a single muscle fibre.

7. Pulmonary function tests

This test is carried out by your doctor to examine whether your condition is affecting your breathing.

Treatment For Myasthenia Gravis

As there is no significant cure for the condition, the goal is to manage and control the symptoms [21] [22] .

1. Medications

Your doctor will prescribe medications (cholinesterase inhibitors) such as pyridostigmine so as to improve the communication between your nerves and muscles. Corticosteroids such as prednisone will help in protecting the immune system by limiting the production of antibodies. Immunosuppressants such as azathioprine, mycophenolate mofetil, cyclosporine, methotrexate or tacrolimus will be prescribed to improve your immune system.

However, prolonged use of these medications can cause side effects such as gastrointestinal upset, nausea, and excessive salivation, sweating (cholinesterase inhibitors), bone thinning, weight gain, diabetes and increased risk of infections (corticosteroids), and vomiting, gastrointestinal upset, nausea, liver damage, increased risk of infection, and kidney damage (immunosuppressants).

2. Intravenous therapy

Under this, various procedures such as plasmapheresis, intravenous immunoglobulin (IVIg) and monoclonal antibody will be carried out. Plasmapheresis is similar to dialysis and helps in removing the antibodies that block transmission of signals. This will help the doctors in gaining access to your veins. IVIg and monoclonal antibody help in altering your immune system and thereby improving the symptoms pertaining to myasthenia gravis.

IVIg has certain mild side effects such as chills, dizziness, headaches and fluid retention.

3. Surgery

As aforementioned, about 15 per cent of people with myasthenia gravis have a tumour in the thymus gland (a gland under the breastbone that is involved with the immune system). If there is no tumour in the thymus gland, the surgery will help in improving your myasthenia gravis symptoms and help eliminate the symptoms. This can help you in stopping the medications.

The surgeries involved in the process are video-assisted thymectomy and robot-assisted thymectomy. These surgery methods in comparison to other methods are easy and better because it includes less blood loss, less pain, lower mortality rates and shorter hospital stay [23] .

*The treatment method suitable for you will be decided by your doctor. Certain factors such as your age, severity of your condition, the location of the muscles affected and other existing medical conditions have to be taken into consideration before finalising on the treatment method [24] .

Lifestyle Changes And Home Remedies

Along with the medications prescribed for the condition, doctors advise that it is beneficial to take up measures which will help in dealing with the symptoms[25] .

Wear an eye patch: If you have double vision, the best measure is to wear an eye patch as it can help relieve the problem. Wear the patch while you write, read or watch television. Also, switch the eye patch to the other eye to help reduce the strain on your eyes, periodically.

Use safety precautions at home: Install support measures such as grab bars or railings in places around your house where you may need support (bathrooms, staircase). Keep your sidewalks and paths outside home clear of dried leaves or dirt, or any sort of debris that can cause a fall.

Adjust your eating routine: Try consuming food when you have muscle strength. Chew your food slowly, and take breaks in between. It is better to eat small meals and incorporate soft foods into your diet.

Use electric appliances and power tools: This will help you in reducing the time taken to cook or wash. Using appliances like an electric toothbrush can make your daily tasks easier [26] .

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Story first published: Sunday, March 10, 2019, 10:18 [IST]