Myasthenia Gravis

Myasthenia gravis is a neuromuscular disorder in which any of your voluntary muscles tire rapidly and get progressively weaker as time goes on. Myasthenia gravis, an autoimmune disorder, is caused by a breakdown in the normal communication between nerves and muscles.

The more you use an affected muscle, the weaker it gets; symptoms usually improve with rest and the weakness may come and go. The muscle groups most likely to be affected include eyes, face and throat and neck and limbs.
  • The eye muscles are usually the first ones to be affected; you may experience drooping in one or both eyelids and double vision.
  • The symptoms that appear in your face and throat muscles include a change in speech (becomes softer or more nasal) or slurred speech.
  • In others, trouble with swallowing and chewing and limited ability to make facial expressions  may be the first signs of MG.
  • Weakness in your neck, arms and legs can make it difficult to hold up your head, lift your arms or walk.

Muscle weakness in MG has a specific cause: changes in the activity of the nerve endings that respond to acetylcholine, which is a neurotransmitter that sends messages between cells. Acetylcholine activity is blocked by many commercial insecticides (insects are more susceptible than people). In some patients with MG, autoantibodies may also affect a muscle-specific tyrosine kinasereceptor that transmits signals within a cell rather than between cells. The autoantibodies that cause MG can result from inappropriate activity of the thymus gland, an organ that is involved in developing the immune response in children and that decreases in size and activity in adults.

Fatigue, illness, extreme heat and stress can worsen myasthenia gravis, as can medications such as beta blockers, quinidine and quinine compounds, phenytoin and certain anesthetics and antibiotics. People with myasthenia gravis can experience a condition known as myasthenic crisis; this is when the muscles that control breathing are too weak to function properly. Emergency assistance with mechanical breathing is needed at this point and medications and blood filtering (for excessive antibodies) can help a person in crisis start to breathe on their own.

Myasthenia gravis can affect people at any age, but it is more common in women younger than 40 and men older than 60. Genetic factors can influence myasthenia gravis; mothers with the condition occasionally have children who are born with it (although if treated as soon after birth, children usually recover). There is no cure for the condition; treatment is designed to help relieve the symptoms.

If you have the condition, there is a relatively small chance you could develop a non-cancerous tumor in your thymus gland (about 15 percent). You may also have an over- or underactive thyroid which can cause difficulties in dealing with temperature extremes or weight control. Autoimmune conditions like rheumatoid arthritis or lupus are more prevalent in someone with myasthenia gravis.

Diagnosis  of Myasthenia Gravis 
To diagnose your condition, our team will review your symptoms and medical history and conduct a physical examination that may include a neurological examination to test reflexes, muscle strength and tone, sense of touch and sight, coordination and balance. We will determine whether your muscle fatigue improves with rest. 

Diagnosis involves several different tests:
  • Injection with edrophonium chloride, a chemical which breaks down acetylcholine (a sudden but temporary improvement in strength as an indication that you have MG) 
  • If you have a droopy eyelid, a bag of ice on your eye for two minutes may result in signs of improvement suggesting MG
  • A blood analysis (abnormal level of antibodies or MG-specific antibodies)
  • Electromyography (EMG) uses electrodes attached to your skin to measure the nerves’ ability to send signals to your muscles; we will do this test several times to see if the ability reduces with fatigue
  • Single-fiber EMG  where we insert a fine wire electrode through the skin into the muscle to measure the electrical activity of a single muscle fiber

We may also recommend other tests:
  • Imaging scans to detect tumors or other abnormalities
  • Pulmonary function test to determine if your condition is affecting your breathing

Treatment Options  for Myasthenia Gravis 

Our  team will use a combination of multiple treatments — medications, therapy, surgery and lifestyle changes — to relieve your symptoms of myasthenia gravis. Your treatment plan will depend on several factors, including age, the severity of your condition, the location of the affected muscles and other existing medical conditions.
  • Some of the medications we will recommend include cholinesterase inhibitors (pyridostigmine) to increase communication between nerves and muscles, corticosteroids (prednisone) to limit antibody production and immunosuppressing drugs (azathioprine) to alter your immune system response.
  • We will offer several therapies to help alleviate your symptoms, including plasmapheresis to filter antibodies out of your blood and intravenous immunoglobulin (IVIg) to introduce normal antibodies into your blood.
  • Surgery to remove your thymus gland may improve your symptoms, but it could take years for you to see the results.
  • We will recommend several things to try at home to improve the quality of your life, such as eating several smaller meals a day when your strength is good, eating softer foods that require less chewing, installing grab bars around your home to reduce falling mishaps, using power tools and appliances instead of doing tasks by hand, wearing an eye patch to relieve double vision and planning your errands and chores for when you have the most strength.


Our physicians at Houston Methodist specialize in managing myasthenia gravis at the following convenient locations.