Myasthenia Gravis: Causes, Symptoms and Diagnosis
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Myasthenia Gravis

Myasthenia Gravis

Highlights

  1. MG is rare and only affects 14 to 20 people out of every 100,000.
  2. Treatment for MG consists of symptom management.
  3. MG typically occurs in individuals over the age of 40.

Myasthenia gravis (MG) is a neuromuscular disorder that causes weakness in the skeletal muscles, which are the muscles your body uses for movement. It occurs when communication between nerve cells and muscles becomes impaired. This impairment prevents crucial muscle contractions from occurring, resulting in muscle weakness. According to the Myasthenia Gravis Foundation of America, MG is the most common primary disorder of neuromuscular transmission. It’s a relatively rare condition that affects between 14 and 20 out of every 100,000 people in the United States.

What Are the Symptoms of Myasthenia Gravis?

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The main symptom of MG is weakness in the voluntary skeletal muscles, which are muscles under your control. The failure of muscles to contract normally occurs because they can’t respond to nerve impulses. Without proper transmission of the impulse, a blocked communication occurs between nerve and muscle and weakness results.

Weakness associated with MG typically gets worse with more activity and improves with rest. Symptoms of MG can include:

  • trouble talking
  • problems walking up stairs or lifting objects
  • facial paralysis
  • difficulty breathing because of muscle weakness
  • difficulty swallowing or chewing
  • fatigue
  • hoarse voice
  • drooping of eyelids
  • double vision

Not everyone will have every symptom, and the degree of muscle weakness can change from day to day. The severity of the symptoms typically increases over time if left untreated.

What Causes Myasthenia Gravis?

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MG is a neuromuscular disorder that’s usually caused by an autoimmune problem. Autoimmune disorders occur when your immune system mistakenly attacks healthy tissue. In this condition, antibodies, which are proteins that normally attack foreign, harmful substances in the body, attack the neurotransmitter substance acetylcholine, which is a crucial substance for communication between nerve cells and muscles. This results in muscle weakness.

The exact cause of this autoimmune reaction is unclear to scientists. According to the Muscular Dystrophy Association, one theory is that certain viral or bacterial proteins may prompt the body to attack acetylcholine.

According to the National Institutes of Health, MG typically occurs in people over the age of 40. Women are more likely to be diagnosed as younger adults, whereas men are more likely to be diagnosed at 60 or older.

How Is Myasthenia Gravis Diagnosed?

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Your doctor will perform a complete physical exam, as well as take a detailed history of your symptoms. They’ll also do a neurological exam. This may consist of:

  • checking your reflexes
  • looking for muscle weakness
  • checking for muscle tone
  • making certain your eyes move properly
  • testing sensation in different areas of your body
  • testing motor functions, like touching your finger to your nose

Other tests that can help your doctor diagnose the condition include:

  • repetitive nerve stimulation test
  • blood testing for antibodies associated with MG
  • edrophonium (Tensilon) test: A drug called Tensilon (or a placebo) is administered intravenously, through a vein, and you’re asked to perform muscle movements under doctor observation
  • imaging of the chest, using CT scans or MRI, to rule out a tumor

Treatment Options for Myasthenia Gravis

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There is no cure for MG. The goal of treatment is to manage symptoms and control the activity of your immune system.

Medication

Corticosteroids and immunosuppressants can be used to suppress the immune system. These medications help minimize the abnormal immune response that occurs in MG.

Additionally, cholinesterase inhibitors, such as pyridostigmine (Mestinon), can be used to increase communication between nerves and muscles.

Thymus Gland Removal

Removal of the thymus gland, which is part of the immune system, may be appropriate for many patients with MG. Once the thymus is removed, patients typically show less muscle weakness.

According to the Myasthenia Gravis Foundation of America, between 10 and 15 percent of people with MG will have a tumor in their thymus. Tumors, even those that are benign, are always removed because they may become cancerous.

Plasma Exchange

Plasmapheresis is also known as a plasma exchange. This process removes harmful antibodies from the blood, which may result in an improvement in muscle strength.

Plasmapheresis is a short-term treatment. The body continues to produce the harmful antibodies and weakness may recur. Plasma exchange is helpful before surgery or during times of extreme MG weakness.

Intravenous Immune Globulin  

Intravenous immune globulin (IVIG) is blood product that comes from donors. It’s used to treat autoimmune MG. Although it’s not entirely known how IVIG works, it affects the creation and function of antibodies.

Lifestyle Changes

There are some things you can do at home to help alleviate symptoms of MG:

  • Get plenty of rest to help minimize muscle weakness.
  • If you’re bothered by double vision, talk to your doctor about whether you should wear an eye patch.
  • Avoid stress and heat exposure, as both can worsen symptoms.

These treatments cannot cure MG. However, you’ll typically see improvements in your symptoms. Some individuals may go into remission, during which treatment is not necessary.

Tell your doctor about any medications or supplements you take. Some drugs can make MG symptoms worse. Before taking any new medication, check with your doctor to ensure it’s safe.

Complications of Myasthenia Gravis

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One of the most dangerous potential complications of MG is myasthenic crisis. This consists of life-threatening muscle weakness that can include breathing problems. Talk with your doctor about your risks. If you start to have trouble breathing or swallowing, call 911 or go to your local emergency room immediately.

Individuals with MG are at a higher risk of developing other autoimmune disorders such as lupus and rheumatoid arthritis.

Long-Term Outlook

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The long-term outlook for MG depends on a lot of factors. Some people will only have mild symptoms. Others may eventually become confined to a wheelchair. Talk to your doctor about what you can do to minimize the severity of your MG. Early and proper treatment can limit disease progression in many people.

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