Myasthenia gravis (MG) is a chronic autoimmune disorder that occurs when the immune system malfunctions, causing the voluntary (skeletal) muscles to become weak. In Latin, myasthenia gravis literally means "grave muscle weakness."
Myasthenia gravis is classified as an autoimmune disorder because the body's immune system, which normally fights against disease and infection, mistakenly attacks the receptors in the body that allow the nerves and muscles to communicate with one another. The cause for this abnormal response is unknown.
Any voluntary muscle may be affected, but the eye muscles, face muscles, and muscles that control breathing and limb movement are most likely to be affected. Most people experience periods of generalized weakness from time to time. Symptoms generally worsen with physical activity and improve with rest.
Although myasthenia gravis can develop at any age, it is most common in women younger than 40 or older than 70 and in men older than 50 years of age. Symptoms may develop suddenly or gradually over time.
It is estimated that myasthenia gravis affects 0.5-14.2 out of 100,000 people in the United States.
In the past, untreated myasthenia gravis led to death in 30-70% of cases. Today, however, patients have normal or near-normal life expectancies. Although there is still no cure for myasthenia gravis, treatment is available to help manage symptoms. The most common causes of death among patients with myasthenia gravis are respiratory failure (when the muscles that control breathing are too weak to function properly), aspiration (the inhalation of food or drink into the lungs) due to an absent or weakened gag reflex, pneumonia, and falls. Also, some of the medications, such as corticosteroids and immunosuppressants, may cause serious side effects, including an increased risk of infections. This is because these medications help alleviate symptoms by reducing the body's immune response.
Because the cause of myasthenia gravis is poorly understood, risk factors have not been clearly defined. The condition can develop at any age, but it is most common in women younger than 40 or older than 70 and in men older than 50 years of age.
Myasthenia gravis occurs when the nerves and muscles in the body are unable to communicate properly. Normally, a chemical called acetylcholine sends nerve signals to the receptor sites of the muscles. The receptor sites then signal the muscles to contract. When the muscles contract, they allow people to perform physical movements. This process is impaired in people with myasthenia gravis.
In people with myasthenia gravis, the immune system, which helps fight against disease and infection, is overactive. For unknown reasons, the immune system attacks the receptor sites for acetylcholine in the muscles, and ultimately blocks, alters, or destroys the receptors. Because the patient has fewer functioning receptor sites than normal, the muscles receive fewer nerve signals, ultimately resulting in muscle weakness.
Researchers believe that part of the immune system, called the thymus gland, may play a role in this autoimmune reaction. It is believed that the thymus gland may trigger and/or produce the abnormal antibodies (called autoantibodies) that attack the receptor sites in the muscles. Some adults with myasthenia gravis have abnormally large thymus glands or tumors on the gland. However, the relationship between the thymus gland and myasthenia gravis is not completely understood.
Several factors may worsen the symptoms of myasthenia gravis, including illnesses or infections, stress, extreme heat, fatigue, and some medications (e.g., quinine, aminoglycoside antibiotics, phenothiazines, methoxyflurane, calcium channel blockers, and beta blockers). Therefore, patients should talk to their doctors before taking any drugs (prescription or over-the-counter), herbs, or supplements.
SIGNS AND SYMPTOMS
General: Although myasthenia gravis can develop at any age, it is most common in women younger than 40 or older than 70 and in men older than 50 years of age. Symptoms may develop suddenly or gradually over 1-2 years. Symptoms tend to worsen with physical activity and improve with rest. Several factors may worsen the symptoms of myasthenia gravis, including illnesses or infections, stress, extreme heat, and some medications (e.g., quinine, aminoglycoside antibiotics, phenothiazines, methoxyflurane, calcium channel blockers, and beta blockers). Symptoms vary considerably among patients. In some patients, weakness may be limited to the eye muscles (a condition called ocular myasthenia gravis) or it may be generalized.
Common symptoms: Symptoms vary depending on the severity and specific muscles that are affected. Myasthenia gravis can affect any voluntary (skeletal) muscle. The most commonly affected muscles include the eye muscles, facial muscles, the arm muscles, the leg muscles, as well as the muscles involved in swallowing, chewing, and talking. The muscles involved in breathing may also be affected. For instance, weakened eye muscles may lead to blurred or double vision, while facial muscle weakness may lead to drooping eyelids, slurred speech/difficulty talking, and difficulty making facial expressions. If the limbs are affected, people may have difficulty walking or performing daily tasks.
Less common symptoms: In rare cases, breathing or swallowing problems may worsen suddenly and require urgent medical treatment.
General: Myasthenia gravis may be suspected if the patient experiences muscle weakness that worsens with physical activity and improves with rest. However, since this is a symptom of many other medical conditions, myasthenia gravis often goes undiagnosed for 1- 2 years after symptoms develop. No single test can confirm a diagnosis. Therefore, if the condition is suspected after a physical examination and detailed medical history, several medical tests, including a neurological examination, blood analysis, edrophonium test, and nerve conduction studies and single-fiber electromyography may be performed to confirm a diagnosis.
Physical and neurological examination: During a physical and neurological exam, a doctor tests the patient's muscle tone and strength, reflexes, gait, coordination and balance, posture, intellectual skills, and senses of sight and touch. The doctor looks for signs of impaired eye movements or muscle weakness without changes in physical sensations.
Blood analysis: A blood test may be performed to determine if the patient has developed autoantibodies, or abnormal antibodies that cause the immune system to attack the receptor sites of the body's muscles. Most patients with myasthenia gravis have elevated levels of autoantibodies. However, these autoantibodies may not be detected if the condition is limited to the eyes (ocular myasthenia gravis).
Edrophonium test: During an edrophonium test, a doctor injects the chemical edrophonium (Tensilon©) into the patient's muscle. If the injection results in a sudden, but temporary improvement in the patient's muscle strength, it may indicate myasthenia gravis. This is because edrophonium blocks an enzyme that breaks down acetylcholine, the chemical that transmits signals from the nerve endings to the muscle receptor sites.
Nerve conduction studies and single-fiber electromyography. During this test, a small electrical impulse is applied to the skin that stimulates the nerves in order to test the strength of the patient's muscle contraction. Then, a needle-electrode is inserted into one of the patient's muscles in order measure the patterns of electrical activity in the muscle when it is at rest compared to contracted.
In rare cases, the respiratory muscles may fail, causing a condition called myasthenic crisis. This condition causes sudden difficulty breathing and requires emergency medical treatment. Some patients may need intensive care and the use of a ventilator. Some factors that may cause myasthenic crisis include stress, infection, fever, or some medications.
General: Although there is currently no cure for myasthenia gravis, treatment is available to help reduce the symptoms. Many lifestyle and self-care techniques, such as wearing eye patches or changes in the diet, may help relieve symptoms. In addition, some medications, such as cholinesterase inhibitors, may be used to improve the communication between the nerves and muscles. Other drugs, such as immunosuppressants, may help limit the amount of abnormal antibodies produced. If the thymus gland is enlarged or there is a tumor on the gland, the thymus gland may need to be surgically removed. These treatments may be used alone or in combination with one another to reduce symptoms.
Patients should tell their doctors if they are taking any medications (prescription or over-the-counter), herbs, or supplements because they may interact with treatment or worsen symptoms of the disorder.
Assisted mobility devices: Some people may require assisted mobility devices from time to time to help them walk. This may include a cane, walker, wheelchair, or mobilized chair. Individuals should talk to their healthcare providers to determine the best options for them.
Diet changes: Eating slowly and resting between bites may help reduce muscle weakness in the face. As a result, this may also help reduce the risk of aspiration. Many doctors recommend that people eat small and frequent meals to avoid fatigue. Soft foods are also recommended because they require less energy to chew. Chewy foods, such as caramel, are discouraged.
Electric appliances: Since physical activity may worsen symptoms of myasthenia gravis, patients may find it beneficial to use electrical appliances, such as electrical toothbrushes and can openers.
Eye patches: Wearing an eye patch from time to time may help reduce eye weakness because symptoms are worsened by physical activity. Some doctors may recommend wearing a single eye patch when reading or watching television and switching it between eyes periodically.
Occupational therapy: Patients may benefit from occupational therapy. These therapists may be able to recommend different ways to perform tasks or certain devices (e.g. Velcro© fasteners) to make daily activities easier. Patients can ask their doctors to recommend therapists.
Cholinesterase inhibitors: Cholinesterase inhibitors, such as pyridostigmine (Mestinon©) and neostigmine (Prostigmin©), may be prescribed to improve the communication between the patient's nerves and muscles. Although these drugs do not treat the underlying problem, they have been shown to improve muscle strength.
Side effects may include, but are not limited to, diarrhea, dizziness, drowsiness, fatigue nausea, and vomiting. People with liver disease, peptic ulcer disease, chronic obstructive pulmonary disease (COPD), and slow heartbeat (bradycardia) should not take these drugs.
Corticosteroids: Oral corticosteroids may also be prescribed. These medications decrease the body's immune response, which limits the amount of antibodies produced. As a result, they may help reduce symptoms of muscle weakness. These medications usually start to reduce symptoms within a few weeks. Once improvement levels off, the dose is slowly decreased. This is because long-term treatment may cause the drugs to become less effective and serious side effects may develop. Side effects may include easy bruising, thinning of bones, cataracts, weight gain, a round face (called moon facies), and diabetes.
Immunosuppressants: Oral immunosuppressants, such as azathioprine (Imuran©), mycophenolate mofetil (CellCept©), cyclophosphamide (Cytoxan©), or cyclosporine (Sandimmune© or Neoral©), may also be prescribed to decrease the body's immune response.
These medications may have serious side effects, including increased risk of infections, kidney problems, high blood pressure, and decreased levels of red blood cells. Other side effects may include increased hair growth, loss of appetite, vomiting, and upset stomach.
Plasmapheresis: A procedure called plasmapheresis has been used to treat life-threatening stages of myasthenia gravis. During plasmapheresis, the patient's blood is filtered through a machine that removes the abnormal antibodies. The blood is then returned to the patient. This therapy is expensive and time consuming.
Intravenous immune globulin (IVIG): Patients may also receive treatment with intravenous immune globulin (IVIG) in order to reduce the number of abnormal antibodies (called autoantibodies) in the blood. Intravenous immune globulin (IVIG) is made of antibodies that have been extracted from blood donations from 3,000-10,000 healthy donors. IVIG is typically administered intravenously for about 2-4 hours daily for 2-7 days. Although this therapy has a lower risk of side effects than plasmapheresis and immunosuppressants, it typically takes about eight days for the patient to start responding to treatment. Also, this therapy is expensive, and it is unclear if this is more effective than other available therapies. Therefore, this treatment is usually only used in people who are severely ill.
Side effects from IVIG occur in fewer than 5% of patients, according to researchers. Common side effects typically occur immediately after infusions and may include flushing (reddening of the cheeks), headache, chills, dizziness, increased sweating, leg cramps, pain and tenderness at the injection site, tiredness, muscle pain, lower back pain, nausea, and low blood pressure.
Surgery: Although it is generally believed that the surgical removal of the thymus gland (called a thymectomy) reduces symptoms in most patients with myasthenia gravis, only about 25% of people who undergo surgery go into remission after one year. Substantial improvements are usually not observed for several years. In addition, recent evidence has brought into question whether or not a thymectomy is effective for people who do not have thymus gland tumors. This surgery is generally recommended for people younger than 60 years of age or for those who have tumors on their glands.
Traditional or theoretical uses lacking sufficient evidence:
Astragalus: In traditional Chinese medicine (TCM), astragalus is commonly found in mixtures with other herbs. In the 1980s, astragalus became highly popular in the United States as an immune system stimulant, and it is one of the most widely purchased herbal remedies today. Although it has been suggested that astragalus may help treat myasthenia gravis, scientific evidence is lacking in this area.
Avoid if allergic to Astragalus membranceous or other members of the Fabaceae family. Use cautiously with weakened immune systems, autoimmune disorders, or if taking immunosuppressants, as astragalus may decrease the effectiveness of immunosuppressants. Use cautiously if taking antivirals. Use cautiously with diabetes or if taking agents that affect blood sugar levels. Use cautiously with high blood pressure or it taking blood pressure-lowering agents. Use cautiously if taking anticoagulants. Use cautiously with kidney or lipid disorders. Avoid if pregnant or breastfeeding due to a lack of safety evidence.
Ephedra: Ephedrine, a constituent of ephedra, has been suggested as a possible treatment for myasthenia gravis. However, because there is a lack of scientific evidence supporting its use, recommendations cannot be made at this time.
Even though ephedra has been suggested as a possible treatment for myasthenia gravis, it is unsafe for humans. Serious reactions, including heart attack, stroke, seizure, and death, have occurred. The U.S. Food and Drug Administration (FDA) banned sales of ephedra dietary supplements in all states except for Utah. Patients should not take ephedrine-containing agents unless recommended by their doctors.
Hypnotherapy, hypnosis: Hypnosis is a trance-like state in which a person becomes more aware and focused and is more open to suggestion. Hypnotherapy has been used to treat health conditions and to change behaviors. It has been suggested, but not scientifically proven, that hypnotherapy may help treat symptoms of myasthenia gravis. Studies are needed to determine if (and how) hypnotherapy can be a useful treatment for these patients.
Use cautiously with mental illnesses (e.g., psychosis/schizophrenia, manic depression, multiple personality disorder, or dissociative disorders) or seizure disorders.
Nux vomica: Nux vomica is the dried, ripe seed of Strychnos nux-vomica, L., a native tree of Burma, China, eastern India, Thailand, and northern Australia. Traditional Asian medicine includes nux vomica as a remedy. Although it has been suggested that nux vomica may help treat symptoms of myasthenia gravis, studies are currently lacking. Until research is performed in humans, it remains unknown if nux vomica is indeed beneficial for this condition.
Avoid if allergic to Strychnos nux-vomica or other members of the Loganiaceae family. Use cautiously as a traditional Asian remedy due to potential toxicity from strychnine in nux vomica. There are reports of poisonous outcomes with traditional use of the seeds or fruit of Strychnos nux-vomica, L. Use cautiously with seizure disorders. Avoid oral doses of nux vomica seeds because the seeds may contain toxic amounts of strychnine. Avoid if pregnant or breastfeeding.
Reishi mushroom: Reishi mushroom (Ganoderma lucidum), also known as ling zhi in China, grows on decaying logs and tree stumps. Reishi occurs in six different colors, but the red variety is most commonly used and commercially cultivated in East Asia and North America. It has been suggested, but not scientifically proven, that reishi mushroom may help treat myasthenia gravis.
Avoid if allergic to reishi mushroom, any of its constituents, or any other member of its family. Use cautiously with diabetes or if taking blood sugar-lowering agents. Avoid with hemophilia. Use cautiously with bleeding disorders or if taking anticoagulants. Use cautiously with hypotension or if taking blood pressure-lowering agents. Use cautiously with gastrointestinal bleeding. Avoid if pregnant or breastfeeding due to a lack of safety evidence.
General: Currently, there is no known method of preventing myasthenia gravis. However, people who develop the disorder can take steps to prevent complications or exacerbations of their conditions.
Avoiding extreme heat: Patients are encouraged to avoid extreme heat because it may worsen symptoms. Cold temperatures do not appear to have this effect.
Discussing medications with physician: Patients are encouraged to tell their doctors if they are taking any drugs (prescription or over-the-counter), herbs, or supplements. This is because some medications (e.g., quinine, aminoglycoside antibiotics, phenothiazines, methoxyflurane, calcium channel blockers, and beta blockers) may worsen symptoms of the disorder.
Proper rest and sleep: Patients are encouraged to get plenty of rest because fatigue may worsen symptoms.
Stress management: People are encouraged to manage stress because stress has been shown to worsen symptoms of myasthenia gravis. People may benefit from time management classes or relaxation or meditative therapies.
Preventing falls: Patients with myasthenia gravis have an increased risk of falling due to muscle weakness. This risk can be reduced by installing grab bars in the shower and near the toilet. A non-slip bath mat can be used in the shower or tub. Proper lighting is also recommended inside the home. Handrails and lights should be installed on the staircases of the home. Consider installing a ramp into the home if there are steps to the front door. Wear rubber-soled slippers that do not slip when walking around the home.
Health support: Patients are encouraged to take steps to prevent infections because symptoms may worsen when a patient is sick. Also, some medications used to treat myasthenia gravis, including immunosuppressants, may weaken the body's immune response, making the patient more susceptible to infections. Limiting contact with others who are sick, frequently washing the hands with soap and warm water, and eating a healthy diet are just some of the ways people can reduce their risks of becoming sick.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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