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What is Myasthenia Gravis (MG)?

Home  /  Health Conditions   /  What is Myasthenia Gravis (MG)?
myasthenia gravis

What is Myasthenia Gravis (MG)?

Myasthenia gravis definition says that it is a chronically occurring neuromuscular, autoimmune disorder in which weakness occurs in the skeletal muscles. Autoimmune disorder means that the immune system itself attacks the body’s receptors. The associated weakness exacerbates after activity and improves after rest. The skeletal muscles have a role in breathing and the movement of body parts that include arms and legs.

The term ‘Myasthenia Gravis has both Greek and Latin origins, means’ serious or grave muscle weakness.’ Although no curative remedy has been found for this autoimmune disease, existing treatments have made myasthenia gravis manageable. With the current therapies, the symptoms of the disorder can be controlled, allowing patients to lead an improved quality of life.

 

Causes of Myasthenia Gravis

 

Antibodies

Neurotransmitters are chemicals released by nerves to communicate with the muscles. These neurotransmitters precisely attach into receptors over the muscle cells at the nerve-muscle junction.

Your immune system makes your antibodies and damage or block several receptor sites of your muscles. However, the question arises, myasthenia gravis occurs when antibodies attack which receptor sites?

Antibodies corresponding to the receptors of the neurotransmitter acetylcholine can lead to the condition. As very few receptor sites are available, fewer nerve signals are received by your muscles that lead to weakness.

Antibodies may also restrict the activity of a protein called muscle-specific receptor tyrosine kinase, also called MuSK. It is responsible for the formation of the nerve-muscle junction. When antibodies attack this protein, it can cause MG disease.

Moreover, when antibodies work against a protein, lipoprotein-related protein 4 (LRP4), it may also lead to this disorder. Studies have shown other antibodies to be involved as causative factors of the gravis disease, and their number is expected to rise.

However, in some patients, myasthenia gravis doesn’t develop due to antibodies blocking acetylcholine, LRP4, or MuSK. This kind of condition is known as antibody-negative or seronegative myasthenia gravis. Nonetheless, it is assumed that while this type doesn’t seem to involve antibodies, it still has an autoimmune basis.

 

Thymus gland disorders

The thymus gland can be found underneath the breastbone in the upper chest region as part of your immune system. It is believed by researchers that the thymus gland activates or mediates antibody production, which blocks acetylcholine.

The thymus gland is large in size in infants, and its size reduces with age, becoming small in healthy adults. However, in some people with myasthenia gravis, its size becomes abnormally large. Certain patients of MG disease can also have thymus gland tumors called thymomas.

 

Other causes

Rarely are children born with myasthenia gravis, called neonatal myasthenia gravis. However, those who have it typically get well within 2 months after birth.

  • Illness Or Infection
  • Fatigue
  • Stress
  • Surgery
  • Medications —beta-blockers, Quinidine Sulfate, Quinidine Gluconate, Quinine (Qualaquin), Phenytoin, Some Anesthetics, And Antibiotics
  • Menstrual Periods
  • Pregnancy

 

What Are The Symptoms Of Myasthenia Gravis?

The primary symptom of Myasthenia Gravis includes weakness of voluntary muscles, which are muscles under your control. Muscles may fail to contract generally due to their inability to respond to nerve impulses. Because of the lack of impulse transmission, blockage occurs in the communication between muscles and nerves, resulting in weakness. This weakness generally worsens with activity and improves with rest. 

 

Other Symptoms Of Mg Disease Can Include:

  • Fatigue
  • Hoarse Voice
  • Trouble Talking
  • Difficulty Climbing The Stairs Or Lifting Objects
  • Facial Paralysis
  • Problems In Breathing Because Of Muscle Weakness
  • Difficulty Chewing
  • Double Vision
  • Drooping Of Eyelids

 

However, all symptoms might not necessarily be present in every patient, and the severity of muscle weakness may vary from day to day. If not treated in time, the degree of the symptoms becomes serious with time.

 

 

Complications

While the complications of myasthenia gravis are manageable, some of them can be lethal. These include the following.

 

Myasthenic Crisis

The weakening of the muscles that control breathing leads to a complication called Myasthenic Crisis. It is a life-threatening complication that happens due to the extreme fragility of these muscles. In such cases, emergency intervention along with mechanical support for breathing is required. Patients can start breathing on their own again, with medicines and blood-filtering treatments.

 

Thymus Gland Tumors

In some patients, myasthenia gravis disease occurs due to a thymus gland tumor (thymoma). Although the majority of these tumors are not malignant i.e., they do not spread throughout the body but negatively impact the immune system.

 

Other Disorders

Individuals who have myasthenia gravis are more susceptible to have certain other disorders, which include:

  • Overactive Or Underactive Thyroid. The thyroid gland, situated in the anterior part of your neck, has a key role in secreting thyroid hormone, regulating your metabolism. An underactive thyroid might cause problems, including feeling cold, weight gain, etc., while the overactive thyroid may cause problems with feeling excessive heat, weight loss, etc.
  • Autoimmune Conditions.  Individuals who have myasthenia gravis may be more prone to have autoimmune conditions, for example, lupus or rheumatoid arthritis.

 

 

How is Myasthenia Gravis Diagnosed?

Your clinician will suggest various tests for the confirmation of myasthenia gravis diagnosis.

 

Tests

Physical and neurological examination

Your clinician will review medical history and carry out a physical examination. A neurological examination will include checking muscle tone and strength, coordination, sense of touch, and looking for eye movement issues.

 

Edrophonium Test

Edrophonium chloride injections are used to concisely alleviate weakness myasthenia gravis patients. It obstructs acetylcholine breakdown and briefly elevates acetylcholine levels at the neuromuscular junction. Generally, it is used to test weakness of ocular muscles.

 

Blood Test 

Blood tests are done to check for the elevated levels of certain antibodies in the blood, including acetylcholine receptor antibodies and anti-MuSK antibodies. However, some people with myasthenia gravis may be negative for these antibodies. They may have the seronegative type of myasthenia gravis.

 

Electrodiagnostics

Repetitive nerve stimulation may also be needed to check for the stimulation of the patient’s nerves with the help of small electric pulses that exhaust certain muscles. In patients with MG disease and with other neuromuscular disorders, muscles don’t respond to repetitive electrical stimulation as well as in muscles from healthy individuals. The most sensitive test for gravis disease is Single Fiber Electromyography (EMG), which perceives diminished nerve-to-muscle transmission. This test can help to diagnose mild cases of MG when other tests do not successfully demonstrate abnormalities. 

 

Diagnostic Imaging

Magnetic resonance imaging (MRI) or Computed tomography (CT) of the chest can be used for the identification of a thymoma.

 

Pulmonary Function Testing

Respiratory failure can be checked by measuring breathing strength and may cause a myasthenic crisis.

As weakness is a commonly occurring symptom of several disorders, myasthenia gravis diagnosis can be delayed or missed in individuals with mild weakness or in those who have weakness locally in a few muscles.

 

 

Treatment of Myasthenia Gravis

Several single or combination treatments may alleviate symptoms of myasthenia gravis. The treatment you will get also depends on your age, the severity of your disorder, and how it is progressing.

 

Medications

Cholinesterase Inhibitors

Medicines, including pyridostigmine, are used to improve communication between muscles and nerves. These medicines do not cure the condition but can enhance muscle strength and contraction in some patients. Their side effects can include diarrhea, gastrointestinal upset, nausea, and extreme sweating and salivation.

 

Corticosteroids

Prednisone obstructs the immune system and limits the production of antibodies. However, long-term corticosteroid use can lead to severe side effects, including weight gain, bone thinning, diabetes, and an amplified risk of infections.

 

Immunosuppressants

You might also get other medicines prescribed by your doctor, which regulates your immune system, including azathioprine, mycophenolate mofetil, cyclosporine, methotrexate, or tacrolimus. Adverse effects of immunosuppressants include elevated risk of infection and kidney or liver damage.

 

Intravenous Therapy

Intravenous therapy may also be used for myasthenia gravis treatment for the short-term for the treatment of rapid deterioration of symptoms or prior to surgery.

Plasmapheresis

In this process, a filtering procedure is used that is similar to dialysis. Blood is passed through a machine that eliminates the antibodies that obstruct signal transmission from the nerve endings to muscles’ receptor sites. The risks related to plasmapheresis are a decrease in blood pressure, heart rhythm problems, bleeding, or muscle cramps. Some individuals may develop an allergic reaction due to the compounds found in the replacement of the plasma.

 

Intravenous Immunoglobulin (IVIg)

Your body gets normal antibodies with this treatment that plays a role in altering your immune response. Its merits generally become obvious within a week and may last for 3-6 weeks. Its side effects are typically mild and can include dizziness, chills, fluid retention, and headaches.

 

Monoclonal Antibody

The recently accepted eculizumab and Rituximab are intravenous medicines for myasthenia gravis. These medicines are generally utilized in people who are unresponsive to other treatments. They may also have severe side effects.

 

Surgery

Some individuals with gravis disease may have a thymus gland tumor. In such a case, thymectomy will be performed, i.e., surgical removal of thymus gland doctors.

Even in the absence of a thymus gland tumor, thymectomy may improve myasthenia gravis symptoms. Nonetheless, thymectomy benefits may take some years to progress.

Thymectomy procedure involves open or minimally invasive surgery. The open surgery procedure involves the splitting of the sternum (central breastbone) for opening your chest and get rid of the thymus gland.

 

Types

Video-assisted Thymectomy

Either a small incision is placed on your neck, or a few small incisions are made on the side of the chest. A long, thin camera called a video endoscope is used to visualize and remove the thymus gland.

 

Robot-assisted Thymectomy

Small incisions are placed on the side of your chest for the removal of the thymus gland with the help of a robotic system that comprises a camera arm as well as mechanical arms.

Minimally invasive procedures may cause less pain, less blood loss, lower fatality rate, and shorter hospital stays as opposed to open surgery.

 

Lifestyle And Home Remedies

You should adopt an improved lifestyle for utilizing most of your energy and coping with the symptoms of myasthenia gravis.

 

Adopt The Right Eating Routine

Chew your food properly and take your meal during good muscle strength. Try to take breaks between bites. Taking smaller portions of meals a couple of times a day might also help. In addition, eating soft foods and avoiding hard foods that need more chewing can also help.

 

Practice Safety Precautions At Home

Try to prevent falls by installing railings or grab bars in areas where support is needed, including next to the stairs or bathtub. Your floors should be kept tidy, and the area under the rugs should be clean. Moreover, keep your sidewalks and driveways clear of snow, leaves, and other rubble that may cause you to trip.

 

Utilize Electric Appliances And Tools

For maintaining your energy, use electric can openers, electric toothbrushes, and other electrical appliances for performing tasks.

 

Wear An Eye Patch

Eye patches can help alleviate double vision. Wear an eye patch, especially when writing, reading, or watching TV. Also, you should shift the eye patch to the other eye periodically to reduce eyestrain.

 

Plan

Shopping or other tasks should be planned when you have the most energy.

 

 

Coping And Support

Living with myasthenia gravis can be challenging as it turns the body against itself. It can be worsened due to stress, so you should find methods to relax. Never shy to ask for help when needed.

This article is a comprehensive guide that helps you understand your condition and how it progresses. This way, you can help yourself or a loved one suffering from MG disease.

 

 

References

  1.       Anonymous. Myasthenia Gravis. John Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/myasthenia-gravis
  2.       Mayoclinic staff. Myasthenia Gravis. Mayoclinic. Jun 2021. https://www.mayoclinic.org/diseases-conditions/myasthenia-gravis/symptoms-causes/syc-20352036
  3.       NIH Staff. Myasthenia Gravis Fact Sheet. NIH. Apr 2020. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Myasthenia-Gravis-Fact-Sheet+
  4.       Weatherspoon D. Myasthenia Gravis. Healthline. Sept 2018. https://www.healthline.com/health/myasthenia-gravis