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Myasthenia Gravis

Dr. Sandeep Borse
Neurologist

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Myasthenia Gravis is a long-term, autoimmune condition in which the communication between muscles and nerves is impaired due to the production of certain antibodies resulting in voluntary muscle weakness. The term originates from the Latin and Greek words translating to “grave, or serious, muscle weakness.” Individuals Affected by Myasthenia Gravis produce antibodies against acetylcholine receptors (AChR-Ab) or against a protein called muscle-specific tyrosine kinase (MuSK-Ab). This disease affects any individual irrespective of age but is predominantly seen in younger women (second and third decade) and older men (after the fifth decade) of life. Since there is no known cause, the treatment remains evasive. However, with the timely detection and speedy medical management, individuals affected with Myasthenia Gravis can lead more productive lives.[1,2,9]

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Types

Myasthenia Gravis is further subdivided into the following types based on their signs and symptoms.


  • Generalised Myasthenia Gravis- This occurs when weakness occurs in multiple groups of muscles.

  • Ocular Myasthenia Gravis- This occurs when the disease-related muscle weakness is restricted to the muscles of the eyes.

  • Transient neonatal Myasthenia Gravis- This form of the disease mainly occurs when infants are born to mothers affected with myasthenia gravis. The infants show muscle weakness for a few days to a few weeks, after which their normal muscle tone and strength are restored.

  • Seropositive Myasthenia Gravis- Acetylcholine receptor antibodies (AchR-Ab) or MuSk-Ab are positive.

  • Seronegative Myasthenia Gravis- The above antibodies are negative in the blood test. These individuals are more prone to ocular Myasthenia Gravis than individuals affected with seropositive myasthenia gravis.[3,9]

Symptoms

Muscle weakness due to myasthenia gravis can be fluctuating. The reason being with adequate rest the muscles regain some of their vigour.  But repeated usage of the same muscles can lead to worsening of the symptoms and the condition. The muscles of the body which are most affected due to the condition are the eyelid, neck and limb, face and throat, among others. The common symptoms of the condition are:


  • Drooping of one or both eyelids leads to a condition called ptosis.

  • Double vision, which resolves if one eye is closed.

  • Difficulty in swallowing and chewing. The swallowing reflex is lost, and it is difficult to eat or even swallow liquids.

  • Limited expressions. Difficulty in smiling, rigid expressions, if the receptors of facial muscles are malfunctioning.

  • Difficulty in using limbs. Finding it difficult to take a stroll or use of hands can be a more prominent sign of the condition.

  • Breathing difficulty. With the muscles of the face and neck being affected, the condition can also make breathing a problem. This can be a life-threatening symptom, and prompt medical management is required.

  • It is usually seen that the symptoms like muscle weakness become worse during the evening or towards the end of the day. It is observed that muscle weakness improves with rest.[4]

Causes And Risk Factors

Causes


The probable causes of myasthenia gravis are as follows:

  • Nerve-and-muscle transmission defect: The nerves that control the muscles release chemicals called neurotransmitters, which are accepted by the receptors of the muscles. These neurotransmitters send signals to the muscles to work in accordance. With a condition like myasthenia gravis, the immune system of the body produces antibodies that destroy or block the receptors in the muscle. With fewer receptors, the muscles receive fewer signals from the nerves. This results in muscle weakness and fatigue.

  • Thymus gland malfunctioning: The thymus gland is present in the chest area right beneath the breastbone. It is believed that this gland contributes a lot to the development of the body’s immune system. Usually, during infancy, the gland is large in size; it reduces as one grows up and the body’s immune system develops. But with people suffering from myasthenia gravis, the thymus is usually large. Though it is not clear how a large thymus gives rise to the condition, experts believe that an abnormal thymus can send improper signals to the immune cells to develop antibodies that block the muscle receptors.

  • Genetic factors: In some very rare cases, genetic factors can be associated with the condition. Sometimes some people are born with a rare form of the condition called congenital myasthenia syndrome. If a mother suffering from the condition gives birth to a baby with the same, the condition is usually treatable within two months after birth.


Risk Factors


The risk factors for myasthenia gravis are as follows.

  • Any autoimmune diseases which run in the family.

  • Men> 60 years of age

  • Women < 40 years of age.[5]

Prevention

There is no definite method of preventing myasthenia gravis, as the cause for it is unknown. However, there are certain ways to prevent symptoms from worsening or flaring up, once an individual is diagnosed with myasthenia gravis. These preventive measures are as follows:


  • Interspace your work well to include enough rest periods.

  • Avoid exposure to extreme temperature variations like extreme heat or extreme cold.

  • Avoid situations that lead to your emotional or physical stress.

  • Avoid exposure to infected individuals. Vaccination against influenza can be helpful.

  • Be attentive to the medications that you are taking. Certain medications prescribed for other ailments like hypertension, and infections could worsen myasthenia gravis symptoms. It is, therefore, best to consult and inform your physician before you start any new medication.[6]

Diagnosis

A diagnosis of the condition is done in the following way:


  • Physical examination: The doctor might ask you to do certain movements to check on the reflexes, muscle strength, muscle tone, coordination and balance.

  • Blood test: A blood test might be done to check for the antibodies available in the body that block the receptors of the muscles.

  • Edrophonium test: In this test, injections are given to check if the muscles gain their strength with the insertion of the chemical edrophonium chloride. This might result in a sudden, although temporary, improvement in muscle strength. This is an indication that you may have myasthenia gravis.

  • Electromyography (EMG): Though a bit uncomfortable, this test involves the insertion of a thin electrode through the skin to the affected muscle to measure the electrical activity between the brain and the muscles

  • Imaging scan: A CT scan or MRI might be done to check if there is a tumour or other abnormality in the thymus.

  • Pulmonary function tests: Certain pulmonary function tests are done to check if the condition affects breathing.

Treatment

There is no cure for the condition, but with proper treatment, the condition can be managed effectively. Following are the treatment options for the same:


  • Medications: Cholinesterase inhibitors are prescribed to enhance the communication between the nerves and the muscles, and improve muscle contraction and strength. The side effects of the drug include gastrointestinal upset, nausea, excessive salivation and sweating. Corticosteroids are at times given to limit antibody production. They too can give rise to side effects with prolonged use like weight gain, diabetes and infections. Sometimes immunosuppressants are given to suppress the production of antibodies. Their side effects can include liver and kidney damage.

  • Surgeries: For people who have tumours developed in the thymus gland, surgical removal is suggested. At times, surgery is recommended even in the absence of tumours to alter the condition’s symptoms. Surgery is usually the last resort of treatment.

  • Plasmapheresis: In this procedure, the plasma of the affected individual is filtered from the irregular antibodies and is swapped with normal antibodies with blood from a donor. It is an expensive, time-consuming, yet lifesaving procedure. Infection, blood clots, and low blood pressure may occur as side effects of this procedure.

  • IVIg: For myasthenia gravis affecting the respiratory muscles, a procedure that intravenously administers a blood product that aids in decreasing the detrimental effects of the antibodies on the immune system is performed.


Further, research is being done to improve the medications for myasthenia gravis treatment, identify novel methods of diagnosing and treating affected individuals and improve treatment opportunities.[2,4]

Lifestyle/management

Certain lifestyle changes might become necessary when you are living with myasthenia gravis. Here are some tips you need to implement.


  1. Plan your day: If you are taking medications, your symptoms might wax and wane during the day. So, finish your chores while you feel a little better. Remember, rest can always help you regain enough muscle strength, so keep some time for rest too.

  2. Be regular with your medications: Because cure is not an option, adhere to your prescriptions for symptom relief. Also, enquire with the treating physician whether taking any other medications could worsen your present condition.

  3. Be careful while walking: Use the sidewalks or pavements when you walk on the roads. At home, keep minimal furniture and less clutter to make movement easy and avoid accidents.

  4. Use electronic appliances: Simple tools can make your life easy and give your muscles enough rest. Using a coffee maker, a dough maker etc. can make it easier for you to work because you reduce your muscles’ exertion.

  5. Follow simple eating techniques: Including mostly soft foods in the diet will help an individual with myasthenia gravis conserve energy. Take smaller portions of food and chew the food properly to avoid getting choked.

  6. Vision problem remedies: In cases of double vision, individuals may be prone to falls and accidents due to disoriented vision. An eye patch on one eye can rectify this double vision issue and help you manage it better.

  7. Stress reduction: Implement stress reduction techniques like yoga and meditation to prevent attacks.

  8. Preventive measure: Avoid the consumption of alcohol. Avoid coming in contact with individuals who are unwell. Wash your hands thoroughly after coming from outside to minimise infections. Also, consider getting an annual shot against the flu.[5]

Prognosis And Complications

Prognosis


With prompt and sustained treatment, muscle weakness can be improved, and individuals with myasthenia gravis can lead almost normal lives. In some cases, remission may occur, in which symptoms completely abate and medications may no longer be required. In around 50% of individuals undergoing surgical interventions like thymectomy, complete remissions may occur.[2]

Complications


A condition like myasthenia gravis can lead to complications like

  • Myasthenic crisis: When the muscles that control breathing are affected, it leads to a crisis situation called myasthenic crisis where artificial ventilation becomes necessary.

  • Thyroid complications: Myasthenia gravis can lead to an underactive or overactive thyroid leading to other health complications.

  • Thymus tumours: Most people suffering from the condition develop tumours in the thymus gland though they are usually benign.

  • Other autoimmune conditions: Untreated myasthenia gravis leads to other conditions like rheumatoid arthritis or lupus.

Alternative Treatments

In a recent study, Chinese herbal medicine was found to be effective in treating symptoms of myasthenia gravis when used as an adjuvant (something that enhances another therapy when used along with it) therapy.[7] 

References



  • Myasthenia Gravis. John Hopkins Medicine Available at: https://www.hopkinsmedicine.org/health/conditions-and-diseases/myasthenia-gravis.

  • Myasthenia Gravis. NIH. Available at: https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Myasthenia-Gravis-Fact-Sheet.

  • Myasthenia Gravis. NORD. Available at: https://rarediseases.org/rare-diseases/myasthenia-gravis/.

  • Myasthenia Gravis. Cleveland Clinic. Available at: https://my.clevelandclinic.org/health/diseases/17252-myasthenia-gravis-mg.

  • Myasthenia Gravis. Intermountain Healthcare Available at: https://intermountainhealthcare.org/ckr-ext/Dcmnt?ncid=529310818.

  • Myasthenia Gravis. Harvard Health Publishing. Available at: https://www.health.harvard.edu/a_to_z/myasthenia-gravis-a-to-z#:~:text=Because%20the%20cause%20of%20myasthenia,Give%20yourself%20plenty%20of%20rest.

  • Myasthenia Gravis. Harvard Health Publishing. Available at: https://www.health.harvard.edu/a_to_z/myasthenia-gravis-a-to-z#:~:text=Because%20the%20cause%20of%20myasthenia,Give%20yourself%20plenty%20of%20rest.

  • Chen,S, et al. Front. Pharmacol. 2018;969(9): 10.3389/fphar.2018.00969

  • Myasthenia Gravis. Muscular Dystrophy Association. Available at: https://www.mda.org/disease/myasthenia-gravis/diagnosis.

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