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Tuesday, December 18, 2018

Myasthenia Gravis










What is Myasthenia Gravis?

Myasthenia gravis is a chronic autoimmune neuromuscular disease that causes weakness in the skeletal muscles, which are responsible for breathing and moving parts of the body, including the arms and legs. The name myasthenia gravis, which is Latin and Greek in origin, means 'grave, or serious, muscle weakness.'

The hallmark of myasthenia gravis is muscle weakness that worsens after periods of activity and improves after periods of rest. Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often (but not always) involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.

There is no known cure but with current therapies most cases of myasthenia gravis are not as 'grave' as the name implies. Available treatments can control symptoms and often allow people to have a relatively high quality of life. Most individuals with the condition have a normal life expectancy.





What Causes Myasthenia Gravis?

Myasthenia gravis is caused by an error in the transmission of nerve impulses to muscles. It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction—the place where nerve cells connect with the muscles they control.

Neurotransmitters are chemicals that neurons, or brain cells, use to communicate information. Normally when electrical signals or impulses travel down a motor nerve, the nerve endings release a neurotransmitter called acetylcholine. Acetylcholine travels from the nerve ending and binds to acetylcholine receptors on the muscle. The binding of acetylcholine to its receptor activates the muscle and causes a muscle contraction.

In myasthenia gravis, antibodies (immune proteins) block, alter, or destroy the receptors for acetylcholine at the neuromuscular junction, which prevents the muscle from contracting. In most individuals with myasthenia gravis, this is caused by antibodies to the acetylcholine receptor itself. However, antibodies to other proteins, such as MuSK (Muscle-Specific Kinase) protein, can also lead to impaired transmission at the neuromuscular junction.

These antibodies are produced by the body's own immune system. Myasthenia gravis is an autoimmune disease because the immune system—which normally protects the body from foreign organisms—mistakenly attacks itself.

The thymus is a gland that controls immune function and maybe associated with myasthenia gravis. Located in the chest behind the breast bone, the gland is largest in children. It grows gradually until puberty, and then gets smaller and is replaced by fat. Throughout childhood, the thymus plays an important role in the development of the immune system because it is responsible for producing T-lymphocytes or T cells, a specific type of white blood cell that protects the body from viruses and infections.

In many adults with myasthenia gravis, the thymus gland remains large. People with the disease typically have clusters of immune cells in their thymus gland similar to lymphoid hyperplasia—a condition that usually only happens in the spleen and lymph nodes during an active immune response. Some individuals with myasthenia gravis develop thymomas (tumors of the thymus gland). Thymomas are most often harmless, but they can become cancerous.

The thymus gland plays a role in myasthenia gravis, but its function is not fully understood. Scientists believe that the thymus gland may give incorrect instructions to developing immune cells, ultimately causing the immune system to attack its own cells and tissues and produce acetylcholine receptor antibodies—setting the stage for the attack on neuromuscular transmission.




Source: On Image






What are the Symptoms of Myasthenia Gravis?

Although myasthenia gravis may affect any skeletal muscle, muscles that control eye and eyelid movement, facial expression, and swallowing are most frequently affected. The onset of the disorder may be sudden and symptoms often are not immediately recognized as myasthenia gravis.

In most cases, the first noticeable symptom is weakness of the eye muscles. In others, difficulty swallowing and slurred speech may be the first signs. The degree of muscle weakness involved in myasthenia gravis varies greatly among individuals, ranging from a localized form limited to eye muscles (ocular myasthenia), to a severe or generalized form in which many muscles—sometimes including those that control breathing—are affected.



Symptoms may include:

drooping of one or both eyelids (ptosis)
blurred or double vision (diplopia) due to weakness of the muscles that control eye movements
a change in facial expression
difficulty swallowing
shortness of breath
impaired speech (dysarthria)
weakness in the arms, hands, fingers, legs, and neck.





Who gets Myasthenia Gravis?

Myasthenia gravis affects both men and women and occurs across all racial and ethnic groups. It most commonly impacts young adult women (under 40) and older men (over 60), but it can occur at any age, including childhood. Myasthenia gravis is not inherited nor is it contagious. Occasionally, the disease may occur in more than one member of the same family.

Although myasthenia gravis is rarely seen in infants, the fetus may acquire antibodies from a mother affected with myasthenia gravis—a condition called neonatal myasthenia. Generally, neonatal myasthenia gravis is temporary and the child's symptoms usually disappear within two to three months after birth. Rarely, children of a healthy mother may develop congenital myasthenia. This is not an autoimmune disorder (it is caused by defective genes that produce abnormal proteins in the neuromuscular junction) and can cause similar symptoms to myasthenia gravis.




Source:HERE





How is Myasthenia Gravis Diagnosed?


A doctor may perform or order several tests to confirm the diagnosis, including:

A physical and neurological examination. A physician will first review an individual’s medical history and conduct a physical examination. In a neurological examination, the physician will check muscle strength and tone, coordination, sense of touch, and look for impairment of eye movements.

An EDROPHONIUM test. This test uses injections of edrophonium chloride to briefly relieve weakness in people with myasthenia gravis. The drug blocks the breakdown of acetylcholine and temporarily increases the levels of acetylcholine at the neuromuscular junction. It is usually used to test ocular muscle weakness.

A blood test. Most individuals with myasthenia gravis have abnormally elevated levels of acetylcholine receptor antibodies. A second antibody—called the anti-MuSK antibody—has been found in about half of individuals with myasthenia gravis who do not have acetylcholine receptor antibodies. A blood test can also detect this antibody. However, in some individuals with myasthenia gravis, neither of these antibodies is present. These individuals are said to have seronegative (negative antibody) myasthenia.

Electrodiagnostics. Diagnostic tests include repetitive nerve stimulation, which repeatedly stimulates a person’s nerves with small pulses of electricity to tire specific muscles. Muscle fibers in myasthenia gravis, as well as other neuromuscular disorders, do not respond as well to repeated electrical stimulation compared to muscles from normal individuals. Single fiber electromyography (EMG), considered the most sensitive test for myasthenia gravis, detects impaired nerve-to-muscle transmission. EMG can be very helpful in diagnosing mild cases of myasthenia gravis when other tests fail to demonstrate abnormalities.

Diagnostic imaging. Diagnostic imaging of the chest using computed tomography (CT) or magnetic resonance imaging (MRI) may identify the presence of a thymoma.



Source: HERE




Pulmonary function testing. Measuring breathing strength can help predict if respiration may fail and lead to a myasthenic crisis.
Because weakness is a common symptom of many other disorders, the diagnosis of myasthenia gravis is often missed or delayed (sometimes up to two years) in people who experience mild weakness or in those individuals whose weakness is restricted to only a few muscles.




Source: McGraw Hill





What is a Myasthenic Crisis?

A myasthenic crisis is a medical emergency that occurs when the muscles that control breathing weaken to the point where individuals require a ventilator to help them breathe.

Approximately 15 to 20 percent of people with myasthenia gravis experience at least one myasthenic crisis. This condition usually requires immediate medical attention and may be triggered by infection, stress, surgery, or an adverse reaction to medication. However, up to one-half of people may have no obvious cause for their myasthenic crisis. Certain medications have been shown to cause myasthenia gravis. However, sometimes these medications may still be used if it is more important to treat an underlying condition.






How is Myasthenia Gravis Treated?

Today, myasthenia gravis can generally be controlled. There are several therapies available to help reduce and improve muscle weakness.

THYMECTOMY. This operation to remove the thymus gland (which often is abnormal in individuals with myasthenia gravis) can reduce symptoms and may cure some people, possibly by rebalancing the immune system. A recent NINDS-funded study found that thymectomy is beneficial both for people with thymoma and those with no evidence of the tumors. The clinical trial followed 126 people with myasthenia gravis and no visible thymoma and found that the surgery reduced muscle weakness and the need for immunosuppressive drugs.

Anticholinesterase medications
. Medications to treat the disorder include anticholinesterase agents such as MESTINON or PYRIDOSTIGMINE, which slow the breakdown of acetylcholine at the neuromuscular junction and thereby improve neuromuscular transmission and increase muscle strength.

Immunosuppressive drugs. These drugs improve muscle strength by suppressing the production of abnormal antibodies. They include prednisone, azathioprine, mycophenolate mofetil, tacrolimus, and rituximab. The drugs can cause significant side effects and must be carefully monitored by a physician.

Plasmapheresis and intravenous immunoglobulin. These therapies may be options in severe cases of myasthenia gravis. Individuals can have antibodies in their plasma (a liquid component in blood) that attack the neuromuscular junction. These treatments remove the destructive antibodies, although their effectiveness usually only lasts for a few weeks to months.

Plasmapheresis is a procedure using a machine to remove harmful antibodies in plasma and replace them with good plasma or a plasma substitute.
Intravenous immunoglobulin is a highly concentrated injection of antibodies pooled from many healthy donors that temporarily changes the way the immune system operates. It works by binding to the antibodies that cause myasthenia gravis and removing them from circulation.




Source: On Image




What is the prognosis?

With treatment, most individuals with myasthenia can significantly improve their muscle weakness and lead normal or nearly normal lives.

Sometimes the severe weakness of myasthenia gravis may cause respiratory failure, which requires immediate emergency medical care.

Some cases of myasthenia gravis may go into remission—either temporarily or permanently—and muscle weakness may disappear completely so that medications can be discontinued. Stable, long-lasting complete remissions are the goal of thymectomy and may occur in about 50 percent of individuals who undergo this procedure.





What Research is Being Done?

The mission of the National Institute of Neurological Disorders and Stroke (NINDS) is to seek fundamental knowledge about the brain and nervous system and to use that knowledge to reduce the burden of neurological disease. The NINDS is a component of the National Institutes of Health (NIH), the leading supporter of biomedical research in the world.

Although there is no cure for myasthenia gravis, management of the disorder has improved over the past 30 years. There is a greater understanding about the structure and function of the neuromuscular junction, the fundamental aspects of the thymus gland and of autoimmunity, and the disorder itself. Technological advances have led to more timely and accurate diagnosis of myasthenia gravis and new and enhanced therapies have improved treatment options. Researchers are working to develop better medications, identify new ways to diagnose and treat individuals, and improve treatment options.





Medication

Some people with myasthenia gravis do not respond favorably to available treatment options, which usually include long-term suppression of the immune system. New drugs are being tested, either alone or in combination with existing drug therapies, to see if they are effective in treating the disease.

Studies are investigating the use of therapy targeting the B cells that make antibodies (rituximab) or the process by which acetylcholine antibodies injure the neuromuscular junction (eculizumab). The drugs have shown promise in initial clinical trials.






Diagnostics and biomarkers

In addition to developing new medications, researchers are trying to find better ways to diagnose and treat this disorder. For example, NINDS-funded researchers are exploring the assembly and function of connections between nerves and muscle fibers to understand the fundamental processes in neuromuscular development. This research could reveal new therapies for neuromuscular diseases like myasthenia gravis.

Researchers are also exploring better ways to treat myasthenia gravis by developing new tools to diagnose people with undetectable antibodies and identify potential biomarkers (signs that can help diagnose or measure the progression of a disease) to predict an individual’s response to immunosuppressive drugs.





Source: McGraw Hill





New treatment options

Findings from a recent NINDS-supported study yielded conclusive evidence about the benefits of surgery for individuals without thymoma, a subject that had been debated for decades. Researchers hope that this trial will become a model for rigorously testing other treatment options, and that other studies will continue to examine different therapies to see if they are superior to standard care options.






Where can I get more information?

For more information on neurological disorders or research programs funded by the National Institute of Neurological Disorders and Stroke, contact the Institute's Brain Resources and Information Network (BRAIN) at:

BRAIN
P.O. Box 5801
Bethesda, MD 20824
800-354-9424
www.ninds.nih.gov



More information about research on myasthenia gravis supported by NINDS and other NIH Institutes and Centers can be found using NIH RePORTER (projectreporter.nih.gov), a searchable database of current and past research projects supported by NIH and other federal agencies. RePORTER also includes links to publications and resources from these projects.



Information is also available from the following organizations:

Myasthenia Gravis Foundation of America, Inc.
355 Lexington Avenue, 15th Floor
New York, NY 10017
212-297-2156
800-541-5454
www.myasthenia.org

American Autoimmune Related Diseases Association
22100 Gratiot Avenue
Eastpointe, MI 48021
586-776-3900
www.aarda.org

Muscular Dystrophy Association
222 S. Riverside Plaza, Suite 1500
Chicago, IL 60606
800-572-1717
www.mda.org

U.S. National Library of Medicine
National Institutes of Health/DHHS
8600 Rockville Pike
Bethesda, MD 20894
301-594-5983
888-346-3656
www.nlm.nih.gov

NIH Publication No. 17-768

"Myasthenia Gravis Fact Sheet", NINDS, Publication date May 2017.

NIH Publication No. 17-768

Back to Myasthenia Gravis Information Page

See a list of all NINDS publications

Publicaciones en EspaƱol

Miastenia gravis

Prepared by:

Office of Communications and Public Liaison

National Institute of Neurological Disorders and Stroke

National Institutes of Health

Bethesda, MD 20892

NINDS health-related material is provided for information purposes only and does not necessarily represent endorsement by or an official position of the National Institute of Neurological Disorders and Stroke or any other Federal agency. Advice on the treatment or care of an individual patient should be obtained through consultation with a physician who has examined that patient or is familiar with that patient's medical history.

All NINDS-prepared information is in the public domain and may be freely copied. Credit to the NINDS or the NIH is appreciated.

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Date last modified: Fri, 2018-07-06 16:21"




Source:HERE





According to the CLEVELAND CLINIC,



"What is Myasthenia Gravis?

Myasthenia gravis (MG) is a neuromuscular disease, meaning that it affects the muscles and the nerves that control them. It is caused by a disorder in the immune system that causes the body to attack the area of the muscles where the nerves connect to them.

The immune system is the body’s natural defense against disease. Normally, when bacteria or other foreign substances enter the body, the immune system produces molecules called antibodies that attack the bacteria.

In people with myasthenia gravis, the immune system produces abnormal antibodies that prevent the muscles from receiving signals from the nerves that tell them when to relax or contract. This causes muscle weakness with symptoms that can include in double vision or blurred vision (eye muscle weakness), drooping eyelids (eyelid muscle weakness), difficulty with speaking and swallowing (throat muscle weakness) and weakness of the limbs.

When the immune system acts against healthy tissue by mistake, it is called an autoimmune disorder, with “auto” meaning “self. So myasthenia gravis is a neuromuscular autoimmune disease.

Myasthenia gravis is most common in young women and older men, but people of any age or either sex can get it.




Source:HERE





What Causes Myasthenia Gravis?

Scientists do not completely understand what triggers the autoimmune reaction in myasthenia gravis, but they do know that the thymus gland plays a role in the disease.

The thymus is a small gland that lies in the front part of the chest, beneath the breastbone, and extends into the lower part of the neck. It is most important early in life during immune system development.

A baby’s thymus gland weighs between .7 and 1.1 oz. The gland continues to grow and by puberty weighs 1.1 to 1.8 oz. The thymus gland’s job is thought to be completed by puberty, and after that it decreases in size. Over time, fat replaces portions of the gland. In older people the thymus weighs only .1 to .5 oz.

Tumors of the thymus gland are called thymomas (https://my.clevelandclinic.org/health/articles/6196-thymoma-and-thymic-carcinoma). Around 10-15 percent of people with myasthenia gravis have a thymoma Another 60%, however, will have other abnormalities of the gland including thymic hyperplasia (an enlarged gland).

The original association between the thymus gland and myasthenia gravis was made back in the early 1900’s when surgeons observed that removal of a thymoma resulted in the improvement in the patient’s myasthenia gravis. Ultimately surgeons began removing of the thymus gland in myasthenic patients without thymic tumors and a similar response was noted.

Research into the causes and treatments of myasthenia gravis will help scientists learn more about the role of the thymus in the disease.




Source:HERE






How is Myasthenia Gravis Treated?

The key to treatment of myasthenia gravis begins with an accurate diagnosis. The evaluation is usually directed by a Neurologist and can involve blood tests, nerve testing and tests involving administration of medicines in order to differentiate myasthenia gravis from other disease of muscles and nerves.

Once the diagnosis has been confirmed, a treatment plan is developed with the goal of reducing the number of antibodies causing the disease and/or improving the communication between the nerves and muscles. The ultimate results is improving muscle strength.


Medical treatment options include:

Medicines that suppress antibody production or improve nerve signal transmission
Plasmapheresis, a procedure that removes antibodies from the blood
High-dose intravenous immune globulin, the infusion of normal antibodies from donated blood to temporarily modify the immune system
Surgical treatment is thymectomy, removal of the thymus gland. This is the treatment for patients with thymomas, but is also considered for patients with MG who do not have thymomas.

At Cleveland Clinic, the Thoracic Surgeons are part of the treatment team evaluating patients and identifying the most appropriate combination of therapies for each individual.






Procedure Details


What are the results of thymectomy?

The goal of a thymectomy is to remove the source of abnormal antibody production causing the disease thus leading to resolution of symptoms. The benefits of thymectomy are not realized immediately after surgery, thus patients will continue with there medical regimen after the procedure with the goal of weaning those medications over time.Individual response to thymectomy varies depending on the patient’s age, response to prior medical therapy, the severity of the disease and how long the patient has had myasthenia gravis. In general, 70 percent of patients have complete remission or significant reduction in medication needs within a year of the procedure. The other 30 percent of patients who have thymectomy experience no change in their symptoms. According to the American Association of Neurologists, patients who have thymectomy are two times as likely to experience remission as those who have medical treatment alone.





How does a doctor determine which patients with myasthenia gravis should undergo thymectomy?

Thymectomy is recommended for all patients with thymomas and for patients under 60 who have mild to moderate muscle weakness due to myasthenia gravis. Thymectomy generally is not used for treating patients with myasthenia gravis that affects only their eyes.Thymectomy appears to be most effective when it is performed six to 12 months after the onset of symptoms. It is important to talk to your doctor early in your diagnosis about thymectomy as an option for treatment.




How is thymectomy performed?

Thymectomy can be performed by several different surgical techniques:

Transsternal thymectomy: In this procedure, the incision is made in the skin over the breastbone (sternum), and the breastbone is divided (sternotomy) to expose the thymus. This approach is commonly used for heart surgery. The surgeon removes the thymus through this incision as well as any residual fat in the center of the chest which may harbor extra thymic cells. This approach is commonly used when the patient has a thymoma.

Transcervical thymectomy: In this procedure the incision is made across the lower part of the neck, just above the breastbone(sternum). The surgeon removes the thymus through this incision without dividing the sternum. This is mostly used in patients without thymoma with certain body-types.

Robotic thymectomy and Video-assisted thorascopic thymectomy (VATS): These Minimally invasive techniques use several tiny incisions in the chest. A camera is inserted through one of the incisions and the surgery is performed with video guidance. The surgeon removes the thymus by using special surgical tools inserted into the other incisions. In a robotic-assisted procedure, the surgeon uses robotic arms to perform the surgery. The goal is to provide the same result as the more invasive transsternal approach with less post-operative discomfort and a quicker recovery.





What type of thymectomy is the best for me?

The transsternal thymectomy is the most commonly performed procedure, however there are no proven differences in outcomes with less invasive approaches. Your neurologist and surgeon will guide you in making a decision about the type of thymectomy you should have. Your surgeon will make a recommendation based on whether a thymoma is present and other factors related to your history and anatomy.There currently is no scientific evidence that proves one type of thymectomy is better than the other in terms of outcomes. To make the best decision for yourself, you should be informed about the different types of thymectomy and consult with your neurologist and surgeon. You also may want to seek a second opinion.






Risks / Benefits
What are the risks of thymectomy?




Complications are rare, but the risks include:

Infection
Bleeding
Injury lung
Nerve injury
Your doctor will evaluate your personal risk based on your age and other medical conditions.





Additional Details

How can I find a doctor who can evaluate me for thymectomy or provide a second opinion?
Thymectomy is performed by a thoracic surgeon, a surgeon who operates on the chest. This is a relatively rare procedure and should be performed by a surgeon with experience specifically in this procedure. In addition, the best outcomes are achieved by a multidisciplinary team of neurologists and thoracic surgeons with a cohesive treatment plan.

Doctors who perform this surgery (https://my.clevelandclinic.org/departments/heart/depts/thoracic-surgery#doctors-tab)
Thoracic Surgery Department (https://my.clevelandclinic.org/departments/heart/depts/thoracic-surgery)
For a referral to a physician, contact us (https://my.clevelandclinic.org/departments/heart/appointments-locations) or call the Miller Family Heart & Vascular Institute Resource & Information Nurse at 216.445.9288 or toll-free at 800.289.6911. We would be happy to assist you.





Resources

If you need more information, click here to contact us (https://my.clevelandclinic.org/departments/heart/appointments-locations), chat online with a nurse (https://my.clevelandclinic.org/departments/heart/appointments-locations#resource-nurse-tab) or call the Miller Family Heart and Vascular Institute Resource & Information Nurse at 216.445.9288 or toll-free at 866.289.6911. We would be happy to help you.





Condition Information

Myasthenia Gravis (https://my.clevelandclinic.org/health/diseases/17252-myasthenia-gravis-mg-)




Treatment Guides

All Miller Family Heart & Vascular Institute Treatment Guides (https://my.clevelandclinic.org/departments/heart/patient-education/treatment-guides)



This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or healthcare provider. Please consult your healthcare provider for advice about a specific medical condition. This document was last reviewed on: 04/14/2015"












Helpful Links & Resources for Myasthenia Gravis:

http://www.myasthenia.org/CommunitySupport/SupportGroupCalendar.aspx

https://www.elderneedslaw.com/blog/elder-law-and-myasthenia-gravis

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

https://medlineplus.gov/druginfo/meds/a682229.html

https://www.rxlist.com/mestinon-drug/patient-images-side-effects.htm#whatis

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