What is Myasthenia Gravis (MG)?
Myasthenia Gravis is a chronic autoimmune neuromuscular disease that causes weakness in skeletal muscles. The name translates from Latin and Greek origins to “grave, or serious, muscle weakness”. This disease targets muscles that are responsible for breathing and moving body parts, like arms and legs, and is worse after active periods but improves with rest. Often, muscles that control talking, chewing, swallowing, facial expressions, the eyes, breathing, limb movement, and the neck are affected.
Over half of MG cases, eye problems were the first sign. These include ptosis, which is the drooping of one or both eyelids, and diplopia, double vision that improves if one eye is shut. Throat and face muscle symptoms are the first sign in about 15% of those who develop myasthenia gravis. These are the most common symptoms seen in myasthenia gravis patients.
Other symptoms include weakness of the neck, arms, and legs. These don’t usually present themselves without the above symptoms. Legs are less often affected than arms but may cause patients to waddle. More seriously, breathing can be affected and can be a critical issue.
- Ptosis – Drooping of one or both eyelids
- Diplopia – blurred or double vision (horizontal or vertical)
- Changes facial expression
- Altered speaking
- Trouble chewing and/or swallowing
- Shortness of breath
- Dysarthria – impaired speech
- Difficulty holding up your head
- Weaknesses in muscles such as fingers, hands, arms, legs, neck
What causes Myasthenia Gravis?
Like with other autoimmune diseases, the body produces certain antibodies that block or destroy receptors from neurotransmitters. In the specific case of myasthenia gravis, these antibodies are blocking the neurotransmitter acetylcholine. The weakness in muscles results from the decreased nerve signals due to fewer receptor sites. Antibodies might also block the functioning of a protein like muscle-specific kinase from the neuromuscular junction which may lead to myasthenia gravis as well.
The thymus, a gland behind the breastbone, is strongly associated with MG as it controls immune function. In children, it grows gradually until puberty then decreases in size as it’s replaced by fat. While important in childhood for producing T-cells, adults with myasthenia gravis often have an enlarged thymus gland which may be the cause of an overactive immune system. Unfortunately, the function of the thymus gland is not fully understood yet.
As shown in this simplified video, a normal nerve (axon) terminal is able to send acetylcholine to the muscle motor end-plate but in myasthenia gravis cases the antibodies attach to the ACh receptors and block the acetylcholine from completing the signal.
Who gets Myasthenia Gravis?
Myasthenia Gravis is not distinguished from any gender, race, or ethnic group and any age range can be affected. However, women under 40 and men over 60 seem to be most commonly afflicted. This disease is not genetic nor contagious. An infant may, rarely, be temporarily affected by the mother’s antibodies, called neonatal myasthenia, but dissipates after a few weeks. A child of a healthy mother could have congenital myasthenia, another rare possibility, but it is different from myasthenia gravis and is not an autoimmune disorder.
Though many think the prevalence is higher, roughly 20 out of 100,000 people are diagnosed with MG in the US.
When to see a doctor?
If you are experiencing trouble with the above symptoms, consult your doctor.
How is it diagnosed?
Myasthenia gravis is diagnosed through a variety of tests. Doctors start with a physical and neurological exam to test reflexes, strength, senses, and coordination. From there further tests may be ordered including blood tests, CT or MRI scans, an electrodiagnostic test, and an edrophonium test, among other options.
How is it treated?
Unfortunately, there is no known cure for myasthenia gravis but the management of symptoms have improved over the years. Patients maintain a high quality of life and have a normal life expectancy.
Anticholinesterase drugs- improves neuromuscular transmission and improve muscle strength by slowing the breakdown of acetylcholine at the neuromuscular junction.
Thymectomy – some patients opt to remove their thymus gland to reduce symptoms and even cure some patients. A clinical trial funded by NINDS found that the surgery helped muscle weakness, and therefore, the patient’s’ need for immunosuppressive drugs.
Immunosuppressive medications – suppresses the production of abnormal antibodies to improve muscle strength. This must be closely watched by a trained physician as side effects can be significant.
IVIG – temporarily changes the way the immune system operates by injecting antibodies gathered from donors and they bind to the ones that cause MG and remove them from circulation.
Plasmapheresis – uses a machine to replace the bad antibodies in plasma with good plasma or a plasma substitute.
The Myasthenia Gravis Foundation of America (MGFA) is a great support organization that is dedicated to the fight against myasthenia gravis. They organize walks, raise awareness, and work with research groups. Check out their site for more information if you are a patient, loved one, caregiver, or just interested.
If you are in the Northern Virginia, DC, or Maryland area and are looking for more information or in need of care for myasthenia gravis, call us at 703-313-9111. Integrated Neurology Services provides extensive treatment options for patients with myasthenia gravis getting them the care they need and deserve.