What Is Myasthenia Gravis?
Myasthenia Gravis is a chronic, neuromuscular autoimmune disease that affects the voluntary muscles of the body. Myasthenia Gravis causes differing degrees of weakness in the skeletal muscles of the body.
While once considered a grave disease, current treatments have ensured that most people who have Myasthenia Gravis go on to lead a normal life with a normal life expectancy.
The features of Myasthenia Gravis include muscle weakness that increases during activity and decreases after resting. The muscles that control things such as eye control, facial expression, chewing, talking and swallowing are generally (but not always) involved. The muscles that control limb movements as well as breathing may be affected as well.
What Causes Myasthenia Gravis?
This chronic condition, Myasthenia Gravis, is caused by a defect in the transmission of nerve impulses to the muscles. The normal communication between the nerve impulse and muscle is interrupted at the neuromuscular junction. The neuromuscular junction is the area where the nerve cells connect with the muscles they control.
Normal Pathophyisology Of Nerve Impulses:
In a normal person, the impulses travel through the nerve, and the nerve endings release acetylcholine (a neurotransmitter). This neurotransmitter then travels from the neuromuscluar junction where it binds to - and activates - the acetylcholine receptors which generate a muscle movement.
Pathophysiology Of Nerve Impulse Generation In Someone With Myasthenia Gravis:
For someone who has Myasthenia Gravis, their body's immune system creates antibodies that alter, block, or completely destroy the acetylcholine receptors at the neuromuscluar junction. This prevents contraction of the muscle.
The Thymus Gland And Myasthenia Gravis:
The thymus gland, an innocuous looking gland that lies beneath the breastbone, has an important part of developing the immune system in early life - the cells of the thymus are a part of the body's immune system.
The thymus gland is large in infants and grows slowly through puberty, when it shrinks and is replaced by fat cells.
Adults with Myasthenia Gravis have an abnormally large thymus gland that contains clusters of immune system cells that indicate lymphoid hyperplasia. Lymphoid hyperplasia is usually found only in the lymph nodes and spleen during an immune response.
Some people who have Myasthenia Gravis develop tumors of the thymus gland - called thymomas. These thymomas are generally benign, but can become cancerous.
Research indicates that there is some link between Myasthenia Gravis and the thymus gland, though precisely what that link is, no one is certain yet. Research is being conducted to ascertain what the link is between the gland and Myasthenia Gravis.
Who Has Myasthenia Gravis?
Myasthenia Gravis is an autoimmune condition that can span all ethnicity and genders. Most commonly, Myasthenia Gravis affects women under forty and men over sixty, but Myasthenia Gravis can occur at any age.
Myasthenia Gravis is not a genetic disease - meaning it's not inherited (although Myasthenia Gravis does run in certain families), nor is it something that is contagious.
What Are The Types Of Myasthenia Gravis?
There are several types of Myasthenia Gravis. These include (in alphabetical order):
Congenital Myasthenia Gravis (also known as Congenital Myasthenic Syndromes): this form of MG is not related to an autoimmune disease, but believed instead to be genetic. The three types of Congenital Myasthenia Gravis include: Pre-Synaptic Defects, Synaptic Defects and Post-Synaptic Defects.
The symptoms of this type of Myasthenia Gravis are similar to Immune-Response MG, but because of the differing underlying causes, treatments and prognosis are varied.
Immune-Response Myasthenia Gravis: this is the most common form of Myasthenia Gravis and is caused by autoimmune disease.
Juvenile Myasthenia Gravis: Juvenile Myasthenia Gravis is also caused by an autoimmune disease. The symptoms and treatment of Juvenile Myasthenia Gravis are similar to the adult version of Myasthenia Gravis. Prognosis of Juvenile Myasthenia Gravis is dependent upon whether or not the child developed MG before or after puberty began - prepuberty development of Myasthenia Gravis is associated with a greater possibility of remission.
Neonatal Myasthenia Gravis (also known as Neonatal Transient MG) is not an autoimmune disease, instead, it's caused by the prenatal transfer of MG antibodies. The symptoms tend to pass once the antibodies have been cleared from the bloodstream of the infant.
Ocular Myasthenia Gravis: this type of Myasthenia Gravis is an autoimmune attack upon the receptors of the nerve muscle synapse, that leads to weakness and fatigue of the eye muscles. While symptoms of Ocular Myasthenia Gravis often begin in the eye, general weakness and other related symptoms usually follow within three years.
What is the Classification System For Myasthenia Gravis?
Myasthenia Gravis has recently been divided into several classifications based upon severity of the disease and clinical features of Myasthenia Gravis.
Class I: Ocular weakness; perhaps with eye closure. All other muscle strength, however, is normal.
Class II: Mild weakness that affects muscles besides the ocular muscles. Ocular weakness may be present with any type of severity.
Class II: Moderate weakness affecting muscles other than the ocular muscles. Any degree of ocular weakness may be present.
Class IV: Severe weakness in muscles other than the ocular muscles. Any degree of ocular weakness may be present.
Class IV: Intubation - with or without mechanical ventilation - outside of routine post-operative management.
What Are The Symptoms of Myasthenia Gravis?
While Myasthenia Gravis can affect almost any voluntary muscles, the muscles most often affected are the following:
- The muscles that control the eyes and movements of the eyelids
- The muscles that allow for facial expression
- The muscles associated with swallowing
Generally, the first symptom that a person with Myasthenia Gravis has is weakness in the muscles around the eye, although others may notice slurred speech and challenges swallowing.
The amount of weakness varies greatly among those who have Myasthenia Gravis, and can be a localized form, such as the case with:
- Ocular Myasthenia - weakness limited to the eye muscles
Or a generalized form, in which a number of muscles are affected.
Symptoms may appear to be:
- Ptosis - drooping of the eyelid(s)
- Diploia - blurred or double vision
- Dysarthia - impaired speech
- Waddling gait
- Difficulty walking
- Shortness of breath
- Changes in facial expression
- Problems with swallowing
- Weakness in limbs, fingers and neck
How Is Myasthenia Gravis Diagnosed?
Weakness, one of the first noticeable symptoms of Myasthenia Gravis is a very non-specific symptom, which can be attributed to any number of disorders. As such, the diagnosis of Myasthenia Gravis may be delayed or missed for years. When diagnosing Myasthenia Gravis, the following techniques may be used:
Careful, Detailed Medical History - the doctor should review the person's medical history as well as provide a physical and neurological examination in which the doctor looks for changes in the eye movement or muscle weakness without changes in the way the person can feel things. Then, some of the following tests may be ordered.
Laboratory Blood Tests - blood tests can determine if the person has immune molecules or acethylcholine receptor antibodies in their circulating blood. Most patients with Myasthenia Gravis have elevated amounts of both of these antibodies.
Edrophonium Test - an IV of edrophonium chloride (which blocks the breakdown of acetylcholine and temporarily increases acetylcholine levels at the neuromuscular junction) will be administered to temporarily relieve the weakness associated with Myasthenia Gravis.
Nerve Conduction Study - allows for the study of specific muscular fatigue by repetitively stimulating the nerves. This test can determine any weakening of the muscle receptors after the nerves are stimulated by small electrical pulses.
Single Fiber Electromyography (also known as the jaunty EMG) may also be used to detect any impairment to the nerve-to-muscle transmission. EMG is used to measure the electrical potential of muscle cells after the stimulation of single muscle fibers by electrical pulses.
CT/MRI diagnostic imaging studies may be performed to identify if a person has a thymoma as well.
Pulmonary Function Tests - used to measure strength of breathing, can help determine the likelihood of respiratory failure during a myasthenic crisis.
What Is A Myasthenic Crisis?
A myasthenic crisis happens when the muscles that are associated with breathing weaken so much so that the ventilation is not enough to sustain their lives. This is a medical emergency in which a respirator or ventilator is used to help the person to breathe.
A Myasthenic Crisis may be brought on for a number of reasons:
- Adverse medication reactions.
A Myasthenic Crisis is a medical emergency.
How Is Myasthenia Gravis Treated?
Although this is a life-long disease, generally, Myasthenia Gravis is controllable.
Therapies To Control Myasthenia Gravis:
Physical therapy may be used to increase muscle strength.
Plasmapheresis, a procedure in which the blood serum with the abnormal antibodies associated with Myasthenia Gravis are removed.
High Doses of IVIG - this immunoglobulin can temporarily modify the immune system by infusions of antibodies from donated blood.
Medications To Control Myasthenia Gravis:
Anticholinesterase agents can improve neuromuscular transmission of nerve impulses as well as increase muscle strength.
Immunosupressive Drugs can be used to improve muscle strength while suppressing the creation of abnormal antibodies.
Surgical Interventions To Control Myasthenia Gravis:
Thymectomy - or a surgical removal of the thymus gland, can reduce symptoms for some people who have Myasthenia Gravis. A thymectomy is especially recommended for people who have thymomas.
What's The Prognosis For Someone With Myasthenia Gravis?
With proper care and treatment, most people who have Myasthenia Gravis can improve muscle weakness and lead relatively normal lives. Sometimes, Myasthenia Gravis goes into remission (temporarily or permanently), which means that medications and therapies can be discontinued.
The goal of a thymectomy is a stable and sustained remission and tends to occur in about 50% of people who have undergone a thymectomy.
Rarely, the weakness of Myasthenia Gravis can cause respiratory failure, requiring immediate medical intervention.
Tips For Living With Myasthenia Gravis:
Care for someone with a chronic condition doesn't end when the doctor's visit is over. Here are some tips for living with Myasthenia Gravis:
Read more about living with a chronic illness.
Change your eating routine - getting enough calories is very important for anyone with a chronic illness. Eat when your muscle strength is good and take your time while chewing. Rest between bites if you must. Try eating smaller, frequent meals. Avoid sticky foods and try to eat as many soft foods as possible.
When possible, use electronic devices and power tools to save your energy. An electric toothbrush can be very handy to reduce muscle usage.
If double vision is a problem, wear an eyepatch especially while reading or watching TV. Be sure to switch sides to avoid ocular strain.
Install home safety devices - hire someone to put in grab bars and railings in places you may want to have additional support (such as in the bathroom). Ensure that the floors in your house are clear from clutter to avoid falls.
Make a plan for everything you do - plan activities around the times in which your medications give you the highest level of energy. Eliminate any extra trips and ask for help going to the store and running errands.
Don't hesitate to ask others for help. There's no shame in needing some help around the house or with chores.
Additional Myasthenia Gravis Resources:
Myasthenia Gravis Foundation of America - is the only national volunteer health agency in the United States dedicated solely to the fight against myasthenia gravis.
Myasthenia Gravis Alliance: is an alliance of patients, families, health care professionals, and other concerned individuals from all ethnic backgrounds, countries, and voices of the world. We are dedicated to empowering people living with Myasthenia Gravis to maximize the quality of life by educating patients and health care professionals, support groups, and literature, while working together with the medical community towards a cure.
Myastinia Gravis Association Of BC provides peer support for people living with Myasthenia Gravis and their families. Membership and support can be particularly helpful to the newly diagnosed.