Myasthenia gravis (MG) is a neuromuscular disorder that causes muscle weakness because nerve impulses are not adequately transmitted to muscles.
Like lupus or rheumatoid arthritis, myasthenia gravis is an autoimmune disorder, meaning the body’s own immune system attacks itself. In myasthenia gravis, the system attacks the connections between nerve and muscle.
The degree of muscle weakness varies tremendously and can range from a localized form limited to eye muscles to a generalized form in which many muscles are affected.
Myasthenia gravis may come on gradually or develop rapidly.
Myasthenia Gravis Symptoms
Myasthenia gravis causes weakness of the voluntary muscles – muscles that are under your control. Autonomic muscles of the heart and digestive track are usually not affected.
The muscles most often affected are those that control eye and eyelid movement, facial expression and swallowing.
Myasthenia gravis symptoms can include:
- Breathing difficulties
- Fatigue
- Problems chewing and swallowing (choking)
- Facial muscle weakness or paralysis such as eyelid drooping
- Difficulty talking
- Difficulty climbing stairs
- A drooping head
A common trait of this disease is muscle weakness that may increase during periods of activity and improve after periods of rest.
Myasthenia gravis is not a neuro-degenerative disease – typically patients do not get worse over time, as they might with other neurological diseases such as amyotrophic lateral sclerosis (ALS) or Alzheimer's disease.
Who does Myasthenia Gravis Affect?
Myathenia gravis can affect people of all ages, although it is most common in women younger than 40 and men older than 60. About 36,000 people in the United States have the condition.
Neonatal myasthenia gravis generally disappears after birth.
The muscle weakness can be seen in different ways depending on the severity of the disease, the cause of which remains unknown. If it is not diagnosed or treated, problems can become life-threatening – particularly if it affects the respiratory system.
Myasthenia Gravis Diagnosis
Diagnosing myasthenia gravis can be difficult because muscle weakness is common in many other disorders.
In addition to a medical history and physical and neurological examinations, your doctor may ask for other testing which may include:
- Blood test to detect elevated antibodies
- Edrophonium test to detect impact on muscles
- Nerve conduction study for specific muscle fatigue
- Electromyography (EMG) to test single muscle fibers
- Computed tomography (CT) or magnetic resonance imaging (MRI) to identify an abnormal thymus gland
- Pulmonary function testing to measure breathing strength
Myasthenia Gravis Treatment
Although there is no cure, with the appropriate care and treatment, good muscle function can be maintained in many patients.
Medications aimed at improving muscle weakness and strength are used to help control myasthenia gravis, as well as a number of procedures, all dependent on the patient's age, degree of symptoms and related medical problems.
Certain anticholinesterase agents improve neuromuscular transmission. Immunosuppressive drugs help suppress the production of abnormal antibodies.
Removal of the thymus gland can improve symptoms and, in some cases, cure patients. Other procedures can be helpful during periods of weakness. They include removing abnormal antibodies from the blood and providing the body with normal antibodies from donated blood.
A crisis or medical emergency in which the respiratory muscles are affected can be triggered by infection, fever, stress or adverse reaction to medication. This requires immediate attention and the patient may need a respirator.