Myasthenia Gravis is a neuromuscular disorder primarily characterized by muscle weakness and muscle fatigue. Although the disorder usually becomes apparent during adulthood, symptom onset may occur at any age. The condition may be restricted to certain muscle groups, particularly those of the eyes (ocular myasthenia gravis), or may become more generalized (generalized myasthenia gravis), involving multiple muscle groups. Most individuals with myasthenia gravis develop weakness and drooping of the eyelids (ptosis) weakness of eye muscles, resulting in double vision (diplopia) and excessive muscle fatigue following activity.
What are the causes of Myasthenia Gravis?
Myasthenia Gravis is a neuromuscular disorder that is usually caused by an autoimmune problem. Autoimmune disorders occur when the immune system mistakenly attacks healthy tissue. In this condition, antibodies (proteins which normally attack foreign, harmful substances in the body) attack the neurotransmitter substance called acetylcholine, which is a crucial substance for nerve cell and muscle communication. This results in the muscle weakness that characterizes the condition. The exact cause of this autoimmune reaction is unclear to the doctors.
Who is at risk?
Myasthenia Gravis is not inherited, and it is not contagious. It is not clear why people develop the disorder, although some researchers believe it could be from a genetic problem. For women, the disorder usually starts in their 20s and 30s for men, usually after age 50.
The main symptom of Myasthenia Gravis is weakness in the voluntary skeletal muscles, which are the muscles under your control. This weakness occurs with activity and can get better with rest. The failure of the muscles to contract normally occurs because they cannot respond to the nerve impulse. This is considered to be a blocked communication between nerve and muscle, and without the proper transmission of the impulse, weakness results.
Weakness associated with MyastheniaGravis typically gets worse with more activity and improves with rest. Symptoms may include:
- Trouble talking
- Problems walking up stairs or lifting objects
- Facial paralysis
- Difficulty breathing because of muscle weakness
- Difficulty swallowing or chewing
- Hoarse voice
- Drooping of eyelid
- Double vision
Not everyone will have every symptom, and the degree of muscle weakness can change from day to day. The disease typically progresses over time if left untreated.
How Myasthenia Gravis is diagnosed?
Your doctor will perform a complete physical exam
, as well as take a detailed history of symptoms. He or she will also do a neurological exam. This may consist of:
- Checking your reflexes
- Looking for muscle weakness
- Checking for muscle tone
- Making certain your eyes move properly
- Testing sensation in different areas of your body
- Seeing if you can perform certain movements, like touching your finger to your nose
Other tests that can help your doctor diagnose the condition include:
- Repetitive nerve stimulation test
- Blood testing for antibodies associated with Myasthenia Gravis
- Edrophonium (Tensilon) test: a drug called Tensilon (or a placebo) is injected, and the patient is asked to perform muscle movements under doctor observation
- Imaging of the chest, using CT scans or MRI, to rule out a tumour
Common treatments for myasthenia gravis include:
- Medications such as Mestinon (pyridostigmine bromide) and Prostigmin (neostigmine bromide)
- Corticosteroid medications such as prednisone
- Medications that suppress the immune system, such as Imuran (azathioprine) and cyclosporine
- Removal of the thymus gland (thymectomy), the main gland in the immune system
- Plasma exchange (plasmapheresis), in which the person's blood plasma containing the abnormal antibodies is removed and fresh plasma is put back
People with myasthenia gravis can in most cases lead full lives. Sometimes the muscle weakness resolves to the point of not being a problem (called spontaneous remission). For some people, the weakness is only in the eyelids. For others, the weakness progresses to a point and stays at that level. Rarely, and usually in the first two years of the disorder, the weakness might extend to the muscles that control breathing, and the person will have to be hospitalized. There is no cure for myasthenia gravis, but the treatments are usually effective in minimizing its problems.