Myasthenia Gravis: Causes, Symptoms and Treatment
Myasthenia gravis is a rare neuromuscular disease that causes muscles weakness by interrupting the connection between nerves and muscles. These muscles are mainly responsible for the movement of arms, eyes, and, legs, facial expression, talking, chewing, and breathing. The weakness of muscles increases during physical activities and generally improves after taking proper rest. It can occur at any age, but in women, it usually starts before the age of 40 years and in men, after the age of 60 years.
Following are the symptoms that persist with myasthenia gravis, which include:
- Blurred or double vision
- Sagging of eyelid
- Difficulty in swallowing or chewing
- Shortness of breath
- Impaired speech
- Weakness of eye muscles
- Difficulty in making facial expressions
- Weakness or fatigue in the body parts (arms, hands, legs, fingers, and neck)
The main causes of myasthenia gravis include:
- Antibodies: Myasthenia gravis is an autoimmune disease in which the immune system produces antibodies that attacks the neuromuscular junction and blocks the signal of nerves to the muscles, and therefore, muscles become tired and weak.
- Thymus gland: The thymus gland is a part of the immune system that controls the immune functions. In adults with myasthenia gravis, thymus gland becomes large and sometimes leads to a tumor.
- Other cause: In addition to the above causes, hereditary is also a rare cause of myasthenia gravis.
As myasthenia gravis progress, it leads to a serious complication, i.e., myasthenic crisis. It occurs when extreme weakness affects respiratory muscles that control breathing. The patient becomes unable to breathe which requires immediate medical emergency. The condition may be triggered by infection, surgery, stress, or adverse reaction to medicines.
The various methods to diagnose myasthenia gravis include:
- Neurological examination: The healthcare professional will check muscle tone and strength, coordination, sense of touch, and reflexes.
- Edrophonium test: In this test, the injection of edrophonium chloride is used and the signs of temporary relieve of muscle strength confirms a diagnosis of myasthenia gravis.
- Blood test: This is used to check the presence of abnormal level of antibodies which block the nerve signals to muscles.
- Imaging test: CT scan or MRI is used to check the presence of tumor in thymus glands.
- Single- fibre electromyography: This is used to check the electrical activity between the brain and the muscles.
- Ice pack test (placing an ice over the eyelid): This test is used to assess the improvement sings in patients with droopy eyelid but has limitations due to false-positive results.
Since, the cure of myasthenia gravis is not available, but to avoid some factors may help to prevent the worsening of this disease include:
- Mental stress
- Exposure to extreme temperatures
There are several methods which help to treat myasthenia gravis by improving muscle weakness include:
- Medications: Cholinesterase inhibitors such as pyridostigmine and neostigmine are used to enhance the signals between nerves and muscles. Corticosteroids (Prednisone) inhibit the immune system by inhibiting the natural production of adrenal hormones. Immunosuppressants like azathioprine, cyclosporine and methotrexate are also used to alter immune system.
- Intravenous immunoglobulin: Intravenous immunoglobulin injection works by binding to the antibodies that cause myasthenia gravis. Rituximab is the most recently approved as monoclonal antibody for this disease. It suppresses the immune system by reducing B-lymphocytes.
- Plasmapheresis: This is a filtering process that removes the harmful antibodies that disrupt the signals of nerve to muscle. It is used to give temporary relieve from muscle weakness.
- Surgery – Video-assisted thymectomy and robot-assisted thymectomy are used to remove the abnormal thymus gland.