- Myasthenia gravis is a medical condition where a person feels extreme fatigue and weakness of the voluntarily controlled muscles. The cause of this condition is disruption of normal communication between the nerves and muscles. This condition has no proper cure. Treatment comprises of symptom management. Myasthenia gravis more commonly affects women who are less than 40 years of age and men who are more than 60 years of age; however, this condition can affect anyone from any age. There is no cure for this disease. Treatment comprises of alleviating the symptoms and managing the symptoms using medications (corticosteroids, immunosuppressants), therapies (plasmapheresis, IVIg) and surgery (thymectomy).
Causes of Myasthenia Gravis
- Antibodies: When a person is affected by myasthenia gravis, the immune system starts to produce antibodies which interrupt or destroy the muscles’ various receptor sites for a specific neurotransmitter known as acetylcholine. Due to decrease in the receptor sites, our muscles are not able to get the required nerve signals and this causes fatigue and weakness in them. The antibodies produced by our immune system could also interrupt the function of a muscle-specific receptor protein, tyrosine kinase, which helps in formation of the nerve-muscular junction. Disruption in this protein’s function by the antibodies can also result in myasthenia gravis.
- Thymus Gland: According to research, any problem with the thymus gland, such as tumor, can also lead to the production of the antibodies and to myasthenia gravis.
Antibody-Negative Myasthenia Gravis: If there are other causes leading to myasthenia gravis, other than antibodies, then it is known as antibody-negative myasthenia gravis. The cause for this type could be genetic factors.
- Neonatal Myasthenia Gravis: Sometimes mothers suffering from myasthenia gravis can give birth to children with myasthenia gravis. This type is known as neonatal myasthenia gravis and it occurs very rarely. Prompt treatment helps the children in recovery from this condition.
- Congenital Myasthenic Syndrome is a rare condition where children are born with hereditary and a rare type of myasthenia gravis.
- Worsening Factors: Myasthenia gravis worsens due to factors, such as illness, fatigue, stress, excessive heat and certain medications such as beta blockers, quinine, quinidine sulfate, quinidine gluconate, phenytoin, certain antibiotics and anesthetics.
- The muscles affected by myasthenia gravis get weaker upon repeated use and they improve with rest. Symptoms of myasthenia gravis worsen over the time and are at their worse in a few years from the beginning of the disease. There are some muscle groups which are more commonly affected than others; however, any voluntarily controlled muscles can be affected. The important sign, which indicates myasthenia gravis, is improvement in the muscle weakness after rest.
- Eye Muscles: The first symptoms often develop in the eye muscles and the patient experiences the following symptoms:
Ptosis (drooping) of the eye lids, either unilateral or bilateral.
Diplopia (double vision) in the eyes. This can be vertical or horizontal and gets better upon closing one eye.
Facial and Throat Muscles:
- Change in speaking patterns, such as the voice may become nasal or very soft.
Patient has swallowing difficulties and may choke easily. Sometimes, upon drinking liquids cause them to come out of the nose.
- Patient also has difficulty while chewing, as the muscles used when chewing tire out between the meals, especially if the patient is chewing something hard.
Patient’s facial expressions become very limited such so that he/she may not be able to smile or frown.
- Weakness of the neck, arms and leg muscles causes difficulty in holding up the head and makes the patient waddle while walking.
To summarize, in myasthenia gravis, depending on the affected muscle, the patient has difficulty with vision, breathing, chewing, swallowing, walking, head holding and using hands, arms or legs.
- Neurological examination to check for reflexes, muscle tone and strength, touch and sight senses, balance and coordination.
- Edrophonium or Tensilon test.
- Ice pack test.
- Blood tests to check for presence of abnormal antibodies.
- Repetitive nerve stimulation.
- Single-fiber electromyography (EMG).
- CT scan.
- MRI scan.
- Pulmonary function tests to check respiratory function.
Treatment for Myasthenia Gravis
- Treatment of Myasthenia Gravis is aimed at alleviating the symptoms and trying to make the patient as much comfortable as possible and treatment comprises of:
Medications for Myasthenia Gravis
- Medications, such as cholinesterase inhibitors (pyridostigmine) help in improving the nerves and muscles communication and also help in enhancing the strength and contraction of the muscles. Side effects include nausea, stomach upset and excessive sweating and salivation.
- Corticosteroids (prednisone) help in slowing down the immune system and reducing the production of antibodies. Side effects include: Bone thinning (osteoporosis), diabetes, weight gain and increased chances of certain infections.
- Immunosuppressants, such as azathioprine, mycophenolate, and tacrolimus, are those medications which bring changes in our immune system. Side effects include: Gastrointestinal upset, nausea, vomiting, increased risk of infection, damage to the liver and kidney.
- Plasmapheresis is a procedure which has a filtering process resembling dialysis. The patient’s blood is passed through a machine which filters and removes the antibodies which are present in the blood and are blocking the transmission of signals from the nerve endings to the receptor sites of the muscles. Patient benefits from this therapy for a few weeks only and the treatment needs to be repeated again. Repetitive treatment makes access to the vein difficult and eventually a catheter needs to be implanted into the chest for continuation of this procedure.
- Risks of plasmapheresis include: Hypotension, muscle cramps or problems with heart rhythm. Some patients also have an allergic reaction to the solution which is used for plasma replacement.
- IVIg or Intravenous Immunoglobulin: In this therapy, normal antibodies are introduced into the patient’s body, which changes the response of the immune system. The benefits of IVIg are seen in a week and they last for about 4 to 6 weeks. The risks of this procedure are lesser than immune-suppressing therapy and plasmapheresis. Side effects are mild and include dizziness, chills, fluid retention and headaches.
Surgical Procedures for Myasthenia Gravis
- Around 16% of the patients suffering from myasthenia gravis also have a tumor (thymoma) in the thymus gland. In such cases, surgery (thymectomy) is done to remove the thymus gland.
- If there is no thymoma, then also, removal of the thymus gland can help in improving the symptoms of myasthenia gravis. However, it may take many years to feel the benefits of thymectomy and sometimes it may not help at all.
- Thymectomy can be done as a minimally invasive surgery or an open surgery. Open surgery comprises of splitting the sternum in order to open the chest and reach the thymus gland to remove it.
- Minimally invasive surgery consists of: Video-assisted thymectomy and Robot-assisted thymectomy.