Nurses and nursing students find that they need to learn and stay up on autoimmune disorders. In this article we will outline Myasthenia gravis in the hopes of keeping the current information up to date for the nursing field.
Myasthenia gravis is an autoimmune disorder. Autoimmune in short means that the body is attacking itself. This disorder is characterized by fatigue and generalized weakness of any of the muscles that are under voluntary control. This disease attacks the peripheral nervous system (PNS), which is outside the brain and spinal cord. It can surface at any age, but is seen more in women over 40 and men over 60 years of age.
Myasthenia gravis causes a breakdown in normal transmission between nerves and muscles. While there is no cure for myasthenia gravis, there are treatments available to decrease the signs and symptoms.
Signs and symptoms:
Drooping eyes (ptosis), one or both
Double vision (diplopia)
Change in speaking
Difficulty with chewing or swallowing
Difficulty holding head up from causing weakness in neck
The thymus gland which is part of your immune system is believed that it may maintain or trigger the production of antibodies that block acetylcholine. While the thymus gland is small in adults, it is possible that some adults may have an abnormally large thymus or a tumor on the thymus (thymomas). Thymomas are not usually cancerous (malignant).
Antibody production is thought to be one of the main causes. Nerves communicate with muscles by releasing neurotransmitters or chemicals. These are like a lock and key as the neurotransmitters will fit exactly in the receptor sites of the muscles.
When there is a diagnosis of myasthenia gravis, the immune system will produce antibodies that will block and/or destroy many of the the receptor sites of the muscle for the neurotransmitter called acetylcholine. Since there are fewer receptors, the muscles will receive less nerve signals. This will result in weakness.
Antibodies may also block a function of a protein called tyrosine kinase. This is a nerve-muscular junction forming protein. When this protein is blocked, the patient go into myasthenia gravis.
It is important to note that any stress or illness may worsen myasthenia gravis.
Myasthenic crisis can be a life threatening issue that happens when the muscles that control breathing become weak and unable to support the respirations necessary for sustaining life. At this point the patient may need to be intubated and placed on a ventilator.
Edrophonium test aka Tensilon test. If positive then a diagnosis of myasthenia gravis can be made.
Cholinesterase inhibitors: Mestinon (pyridostigmine), improves communication between muscles and nerves. While this medication is not a cure, it may help with muscle strength and contraction.
Steroids: Corticosteroids such a prednisone, suppress antibody production by inhibiting the immune system.
Immunosuppressants: to alter the immune system.
IV immunoglobulin (IVIg): Alters the immune response by providing body with normal antibodies. This therapy may take up a week before results are seen, however, this carries much lower side effect then by having plasmapheresis. Improvement if any will last less than 1-2 months.
Plasmapheresis: This procedure is similar to dialysis. The blood will be sent through a machine that will remove antibodies that block the transmission signals from the nerve endings to the muscles receptor sites. It should be noted that the effects of having plasmapheresis last less than a month.
Always monitor for respiratory distress as patients can Myasthenic crisis and require an artificial airway.
Patients may have decreased signs of infection with steroids and IVig as this will immunosuppress the patient. Any low grade temperature should be reported immediately.
Use thickened liquids as the muscles are weaker and may have a harder time swallowing.