Myasthenia Gravis is an autoimmune disease in which the body’s defense system attacks nerve receptors, causing muscle weakness and inefficiency.
- Myasthenia Gravis is a chronic autoimmune condition
- Treatment involves surgical removal of the thymus, which can be done in a number of ways
- Non-surgical options such as plasmapheresis, immunoglobulin, and medications can help treat symptoms of myasthenia gravis but cannot cure the condition.
Myasthenia gravis is an autoimmune disorder in which the body attacks specific neurotransmitter receptors that bridge nerve endings and muscle tissues. This reduces the ability of acetylcholine, a neurotransmitter, to stimulate the muscles.
Those with myasthenia gravis experience increasing muscle weakness during activity, which is relieved during rest. The condition has a pronounced effect on muscles related to eye movement, talking, chewing, and swallowing. Other affected muscle groups include those involving breathing, which means that those with the condition may be vulnerable to respiratory paralysis. The exact cause is not fully understood, but the thymus gland, located under the breast bone, plays an important role in the immune system's attack on the acetylcholine receptors.
About 20 people out of 100,000 in the United States have myasthenia gravis, although it may be under diagnosed. Myasthenia gravis can affect any age, all races, all genders, and does not seem to be genetic. Spontaneous improvement and even remission sometimes happens without specific treatment.
There is no known cure for myasthenia gravis. However, several non-surgical treatment options may result in reduction or remission of symptoms.
Some medicines help improve nerve-to-muscle communication and strengthen muscles; other drugs prevent the body from producing abnormal antibodies.
Anticholinesterase agents such as neostigmine or pyridostigmine allow acetylcholine to remain at the neuromuscular junction longer than usual so that more receptor sites can be activated, which helps improve neuromuscular transmission and increase muscle strength. Corticosteroids and immunosuppressant agents may be used to suppress the abnormal immune system response that occurs in myasthenia gravis.
A physician must carefully monitor these medications because they may cause major side effects.
Plasmapheresis is a procedure that removes the clear part of the blood (plasma) containing abnormal antibodies and replaces it with donated, antibody-free plasma. Plasmapheresis may help improve muscle strength for 4 to 6 weeks. Plasmapheresis may require repeated exchanges because production of abnormal antibodies continues. It is often used during severe episodes of weakness or prior to surgery.
A blood product that helps to decrease the immune system's attack on the nervous system, immunoglobulin is delivered intravenously directly into the blood stream in high doses to counter the effect of abnormal antibodies. Intravenous immunoglobulin may be as effective as plasmapheresis.
Between 10-15% of those with myasthenia gravis have a tumor in the thymus gland, called a thymoma. (The thymus gland is located behind the breastbone and is an important part of the immune system.) Due to the risk of malignancy, thymoma removal is always recommended. But even in those without a tumor, surgical removal of the thymus gland, or thymectomy, greatly improves the condition in 70% of cases and in some cases the myasthenia gravis goes into remission.
Minimally Invasive Thymectomy
Thymectomy has traditionally been performed as an open procedure in which the central breast bone, or sternum is cut, and the chest opened (sternotomy). A sternotomy is major surgery, requiring three to five days in the hospital, and up to six weeks to recover.
But today, minimally invasive thymectomies allow surgeons to remove the thymus gland through a very small incision in the bottom of the neck just above the sternum, using a videoscope and tiny instruments. In video-assisted thoracoscopy (VATS), surgeons insert rigid-handled instruments through the incision, and see the surgery on a two-dimensional monitor. No bone is divided and only the skin is cut, and the surgeon can see the thymus gland directly from the neck without opening the chest. Benefits include less postoperative pain, shorter hospital stays, faster recovery from surgery, and a quicker return to full activity.
Bilateral VATS Thymectomy
The procedure may also be performed minimally invasively through the side of the chest, via video-assisted thoracoscopy (VATS). The surgeon creates two or three small (¾-inch) incisions. Small surgical instruments and a camera for viewing the procedure are inserted through the incisions. Surgery takes place entirely inside the closed chest. Benefits include reduced recovery time and less postoperative pain than the open approach. This is the most cosmetically appealing of thymectomy procedures due to the location and the small size of the incision.
In a robotic thymectomy the surgeon makes three tiny incisions — each about a half-inch long — on one side of the chest. The same tiny camera and surgical instruments used in a minimally invasive thymectomy are inserted through the incisions. But then the arms of the daVinci robot are attached to those instruments. The surgeon sits at a console, controlling the robotic arms, which separates the thymus gland from its surrounding tissue and bone and removes it through one of the incisions.
The advantages of robotic surgery over VATS alone is far greater control, which reduces the risk of complications even more. The extremely flexible instruments used in robotic surgery more closely replicates human wrist movement but without any shakiness. Surgeons can operate more easily and intuitively, and with much greater precision. They also view the surgical area up close through a magnified system that shows everything, such as pulmonary arteries, in three dimensions.
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