What is the role of the thymus and a thymectomy in Myasthenia Gravis?
- What is the thymus and what is a thymectomy?
- What is a thymoma?
- When should a thymectomy be done?
- How does a thymectomy fit in with the treatment of Myasthenia Gravis?
- What are some risks of a thymectomy?
- What should be expected after a thymectomy?
- What is the percentage of people who go into remission who have not had a thymectomy?
- Who is considered an experienced surgeon?
- What are the different methods of a thymectomy?
- What are the age limits for a thymectomy?
- What are the chances of developing an autoimmune disease from removal of the thymus gland?
The thymus is a gland located in the chest area that helps the immune system develop. A thymectomy is the removal of the thymus gland. The thymus may be removed as a treatment of Myasthenia Gravis in the hope of increasing the chance of remission (absence of symptoms and no need of medication) from the disease. It is thought that in some patients removal of the thymus reduces the production of antibodies against the nerve-muscle junction, which are producing the disease.
A thymoma is a tumor of the thymus gland. The tumor can grow and squeeze blood vessels, the heart and lungs and require removal. A thymoma may also metastasize to other organs. Fortunately, most patients can have the tumor removed and do well. Removal of the thymoma does NOT cure MG.
Most experts and some studies suggest that a thymectomy be done early in treatment. Most experts also recommend thymectomy for patients younger than 60 and who are otherwise healthy. Most experts do not recommend thymectomy for purely Ocular Myasthenia Gravis, but there are differences in opinion. Patients with immune MG tend to respond similarly to thymectomy whether they have antibodies to the acetylcholine receptors or not, but there is disagreement, with some experts thinking that patients without antibodies against the receptor do not benefit from thymectomy.
A thymectomy is NOT a cure, but may increase one’s chance for remission and may make the disease less severe. Thymectomy is only one component of the treatment for MG. Treating coexisting medical conditions, selecting appropriate specific therapy for MG (medications like Mestinon, prednisone, Imuran, cyclosporine, Cellcept, IVIg) limiting side effects of MG medications, caring for the psychological concerns of a chronic disease, and budgeting your energy level are all important. With all these components in place, the majority of patients improve significantly over the initial years of treatment. Most of my patients are able to carry on normal work (or schooling) and most hobbies. The majority are, however, still taking medicines to achieve this good result.
Thymectomy is a major surgery and there are risks of bleeding, collapsed lung, and post-operative infections. Pain in the region of the incision and the back should be expected from surgery. Because of anesthesia and the stress of surgery, patients with MG may become temporarily weaker after surgery. In addition, a patient with other medical problems may have more complications. Your surgeon, anesthesia team and neurologist should discuss these issues with you prior to surgery.
Most surgeons recommend decreased activity (no lifting items over 25 lbs. –including small children) and not to drive (a car accident with a healing sternum could be very dangerous) for 6-8 weeks. Most patients feel chest discomfort for about that same period of time. This gradually decreases, as does the need for pain medicine. It is important to remember that there may also be an increased weakness from the Myasthenia Gravis that is a separate symptom from the surgery recovery.
The studies for thymectomy treatment for Myasthenia Gravis are confusing because of different definitions of what “remission” is. For example, some physicians describe patients as being in remission if they are without symptoms, but are still taking medications. Also, many studies on remission were done before the modern medications were in use, or only followed patients for two years. With that said, some studies indicate remission rates of 80% and others 20%. There appears to be at most a 10% spontaneous remission rate (no treatment given but patients go into remission).
Thymectomies are not common procedures and a surgeon would be considered experienced if he or she performs 3-4 thymectomies per year. These cardiothoracic surgeons are performing other operations on the heart and lungs several times per week.
There have been many types of surgical procedures used to remove the thymus gland. Generally they fall into two categories: transcervical or transsternal. The transsternal approach involves going through the breastbone to remove the thymus gland. The transcervical approach involves a smaller incision above the breastbone across the neck. In my opinion (and many others), the transsternal approach removes more of the thymus gland and therefore is best. The transsternal approach does produce a larger scar. Recently a video-assisted technique, which uses smaller incisions, has been developed. However, there is not enough information at this time to determine its effectiveness. The most important aspect is to have an experienced surgeon to perform the procedure.
Thymectomies are an accepted form of treatment for Myasthenia Gravis. It is usually restricted to individuals, in otherwise good health, younger than 60 (although some experts would not restrict the age).
The recommendation to have a thymectomy is given to patients with thymus gland tumors and to young adults. For older patients, the recommendation depends on the severity of symptoms, life style, response to medications and side effects of these medications, all put together. The benefits and risks of MG must also be weighed against the risks of available treatment (both medical and surgical).
Removing the thymus gland does NOT increase your chance of developing autoimmune diseases.
For more information:
Go to the Myasthenia Gravis health topic.