The thymus gland serves a vital role in T-cell production and regulation in the body and in mature immunity. The thymus gland's function is to receive "immature” T -cells that are created within the red bone marrow and teach the immature cells how to become functional, mature T- cells who are used solely to attack foreign cells. The thymus gland plays it's greatest role in childhood, enlarging until puberty where it subsequently begins to shrink at the onset of puberty and into full adulthood. As the thymus shrinks, its tissues are replaced by adipose tissue. According to researchers, the shrinking is due to the reduced role of the thyroid in adulthood – the immune system produces most of its T cells during childhood and requires very few new T cells after puberty. In a healthy adult, the thymus should be residual and continue to shrink throughout maturity.
While not fully understood, research shows a correlation between thymectomy as a surgical treatment for AChR and seronegative patients and an increase in long term stability and remission compared to patients who do not have surgical intervention. Experts do not all agree that thymectomy is an appropriate course of action for patients who present without thymoma (a tumor on the thymus gland that is typically benign but can be malignant in some cases and is seen in an estimated 20% of Myasthenics), however, a new study affirms the belief that thymectomy for non-thymoma patients is beneficial (some criteria excludes certain patient populations).
- Age, Onset, Severity and Type of MG (AChR, MuSK or Seronegative etc) all play a large role in the viability and efficacy of the thymectomy. Those studied and recorded who stand the best chance of achieving possible remission and stabilization are those who have it removed within the first year of diagnosis, are AChR positive and are generally under the age of sixty, although those under fifty are preferred unless a tumor (thymoma) is present. Hyperplasia of the thymus gland is considered by some to be a main aggressor in more moderate and severe cases. Removal of a hyperplastic gland has been documented to show an increase in the stability of symptoms and offers the greatest increase for remission. MuSK and thymoma myasthenics have the potential to worsen with the thymectomy. It is encouraged that your specialist helps you navigate if you are eligible for this procedure.
- Thymoma is a usually benign tumor that is created from the surrounding epithelial cells of the thymus gland. A thymoma is found in roughly 10-15% of myasthenic patients and requires removal upon stabilization of the patient. In the rare event that the thymoma is malignant, surgical methods may not be enough and a doctor may want to involve an oncologist to employ chemotherapy or radiation to help ensure the thymoma is no longer a threat. It is estimated that up to one half of myasthenics with a thymoma will experience no symptoms of the tumor. Symptoms can include chest pain or pressure, difficulty swallowing and generalized myasthenic weakness. Thymoma is often discovered on chest x-rays, CT scans or MRI's.
- Scans such as x-rays, CT's and MRI's are used to help determine if a thymoma is present but they are often used as the sole diagnostic criteria for eligibility for thymectomy. However, because the thymus gland is anterior and superior to the heart and posterior to the sternum, it is very difficult to clearly discern the true nature of the thymus gland, if it is hyperplasiac or not and if removal is necessary. The thymus can also grow into the neck and throughout the chest cavity with finger like extensions and can be difficult to see all potential thymic tissue that has strayed from the gland in these scans.
- These scans should be a starting point and not a sole determinant.
- The different types of surgical approaches matter: Trans-sternal and VATs procedures are preferred methods to DaVinci (robotic), for better visualization, thymoma removal and long term stability in spite of the robotic approach being able to successfully remove the gland.
- Thymic tissue likes to hide away in adipose cells into the neck and throughout the chest cavity making it imperative that surgeons not only remove the located gland, but are able to clearly visualize the neck and entire chest cavity in order to ensure full removal of hidden, lingering tissue. Remaining thymic tissue can grow back and relapse a patient, sometimes worse than before they had surgery.
- While there are many approaches that surgeons have used and are comfortable with, there is more dynamic research backing the use of certain approaches than others in the full removal of residual tissue and in the long term in regards to stability and potential remission. Keep in mind that your surgeon will recommend what he or she is comfortable with and that may or may not be in your best interest. Individual health history, disease severity and other considerations must also be accounted for.
- Don't be afraid to shop around for a knowledgeable surgeon.