Surgical Thymectomy

Most neurologists advocate thymectomy for the majority of patients with generalized myasthenia without thymoma. Factors influencing the decision may include age, duration and severity of the disease, and response to medication. Although no adverse effects have been reported as a consequence of thymectomy in children, it is preferable to delay thymectomy until puberty if possible because of the established role of the thymus in development of the immune system. Also, although thymectomy has been advocated for elderly myasthenia gravis patients, there is uncertainty about the persistence of thymic tissue in such patients after the age of 60.

The goal of thymectomy as a treatment for myasthenia gravis is to induce remission, or at least improvement, permitting a reduction in immunosuppressive medication. The mechanism by which thymectomy produces benefits in myasthenia gravis is still uncertain. In general, acetylcholine receptor-antibody levels fall after thymectomy, although there are conflicting reports. On theoretical grounds, there are several possible mechanisms. First, removal of the thymus may eliminate a source of continued antigenic stimulation. If the thymic myoid cells are the source of autoantigen then their removal might allow the immune response to subside. Second, thymectomy may remove a reservoir of B cells that are secreting acetylcholine-receptor antibody. Third, thymectomy may is some way correct a disturbance of immune regulation in myasthenia gravis.

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