Practice parameter: Thymectomy for autoimmune myasthenia gravis (an evidence-based review) [RETIRED]

Abstract

The Quality Standards Subcommittee of the American Academy of Neurology is charged with developing practice parameters for neurologists for diagnostic procedures, treatment modalities, and clinical disorders. The selection of topics for which practice parameters are used is based on prevalence, frequency of use, economic impact, membership involvement, controversy, urgency, external constraints, and resources required. This paper addresses the role of thymectomy in the treatment of nonthymomatous autoimmune MG.In 1939, Blalock et al. 1 reported the remission of generalized MG in a 21-year-old woman after removal of a cystic thymic tumor. Subsequently, Blalock et al.2,3 performed thymectomy on MG patients without thymoma, found hyperplasia in the thymus glands, and reported improvement in at least half of their patients. Since these reports, thymectomy, with or without the presence of thymoma, has gained widespread acceptance as a form of treatment for MG.Because a definitive study of the effectiveness of thymectomy has never been done, 4,5 the role of thymectomy in the management of MG remains uncertain. Nevertheless, physicians have to advise their patients regarding the benefits of thymectomy based on the existing literature. Our goal is to develop evidence-based recommendations for clinicians considering thymectomy for patients with nonthymomatous autoimmune MG by performing a systematic review and analysis of the literature. Process. Identification and selection of studies.We searched the National Library of Medicine's Medline database from 1966 to February 1998 using the medical subject headings "myasthenia gravis" (restricted to the surgery subheading) and "thymectomy." To identify articles published before 1966, or missed by our original search strategy, we reviewed the references of the identified articles.We classified the resulting articles into the following categories: Class II, controlled but nonrandomized studies describing outcomes in MG patients with and without thymectomy; and Class III, uncontrolled case series describing outcomes in patients with or without thymectomy.Within a given controlled (Class II) study, we planned to describe the therapeutic effect of thymectomy by comparing the rate MG patients receiving thymectomy achieved desirable outcomes with the rate MG patients not receiving thymectomy achieved desirable outcomes. The nonrandomized nature of Class II studies often introduces differences in the baseline characteristics of the thymectomy and nonthymectomy patient groups that can effect MG outcomes independent of thymectomy. To the extent possible, we planned to adjust for these confounding differences in baseline prognostic characteristics. In the absence of randomized controlled trials, such adjustments are critical for estimating the actual therapeutic effect, if any, of thymectomy. 6Between uncontrolled (Class III) studies, comparisons of outcome rates in thymectomy and nonthymectomy MG patients introduce additional confounding baseline differences.6 These additional confounde...

Immunosuppression of experimental autoimmune myasthenia gravis by mycophenolate mofetil

“…Thymectomy is nowadays a widely accepted and practiced form of treatment for MG and is performed in an attempt to induce complete remission or to reduce long-term need for immunosuppression (Gronseth and Barohn, 2000). In contrast, anti-cholinesterase agents are frequently used in the early disease course to decrease MG symptoms as they inhibit acetylcholine esterase from hydrolyzing acetylcholine.…”

Thymectomy in Myasthenia Gravis

“…Age, gender, and severity of the MG Response to thymectomy appears to be roughly comparable in mild, moderate, and severe MG [14]. Mao et al [15] evaluated prognostic factors of remission in MG after thymectomy by evaluating findings of 18 retrospective studies.…”

The Role of the Thymus in the Pathogenesis of Myasthenia Gravis

“…For patients with thymoma, thymectomy is necessary to prevent death by tumor invasion and/or metastasis. However, no evidence-based studies for MG treatment are available and a recent study, which summarized previous reports concerning the clinical outcome after thymectomy, showed no significant benefit of thymectomy in MG patients without thymoma (Gronseth and Barohn 2000). However, many reports have found that the clinical benefit of thymectomy is greatest in EOMG.…”