Myasthenia gravis and thymectomy: many doubts and few certainties.

Abstract

Myasthenia gravis (MG) is a rare autoimmune disease affecting neuromuscular transmission. The thymus plays a central role in the complex pathogenesis and perpetuation of this disease, being implicated in mechanisms of self-tolerance and autoimmunity. Since the study of Blalock [1] in 1944, who published the results of transternal thymectomy in a series of 20 patients affected by MG, thymectomy has become an essential part of the integrated treatment of this disease, yielding positive results in terms of improvement and remission of symptoms. The report by Keijzers et al .[ 2] in this issue of EJCTS provides the neurological and surgical results of robotic thymectomy in a large cohort of patients affected by MG. This study summarizes the main concerns regarding the role of thymectomy in MG patients. Despite a general agreement on the beneficial role of thymectomy for MG patients, to date no prospective randomized trials have addressed the question whether thymectomy is superior to medical treatment. This question is the subject of an ongoing international multicentre randomized clinical trial comparing thymectomy and prednisone therapy with prednisone alone [3]. The best available data come from a meta-analysis of 28 controlled but nonrandomized studies that showed MG patients undergoing thymectomy were twice more likely to attain medication-free remission than unoperated patients, 1.6 times more likely to become asymptomatic and 1.7 times more likely to improve [4]. In addition to this low level of evidence supporting thymectomy, several controversies still exist regarding the selection of candidates for surgery, the extent of thymic resection and the best surgical approach to be used [5]. Thus, a consensus on the best clinical practice has never been reached. For these reasons, when considering thymectomy for MG patients, clinicians have to think imperatively over the ratio between expected benefits and risks guaranteeing the best balance between the extent of resection, morbidity, patient acceptance and results. In our view, three key points are of paramount importance: (i) Surgical risk-benefit balance: A variety of surgical approaches have been described for thymectomy ranging from open (basic transsternal or the more aggressive extended transcervical and transsternal maximal thymectomy), to minimally invasive approaches (transcervical or video-assisted thoracoscopic thymectomy). When compared, each approach has its benefits and drawbacks. At this time, only non-randomized retrospective case series are available for comparison of various operative approaches. The heterogeneity of patient selection, the different timing and type of surgery, the several clinical classifications used, the different methods applied for the evaluation of results and many other confounding factors have made the analysis complicated, if not impossible (Class III evidence) [6]. Ideally, the less invasive surgical technique is desirable, assum