Influence of ectopic thymic tissue on clinical outcome following extended thymectomy in generalized seropositive nonthymomatous myasthenia gravis

Enigmatic thymus: Variations in anatomical localisation of thymic tissue as an easily misdiagnosed congenital anomaly in surgical practice

We point out the issue of differential diagnosis regarding the finding of ectopically localised thymic tissue (a thymic cyst) in the neck. Thymic tissue can be found anywhere along its developmental tract of descent, from the angle of the mandible to the upper mediastinum. Disruption of the thymic descent can result in ectopically/abnormally localised islets of accessory thymic tissue, which may undergo cystic changes, as described in a case report by Sun et al. This anatomical variation of the thymus may be clinically misinterpreted as a neoplasm or other congenital anomalies as a branchial cyst, lymphatic malformation or cystic hygroma. The present editorial focuses on the challenge of establishing a diagnosis of ectopically localised tissue of thymus often presented as a lateral cervical mass, especially in the case of cystic variation/degeneration of this thymic tissue. We summarise hypotheses on the origin of such congenital cervical thymic cysts from the point of view of evolutionary history and embryology. We also discuss lesser-known facts about the anatomy, histopathology and developmental biology of the thymus as one of the most enigmatic organs in the human body.

Expression of Programmed Cell Death 1 Ligand 2 in Patients With Thymoma and Thymomatous Myasthenia Gravis

OBJECTIVES

This study aimed to examine the expression of programmed cell death 1 ligand 2 (PD-L2) in thymoma and thymomatous myasthenia gravis (MG).

METHODS

The records of 70 patients with thymoma receiving surgical resection between January 2017 and December 2018 were retrospectively reviewed. Thymoma PD-L2 expression was evaluated by immunohistochemistry staining. Associations between PD-L2 expression and clinicopathologic features were examined.

RESULTS

PD-L2 expression was positive in 41 patients (58.6%) and negative in 29 patients (41.4%). Of them, 33 had thymomatous MG. Patients with MG were more likely to be 50 years of age or younger (69.70% vs 35.14%); have more World Health Organization (WHO) type B thymomas (84.85% vs 64.86%); have tumors of smaller size (4.09 ± 2.33 cm vs 6.47 ± 2.42 cm); have positive PD-L2 expression (78.79% vs 40.54%); and have a higher percentage of PD-L2-positive cells, higher PD-L2 expression intensity, and score (all P < .05). Positive PD-L2 expression was associated with more type B thymomas, higher Masaoka-Koga stage, smaller tumor size, ectopic thymus, and MG (all P < .05). Factors significantly associated with MG were age under 50 years, tumor size less than 5 cm, and positive PD-L2 expression (all P < .05).

CONCLUSIONS

Thymoma PD-L2 expression is significantly associated with thymomatous MG and WHO histologic types B2 and B3.

Poor responses and adverse outcomes of myasthenia gravis after thymectomy: Predicting factors and immunological implications

Myasthenia gravis (MG) has been recognized as a series of heterogeneous but treatable autoimmune conditions. As one of the indispensable therapies, thymectomy can achieve favorable prognosis especially in early-onset generalized MG patients with seropositive acetylcholine receptor antibody. However, poor outcomes, including worsening or relapse of MG, postoperative myasthenic crisis and even post-thymectomy MG, are also observed in certain scenarios. The responses to thymectomy may be associated with the general characteristics of patients, disease conditions of MG, autoantibody profiles, native or ectopic thymic pathologies, surgical-related factors, pharmacotherapy and other adjuvant modalities, and the presence of comorbidities and complications. However, in addition to these variations among individuals, pathological remnants and the abnormal immunological milieu and responses potentially represent major mechanisms that underlie the detrimental neurological outcomes after thymectomy. We underscore these plausible risk factors and discuss the immunological implications therein, which may be conducive to better managing the indications for thymectomy, to avoiding modifiable risk factors of poor responses and adverse outcomes, and to developing post-thymectomy preventive and therapeutic strategies for MG.

Efficiency of ectopic thymectomy by three surgical approaches in non-thymomatous myasthenia gravis

Background

To explore the efficiency of ectopic thymectomy by the three surgical approaches of trans-sternum, right unilateral thoracoscopy and thoracoscopic subxiphoid in patients with non-thymomatous myasthenia gravis.

Methods

155 consecutive non-thymomatous myasthenia gravis patients who underwent extended thymectomy by 3 approaches including trans-sternum, right unilateral thoracoscopy and thoracoscopic subxiphoid in 1st affiliated hospital of Sun Yat-Sen University from January 2017 to October 2019 were reviewed. Differences of perioperative clinical characteristics in three surgical approaches were analyzed.

Results

Time to onset of myasthenia gravis (early or late) (p = 0.018), blood loss (p < 0.001), duration of operation (p = 0.031), duration and volume of thoracic drainage (p = 0.039 and p = 0.026), length of hospitalization (p = 0.039), the efficiency of ectopic thymectomy (p = 0.037), and the detection rate of ectopic thymus in the second quadrant (p = 0.018) were different among the three surgical approaches. In univariate logistic regression analysis, higher efficiency of ectopic thymectomy were associated with transsternal (OR 2.36, 95% CI 1.32–4.22, p = 0.011) and thoracoscopic subxiphoid approaches (OR 2.07, 95% CI 1.12–3.82, p = 0.033). In the multiple logistic regression analysis, the transsternal approach (OR 2.02, 95% CI 1.10–3.71, p = 0.024) was an independent protective factor for the efficiency of ectopic thymectomy.

Conclusions

Both the right unilateral thoracoscopic and thoracoscopic subxiphoid approaches have advantages over the transsternal approach in short-term postoperative recovery. Transsternal approach is still the best choice for ectopic thymectomy while thoracoscopic subxiphoid approach show the potential as an alternative way.

Myasthenia Gravis and Thymectomy

Myasthenia gravis (MG) is a rare autoimmune neuromuscular disorder. Though MG was diagnosed four centuries ago, its rational management started in 1930s. In the present era, MG is managed by multimodality care including pharmacological agents, plasmapheresis, intravenous immunoglobulins, and surgical thymectomy. Thymectomy has evolved from open trans-sternal to video-assisted thoracoscopic and robotic thymectomy. In this article, the concise history of MG, its clinical features, diagnosis, and management are described.

Robotic thymectomy for myasthenia gravis surgical techniques and outcomes

Myasthenia gravis (MG) is an autoimmune disorder in which antibodies are produced against post-synaptic acetylcholine receptors, thereby causing impairment of neuromuscular transmission. Diagnosis of MG is confirmed with the AChR antibody test and via an Electromyography. Although medical treatment with acetylcholinesterase inhibitors remains the main treatment of MG, in recent years thymectomy has become an integral part of the treatment algorithm. Numerous factors such as the Patient’s age, presence of AChR antibodies, or MuSK antibody, the severity of disease affect the decision of preforming the thymectomy. Historically thymectomy was preformed via sternotomy associated with significant morbidity. Advancement in the minimally invasive approaches to thymic resection has led to more acceptance of thymectomy in the management of MG. Among these approaches, robotic thymectomy is gaining popularity across the globe due to the unique advantages of the robotic platform like 3D visibility, enhanced dexterity, and wrist like articulating movements of instruments. This has led to less post-operative pain and morbidity; faster recovery and shorter hospital stay. Successful treatment of MG requires a multi-modality approach, which has led to the formation of MG teams in most academic centers, comprising of a specialist neurologist, intensivist, and thoracic surgeon. In this article, we describe the techniques and outcomes of the robotic thymectomy for MG.

Examination on the necessity of pericardial fat tissue resection in extended thymectomy for myasthenia gravis

Background

Extended thymectomy with pericardial fat tissue resection has been a mainstay in the treatment for myasthenia gravies (MG), but few studies have examined the necessity of the pericardial fat tissue resection in extended thymectomy.

Methods

We pathologically examined the distribution of germinal centers in the resected thymus including the thymus-surrounding fat tissue. Patients who underwent extended thymectomy using subxiphoid thoracoscopy for generalized MG or thymoma with anti-acetylcholine receptor antibody (anti-AchR Ab) positivity from March 2015 to January 2021 were included in this study.

Results

A total of 20 patients underwent extended thymectomy (generalized nonthymomatous MG, n=5; generalized MG with thymoma, n=6; thymoma with anti-AchR Ab positivity, n=9). The resected specimens were divided to 6 parts and were pathologically examined to investigate the distribution of the geminal centers in all lesions. The number and distribution of germinal centers in the thymus varied depending on the patient, and no germinal centers were identified in the right or left pericardial fat tissues.

Conclusions

It is necessary to resect the pericardial fat tissue in patients whose preoperative images show the presence of pericardial fat tissue hyperplasia or ectopic thymoma. However, extensive pericardial fat tissue resection might not be necessary for all MG patients who undergo extended thymectomy with opening of the bilateral pleural by video-assisted or robot-assisted thoracoscopic surgery (RATS) via a subxiphoid approach.

Evaluation of extended thymectomy approaches based on residual fat tissue

OBJECTIVES

This study analysed the patterns of extraction ranges, characteristics, advantages and disadvantages of median sternotomy (MS) and subxiphoid (SX) approaches for extended thymectomy.

METHODS

This study included patients with anterior mediastinum tumour and myasthenia gravis who underwent extended thymectomy at our institution between 2015 and 2018. There were 5 MS and 6 SX extended thymectomy surgeries with the VINCENT software. On preoperative computed tomography, the thymus area and fat tissue surrounding the thymus, which were planned for extraction, were traced using VINCENT (Ver. 4.0). We then constructed three-dimensional images and calculated the volumes. Evaluation of the extended thymectomy approach based on the residual fat tissue was required to determine the area of extended thymectomy.

RESULTS

No significant differences in operation time (min) [SX: 197.3 ± 34.0, MS: 206.6 ± 91.4, drainage duration (days), SX: 2.2 ± 1.0, MS: 2.2 ± 0.4, hospital stay (days), SX: 11.8 ± 1.2, MS: 13.4 ± 2.1, residual rate (%), SX: 29.9 ± 17.5, MS: 58.7 ± 18.0 (P = 0.0519)] were observed between the 2 groups. Bleeding was significantly lower for SX than for MS. The residual rate was lower for SX than for MS.

CONCLUSIONS

Considering the amount of the residual fat tissue, the SX approach allows an adequate dissection area for extended thymectomy compared with the MS approach.

Role of thymus on prognosis of myasthenia gravis in Turkish population

OBJECTIVE:

Myasthenia gravis (MG) is an autoimmune disease that may cause a disorder in transmission at the neuromuscular junction. Antibodies directed against acetylcholine receptors are responsible. The thymus is the place that that production of these antibodies mainly occurs. The thymus gland abnormalities and abnormal production of these antibodies are associated with MG. Consequently, thymectomy is a common treatment for MG. The nature of the disease makes it difficult to plan prospective, controlled trials; therefore, there is no current consensus among clinicians on a single algorithm of treatment, and the approach is frequently based on the observations and experiences of experts. The contributions to the literature largely consist of retrospective studies examining an approach to treatment and the effects of thymectomy on prognosis. In this retrospective study, evaluation of Turkish patients with myasthenia gravis was carried out for the importance of thymectomy and effects on prognosis.

METHODS:

In this study, 93 patients with myasthenia gravis whose followed up at Neuromuscular outpatient clinic between 1998–2018 were evaluated retrospectively. Type of disease, antibody status, treatment, thymectomy, thymus pathology and prognosis were assessed.

RESULTS:

Thymectomy had been a positive effect on the prognosis of the disease independent of the duration of disease and thymic pathology. The best results had been obtained with early thymectomy with short disease duration, younger age and patients with thymic hyperplasia. Success of therapy was limited with thymoma. With advanced age need for thymectomy was decreased.

CONCLUSION:

In the present study, evaluation of 93 patients with myasthenia gravis was done retrospectively and it was concluded that thymectomy had a positive effect on prognosis, especially in young patients when performed as early as possible. The most successful results were obtained in cases with thymic hyperplasia.

Subxiphoid robotic extended thymectomy - The first Indian report

Background

Minimally invasive thymectomy is fast becoming the preferred approach for myasthenia gravis and non-invasive thymoma. The most commonly employed approach for minimally invasive thymectomy is the lateral thoracic approach. Safe achievement of radical resection requires adequate visualisation of both the phrenic nerves along their entire course. In our experience, such visualisation is rather difficult with unilateral transthoracic approaches. We herein describe our technique and initial experience of 25 cases with subxiphoid robotic thymectomy (SRT) for myasthenia gravis with or without thymoma. To the best of our knowledge, this is the first such report from India.

Subjects and Methods

We retrospectively analysed data of patients who underwent SRT at our centre from June 2017 to September 2018. Twenty-five consecutive patients were analysed, and demographic data, total duration of the procedure, console time, blood transfusion requirement, duration of chest drainage, length of hospital stay, pain score on post-operative day (POD) 1 and day of discharge and post-operative morbidity and mortality within 90 days were recorded.

Results

A total of 25 patients underwent SRT. All our patients had myasthenia gravis with 4 of them having thymoma. There were 11 males and 14 females with mean age of 29.30 years (range 23-48). The mean console time was 102.85 min (range 88-120) while the mean total operative time was 199.14 (range 180-220). On first POD 1, visual analogue scale score average was 5, and at discharge, it was 2. There was no 30-day or 90-day mortality. All cases of thymoma had a complete R0 resection.

Conclusion

Our experience suggests that subxiphoid approach offers a good operative view of the thymus in cervical region along with easy identification of bilateral phrenic nerves. Thus, SRT can be performed safely with comparable results.

Unraveling the role of ectopic thymic tissue in patients undergoing thymectomy for myasthenia gravis

Extended thymectomy has been considered the goal of surgery for myasthenia gravis (MG) mainly due to the existence of ectopic thymic tissue. Recently, ectopic thymic tissue has attracted increasing attention in patients with MG following thymectomy. However, the specific role of ectopic thymic tissue in patients with MG is still under debate. A systematic search of the literature was performed on PubMed and Medline according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISM) statement. Studies evaluating the rate of ectopic thymic tissue in patients with MG with or without thymoma were included. Extraction was performed for all eligible studies and the rate of ectopic thymic tissue at common locations was calculated. Eighteen out of fifty-nine studies were eligible for inclusion, of which ten studies reported the common locations of ectopic thymic tissue in mediastinal fat. Of these ten studies, the presence of ectopic thymic tissue was investigated in different anatomical locations in 882 patients, of whom, 509 patients (58%) have at least one positive location with the most common ones being anterior mediastinal fat, pericardiophrenic angles, aortopulmonary window, cervical region (pretracheal fat) and lateral to phrenic nerves. On the other hand, nine studies analyzed the influence of the presence of ectopic thymic tissue on the clinical outcomes of MG patients. Of these, six found that the presence of ectopic thymic tissue in MG patients is a significant predictor of poor outcome after thymectomy, however, the other three did not find a significance. Altogether, ectopic thymic tissue is likely to present in more than a half of patients undergoing thymectomy for MG. Besides, MG patients who have ectopic thymic tissue after thymectomy do not seem to have as good outcome as those who have not.

[Ectopic thymic tissue and ectopic thymic tumors]

Ectopic thymic tissue outside its core position in the antero-superior mediastinum is quite common owing to the complexity of embryonal thymus development, whereby reported prevalence values (1 to 90%) are heavily dependent on the method of investigation and the intensity of the workup. The debated prevalence and relevance of ectopic thymic tissue and its accessibility underlie the ongoing discussion whether modern, minimally invasive thymectomy strategies can match the proven benefit of the radical transsternal thymectomy procedure for the treatment of Myasthenia gravis. In this context, the following article covers the etiology, prevalence, and location of normal-looking, reactive, and neoplastic ectopic thymic tissue. Furthermore, ectopic tissues and tumors inside or adjacent to the thymus are mentioned.

Surgical Approaches to Myasthenia Gravis: Perspective of Anatomy and Radicality in Surgery

The effectiveness of thymectomy for nonthymomatous myasthenia gravis is analyzed with regard to extensiveness of removal of the adipose tissue of the mediastinum and the lower neck region with various techniques of thymectomy. The approach necessary to achieve maximal radicality must include access to both pleural cavity and the lower neck area up to the thyroid gland. Surgical techniques include extended transsternal approach, which might be combined with separate transcervical incision, bilateral videothoracoscopic (VATS) approach combined with transcervical incision, and extended subxiphoid approach, either uniportal or combined with bilateral VATS. Anatomic aspects of maximally extensive thymectomy are described in detail.

Results of Robotic Thymectomy Performed in Myasthenia Gravis Patients Older Than 60 Years at Onset

BACKGROUND

Data are limited on the safety and efficacy of robotic thymectomy in patients with myasthenia gravis (MG) older than 60 years at onset.

METHODS

Patients older than 60 years at MG onset who underwent robotic thymectomy in Charite Universitaetsmedizin Berlin between 2003 and 2017 were potentially eligible for inclusion. The main outcomes were perioperative complications and clinical outcome according to the Myasthenia Gravis Foundation of America Post-Intervention Status.

RESULTS

Sixty-eight (25 women, 43 men) of 580 patients with MG who underwent robotic thymectomy were eligible for perioperative analyses (median age at MG onset 67 years, range: 61 to 85 years). The perioperative morbidity rate was 13.2%, and the only perioperative death was due to aortic dissection. Fifty-one patients were available for further analysis with a median follow-up time of 60 months (range: 12 to 263 months). The complete stable remission rate was 7.8%, the improvement rate was 68.6%, and the overall mortality rate was 11.8%. Compared with preoperative use, the mean daily dose of corticosteroid agents was significantly reduced at the last follow-up (17.6 ± 23.6 mg versus 2.6 ± 6.1 mg, p = 0.0001) without increased use of azathioprine (35.9 ± 61.9 mg versus 42.7 ± 59 mg, p = 0.427). After excluding 2 patients seronegative for the anti-acetylcholine receptor antibody, 10 of 49 seropositive patients achieved "good outcome" (including four complete stable remissions, three pharmacologic remissions, and three minimal manifestations 0) which was predicted by being free of concomitant disease (odds ratio 7.307, 95% confidence interval: 1.188 to 44.937, p = 0.032) and Myasthenia Gravis Foundation of America classification I before thymectomy (odds ratio 6.696, 95% confidence interval: 1.259 to 35.620, p = 0.026).

CONCLUSIONS

Robotic thymectomy seems to be safe and effective in patients with MG older than 60 years at onset with a statistically significant steroid-sparing effect.

A Neurologist's Perspective on Thymectomy for Myasthenia Gravis: Current Perspective and Future Trials

The first randomized blinded study of thymectomy in nonthymomatous myasthenia gravis was designed to answer 3 questions: does the combination of prednisone and removal of the thymus gland via extended transsternal thymectomy after 3 years compared with an identical dosing protocol of prednisone alone (1) lead to better disease status for generalized MG patients with antiacetylcholine receptor antibodies, (2) reduce their prednisone requirements, and/or (3) reduce the side-effect burden from medications used to treat the disease? The study demonstrated that thymectomy confers these benefits for patients and sets the stage for inquiries into the benefits of less-invasive approaches to thymic resection.

Predictive value of the thymofatty specimen weight index in outcomes of extended thymectomy due to non-thymomatous myasthenia gravis

OBJECTIVES

To evaluate the predictive value of the intraoperative thymofatty specimen weight (TFSW) index on predicting the prognosis of extended thymectomy (ET) for non-thymomatous myasthenia gravis.

METHODS

This is a prospective non-interventional study in which patients who underwent ET between January 2012 and June 2015 were enrolled. Resected thymus and surrounding adipose tissues were weighed using an electronic scale intraoperatively and adjusted to the body surface area (BSA) to calculate the TFSW index. The primary end point was defined as complete stable remission (CSR) according to the Myasthenia Gravis Foundation of America (MGFA) guidelines.

RESULTS

One hundred and eighteen patients who completed postoperative follow-up were included in this study. After a mean follow-up period of 44 months, 68 (57.6%) patients reached clinical CSR. The MGFA class, histopathology and TFSW index were associated with a postoperative CSR in univariate analysis. When the Cox hazard multiple regression model was used, the TFSW index was found to be an independent predictor for CSR (hazard ratio 2.056; 95% confidence interval 1.182-3.576). Based on ROC analysis, an optimal TFSW index cut-off value (35.9 g/m2) with the highest sensitivity and specificity was determined.

CONCLUSIONS

The TFSW index is an important independent predictor for mid-term CSR after ET in non-thymomatous myasthenia gravis patients. During the ET surgery, every effort should be made to take a tissue specimen with a TFSW index more than 35.9 g/m2.

Onset and Evolution of Clinically Apparent Myasthenia Gravis After Resection of Non-myasthenic Thymomas

Patients with thymoma and without clinical or electromyographical myasthenic signs may occasionally develop myasthenia several years after thymectomy. Hereby, we investigated the predictors and the evolution of this peculiar disease. We performed a retrospective analysis in 104 consecutive patients who underwent thymectomy between 1987 and 2013 for thymoma without clinical or electromyographic signs of myasthenia gravis. Predictors of post-thymectomy onset of myasthenia gravis were investigated with univariate time-to-disease analysis. Evolution of myasthenia was analyzed with time-to-regression analysis. Eight patients developed late myasthenia gravis after a median period of 33 months from thymectomy. No significant correlation was found for age, gender, Masaoka's stage, and World Health Organization histology. Only high preoperative serum acetylcholine-receptor antibodies titer (>0.3 nmol/L) was significantly associated with post-thymectomy myasthenia gravis at univariate time-to-disease (P = 0.003) analysis. Positron emission tomography was always performed in high-titer patients, and increased metabolic activity was detected in 4 of these patients. Surgical treatment through redo-sternotomy or video-assisted thoracoscopy was performed in these last cases with a remission in all patients after 12, 24, 32 and 48 months, respectively. No patient under medical treatment has yet developed a complete remission. In our study the presence of preoperative high-level serum acetylcholine receptor antibodies was the only factor significantly associated with the development of post-thymectomy myasthenia gravis. The persistence of residual islet of ectopic thymic tissue was one of the causes of the onset of myasthenia and its surgical removal was successful.

Definitions and standard indications of minimally-invasive techniques in thymic surgery

BACKGROUND

The minimally invasive thoracic procedures are those performed through the intercostal, subxiphoid, subcostal or transcervical incisions. In most of these procedures (with exception of some transcervical procedures) the video-assisted thoracic surgery (VATS) technique is used for performance of an operation under guidance of a video monitor.

METHODS

According to the definition the minimally invasive procedures do not include the sternal manubriotomy (upper sternal split), transverse sternotomy and subcutaneous longitudinal sternotomy. Currently, a minimally invasive extended thymectomy became a widespread procedure advised for nonthymomatous myasthenia gravis (MG) and early-stage thymomas. The definition of an extended thymectomy is a removal of the whole thymus with the surrounding adipose tissue. Instead of the term "extended thymectomy" some authors recommended a term "complete thymectomy", which means total removal of the whole thymus, without the adjacent fatty tissue.

RESULTS

There are a lot of doubts about the definition of extended thymectomy. There have been no prospective randomized trials comparing the transsternal and minimally invasive approaches for MG or thymomas. Possible scenarios for such trials are analyzed in this paper.

CONCLUSIONS

There are several issues of a minimally invasive thymectomy for MG and thymomas necessitating further clarifications.

Randomized Trial of Thymectomy in Myasthenia Gravis

BACKGROUND

Thymectomy has been a mainstay in the treatment of myasthenia gravis, but there is no conclusive evidence of its benefit. We conducted a multicenter, randomized trial comparing thymectomy plus prednisone with prednisone alone.

METHODS

We compared extended transsternal thymectomy plus alternate-day prednisone with alternate-day prednisone alone. Patients 18 to 65 years of age who had generalized nonthymomatous myasthenia gravis with a disease duration of less than 5 years were included if they had Myasthenia Gravis Foundation of America clinical class II to IV disease (on a scale from I to V, with higher classes indicating more severe disease) and elevated circulating concentrations of acetylcholine-receptor antibody. The primary outcomes were the time-weighted average Quantitative Myasthenia Gravis score (on a scale from 0 to 39, with higher scores indicating more severe disease) over a 3-year period, as assessed by means of blinded rating, and the time-weighted average required dose of prednisone over a 3-year period.

RESULTS

A total of 126 patients underwent randomization between 2006 and 2012 at 36 sites. Patients who underwent thymectomy had a lower time-weighted average Quantitative Myasthenia Gravis score over a 3-year period than those who received prednisone alone (6.15 vs. 8.99, P<0.001); patients in the thymectomy group also had a lower average requirement for alternate-day prednisone (44 mg vs. 60 mg, P<0.001). Fewer patients in the thymectomy group than in the prednisone-only group required immunosuppression with azathioprine (17% vs. 48%, P<0.001) or were hospitalized for exacerbations (9% vs. 37%, P<0.001). The number of patients with treatment-associated complications did not differ significantly between groups (P=0.73), but patients in the thymectomy group had fewer treatment-associated symptoms related to immunosuppressive medications (P<0.001) and lower distress levels related to symptoms (P=0.003).

CONCLUSIONS

Thymectomy improved clinical outcomes over a 3-year period in patients with nonthymomatous myasthenia gravis. (Funded by the National Institute of Neurological Disorders and Stroke and others; MGTX ClinicalTrials.gov number, NCT00294658.).

Clinical Outcomes of Myasthenia Gravis with Thymoma and Thymic Hyperplasia Undergoing Extended Transsternal Thymectomy: A Single-Center Experience

BACKGROUND

Despite the widespread use of thymectomy in myasthenia gravis (MG) patients, it has remained controversial as to whether this procedure is of a similar efficacy and clinical outcome among MG patients with thymoma and thymic hyperplasia.

AIM

We sought to determine the long-term clinical outcomes of MG patients who received extended transsternal thymectomy associated with pyridostigmine and prednisolone postoperatively.

MATERIALS AND METHODS

In a retrospective study from January 1999 to December 2013, MG patients who underwent thymectomy were followed up. Out of 41 MG patients admitted in our center, 25 patients had undergone thymectomy adjunctive to pyridostigmine and prednisolone therapy postoperatively. The primary endpoints included improvement in individual diplopia, ptosis, dysphagia, dysarthria, dyspnea, and limb weakness. In addition, according to the MG Foundation of America (MGFA) criteria, response to therapy was defined as complete stable remission (CSR), pharmacologic remission (PR), and minimal manifestation (MM) as secondary endpoints.

RESULTS

Majority of the patients were male (60%) and the mean age of the patients was 32.2 ± 13.9 years. Fifteen (60%) and 10 patients (40%) had thymoma and thymic hyperplasia, respectively. All the patients were followed up during a mean period of of 86.9 ± 50.3 months (minimum 10 months and maximum 168 months). The rates of CSR, PR, and MM were comparable between the thymoma and thymic hyperplasia groups (P = 0.584). Based on the Kaplan Meier analysis, the probabilities of CSR, PR, and MM were not significantly different between patients with thymoma and thymic hyperplasia.

CONCLUSION

The extended transsternal thymectomy, along with the postoperative regimen of pyridostigmine and prednisolone was associated with a high rate of clinical improvement among MG patients with thymoma or thymic hyperplasia.

Thymus pathology observed in the MGTX trial

The MGTX trial is the first prospective, randomized clinical trial that aims to evaluate the impact of extended transsternal thymectomy on myasthenic symptoms, prednisone requirements, and quality of life in patients with nonthymomatous, anti-acetylcholine receptor autoantibody-positive myasthenia gravis (MG). Here, we give an overview of the rationale of thymectomy and the standardized macroscopic and histopathological work-up of thymectomy specimens as fixed in MGTX standard operating procedures, including the grading of thymic lymphofollicular hyperplasia and the morphometric strategy to assess thymic involution.

Management of juvenile myasthenia gravis

Juvenile myasthenia gravis is an uncommon autoimmune disorder. Its management is not standardized. Juvenile myasthenia gravis is pathophysiologically similar to myasthenia gravis in adults. However, a number of significant particularities related to race, age at onset, severity, and antibody status complicate the management. We summarize the unique clinical features of juvenile myasthenia gravis and review the therapeutic options.

Surgical and neurologic outcomes after robotic thymectomy in 100 consecutive patients with myasthenia gravis

OBJECTIVE

Thymectomy is a well-defined therapeutic option for patients with myasthenia gravis; however, controversies still exist about the surgical approach, indication, and timing for surgery. We reviewed our experience reporting surgical and neurologic results after robotic thymectomy in patients with myasthenia gravis.

METHODS

Between 2002 and 2010, 100 patients (74 female and 26 male; median age, 37 years) underwent left-sided robotic thymectomy using the da Vinci robotic system (Intuitive Surgical, Inc, Sunnyvale, Calif). The Myasthenia Gravis Foundation of America classification was adopted for pre- and postoperative evaluation. Preoperative Myasthenia Gravis Foundation of America class was I in 10% of patients, II in 35% of patients, III in 39% of patients, and IV in 16% of patients.

RESULTS

Median operative time was 120 (60-300) minutes. No death or intraoperative complications occurred. Postoperative complications were observed in 6 patients (6%) (bleeding requiring blood transfusions in 3, chylothorax in 1, fever in 1, and myasthenic crisis in 1). Median hospital stay was 3 days (range, 2-14 days). Histologic analysis revealed 76 patients (76%) with hyperplasia, 7 patients (7%) with atrophy, 8 patients (8%) with small thymomas, and 9 patients (9%) with normal thymus; ectopic thymic tissue was found in 26 patients (26%). Clinical follow-up showed a 5-year probability of complete stable remission and overall improvement of 28.5% and 87.5%. Remission was significantly associated with preoperative I to II Myasthenia Gravis Foundation of America class (P = .02). A significant improvement rate was found in Myasthenia Gravis Foundation of America class I to II (P = .03) and AbAchR+ (P = .04). A high percentage of patients interrupted or reduced their medications.

CONCLUSIONS

Robotic thymectomy is a safe and effective procedure. We observed a neurologic benefit in a great number of patients. A better clinical outcome was obtained in patients with early Myasthenia Gravis Foundation of America class.

Single-institution experience on robot-assisted thoracoscopic operations for mediastinal diseases

OBJECTIVE

: After the introduction of video-assisted thoracoscopic surgery 20 years ago, the minimally invasive techniques in thoracic surgery have found a growing application. The recent introduction of robotic technology has increased the potentiality of thoracoscopic technique leading to an expansion of indications and applications, particularly for the management of mediastinal diseases. We reviewed our experience in robot-assisted thoracoscopic resection of benign and malignant mediastinal diseases.

METHODS

: Between 2002 and 2010, 108 patients (79 women and 29 men; median age 38 y) underwent robot-assisted thoracoscopy using the "da Vinci" robotic system for several mediastinal diseases. There were 100 thymectomies, 3 resections of paravertebral tumors, 1 thymic cyst, 1 ectopic goitre, 1 ectopic mediastinal parathyroidectomy, 1 thymic carcinoid, and 1 foregut cyst. Ninety-five (87.9%) patients were affected by myasthenia gravis.

RESULTS

: All procedures were completed successfully using the da Vinci robot; no open conversions were required, but in three (2.8%) cases, a fourth access was added. There was no surgical mortality; four (3.6%) patients had postoperative complications (two hemothorax, one chylothorax, and one fever) treated conservatively. Median operation time was 120 (range 60-300) minutes and median hospitalization was 3 (range 2-14) days. Global benefit rate for patients with myasthenia gravis reached the value of 93.4% with progressive improvement over years.

CONCLUSIONS

: Several mediastinal operations may be feasible by using a robot-aided thoracoscopic approach. The technical innovations offered by robotic instrumentation make all procedures safer and easier when compared with standard thoracoscopic approach, with particular reference for application in mediastinal field.

Extended transsternal thymectomy for the treatment of ocular myasthenia gravis

BACKGROUND

The optimal treatment for ocular myasthenia gravis (OMG) remains controversial. We conducted a review of the long-term clinical outcomes of Chinese patients with OMG after extended transsternal thymectomy (ETT) to determine the efficacy of this procedure as a treatment for OMG.

METHODS

We reviewed the cases of 115 consecutive patients with OMG who underwent ETT at our Myasthenia Gravis Research Center between January 2006 and December 2008. Extended transsternal thymectomy was done in patients who had thymoma, resistance to pyridostigmine therapy, or relapse after immunosuppressive therapy. The patients' postoperative responses were defined as strict complete remission (SCR), consisting of an asymptomatic status without medication for more than 12 months; general complete remission (GCR), consisting of an asymptomatic status with low-dose single-drug therapy or without medication for more than 12 months; or improvement, consisting of fewer symptoms or less of a need for medication than before surgery.

RESULTS

The overall complication rate was 7.8%. None of the patients experienced a myasthenic crisis, progression to generalized myasthenia gravis, or mortality. Hyperplasia of the thymus was present in 106 of the 115 patients (92.2%). Among 110 patients on whom follow-up was done postoperatively, 29 (26.4%) were in SCR, 64 (58.2%) showed improvement, 7 (6.4%) remained unchanged, and 10 (9.1%) had a worsening of their conditions. Kaplan-Meier analysis revealed rates of GCR of 41.8% at 24 months and 47.3% at 48 months after surgery, and rates of SCR of 24.5% at 24 months and 26.4% at 48 months. Both univariate analysis and multivariate Cox regression analysis revealed that only preoperative duration of illness was positively associated with GCR (p < 0.001).

CONCLUSIONS

The results of the review indicate that ETT is a safe and effective treatment for OMG, especially in patients with illness of shorter duration.

Myasthenia gravis

OPINION STATEMENT

Treatment of patients with acquired (autoimmune) myasthenia gravis should rely on evidence-based therapeutic choices, taking into account the individual's needs according to disease severity (mild to severe), extent (ocular or generalized), comorbidities (including other autoimmune diseases, infections, thymoma, and pregnancy), age, iatrogenic factors (the risks and benefits of therapy), patient autonomy and quality of life, financial burden to the patient, and associated health care costs. Therapy is aimed at managing symptoms by improving neuromuscular junction transmission (cholinesterase inhibitors) and/or modifying the underlying immunopathogenetic cause of acquired myasthenia gravis via immunosuppression or immunomodulation. Myasthenic patients with operable thymoma should be referred for surgery and closely followed up for tumor recurrence. A concerted international effort is addressing treatment recommendations for thymectomy in myasthenic patients with no radiologic evidence of thymoma who are positive for circulating acetylcholine receptor antibodies. There is a lack of evidence-based treatment guidelines for both acute and long-term management of ocular myasthenia. Acute management of myasthenic crisis requires intensive monitoring of the patient and institution of an efficient and safe treatment such as plasma exchange. Patient education is essential to a comprehensive long-term treatment plan.