Factors predicting surgical outcome of thymectomy in myasthenia gravis: A 16-year experience

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.

Prevalence and risk factors of myasthenia gravis recurrence post-thymectomy

Objectives:

To evaluate the prevalence and the factors associated with recurrence of myasthenia gravis following thymectomy.

Methods:

Six electronic databases which reported on recurrence of myasthenia gravis following thymectomy and/or its risk factors from 1985 to 2018 were searched. Summary prevalence and risk values obtained based on the random effect models were reported.

Results:

Seventy (70) papers containing 7,287 individuals with myasthenia gravis who received thymectomy as part of their management were retrieved. The patients had a mean follow-up of 4.65 years post-thymectomy. The prevalence of myasthenia gravis recurrence post-thymectomy was 18.0% (95% CI 14.7–22.0%; 1865/7287). Evident heterogeneity was observed (I²=93.6%; p<0.001). Recurrence rate was insignificantly higher in male compared with female patients (31.3 vs. 23.8%; p=0.104). Pooled recurrence rates for thymomatous (33.3%) was higher than the rate among non-thymomatous (20.8%) myasthenia gravis patients (Q=4.19, p=0.041). Risk factors for recurrence include older age, male sex, disease severity, having thymomatous myasthenia gravis, longer duration of the myasthenia gravis before surgery, and having an ectopic thymic tissue.

Conclusion:

A fifth of individuals with myasthenia gravis experience recurrence after thymectomy. Closer monitoring should be given to at-risk patients and further studies are needed to understand interventions to address these risks.

Surgical and Neurological Outcome of Minimally Invasive Thymectomy in Patients With Myasthenia Gravis: An Experience of 100 Cases Over 6 Years at a Tertiary Care Center in North India

BACKGROUND

Minimally invasive thymectomy (MIT) is emerging as an effective alternative to open thymectomy in the management of patients with myasthenia gravis (MG). The primary objective of our study is to assess the surgical and neurological outcome of MIT in patients with MG.

MATERIALS AND METHODS

It is a retrospective evaluation of prospectively collected data of 100 patients with MG, who underwent MIT from April 2012 to January 2018 at a tertiary care center in India. Surgical outcome was assessed for success of minimal invasive approach, conversion, perioperative morbidity, and postoperative hospital course. Neurological outcome was assessed, after at least 1 year of follow-up, according to Myasthenia Gravis Foundation of America postintervention status. Factors predicting complete stable remission (CSR) were evaluated.

RESULTS

MIT was successfully performed in 98% patients with 2% conversion. There was no mortality. Overall, 10% of patients had perioperative morbidity with 5% having exacerbation of neurological symptoms. Two of these needed postoperative ventilation, whereas 3 recovered on conservative treatment. Median operative time and hospital stay were 140 minutes and 3 days, respectively. At a median follow-up of 47 months, CSR was seen in 20% with improvement in 73.3%. Overall, 63% patients were taken off steroids and patients requiring 3 drugs decreased by 70.7%. There was significant reduction in the dosage of pyridostigmine (P<0.001), prednisolone (P<0.001), and azathioprine (P=0.002) after thymectomy. Milder disease (Myasthenia Gravis Foundation of America class 1 and 2) predicted CSR on multivariate analysis.

CONCLUSIONS

MIT is a safe and effective procedure that leads to improvement in neurological status with significant reduction in number and dosage of medications after thymectomy. Mild disease predicts CSR.

Assessment of pre and post-thymectomy myasthenia gravis

OBJECTIVE

To evaluate transcervical and transsternal thymectomy benefits in large myasthenia gravis (MG) cohort.

METHOD

We retrospectively evaluated MG patients (n = 184) who had undergone thymectomy between 2004 and 2015 at National Institute of Mental Health and Neurosciences, Bangalore (India). Myasthenia gravis foundation of America guidelines were followed to assess clinical outcome. Anti-acetylcholine receptors (AChR) antibodies, repetitive nerve stimulation (RNS) and Neostigmine tests were performed at pre and post-thymectomy stage.

RESULTS

Most of the patients were fell under MG grade IIA (82 of 184, 44.56%) and grade IIB (61 of 184, 33.15%). Thymoma and thymic hyperplasia was established in 64 (34.78%) and 89 (48.37%) patients respectively. Other thymic abnormalities such thymic atrophy, cysts and lipoma were established in 31 (16.85%) patients. MG patients were treated either with transcervical (n = 79) or (n = 105) transsternal thymectomy. At the pre-thymectomy stage, the majority of the patients were positive for anti-AChR antibodies (179 of 184, 97.28%), RNS (170 of 184, 92.4%), and Neostigmine (175 of 184, 95.11%). At the post-thymectomy stage, a significant reduction observed in anti-AChR antibodies positivity (p < 0.022) and RNS positivity (p < 0.015). Overall, benefits were observed in 61.41% (113 of 184) of patients. Clinical benefits (complete stable remission, pharmacological remission, minimal manifestation, and improvement) of transcervical and transsternal thymectomy observed in 69.62% (55 of 79) and 55.24% (58 of 105) of patients respectively. MG patients with thymoma showed the least improvement compared to thymic hyperplasia.

DISCUSSION

Transcervical and transsternal thymectomy showed clinical benefits, however, there was no significant difference between them.

Clinical Profile and Outcome of Postthymectomy versus Non-Thymectomy Myasthenia Gravis Patients in the Philippine General Hospital: A 6-Year Retrospective Study

Background

Myasthenia gravis is an autoimmune neuromuscular disorder characterized by the production of abnormal autoantibodies directed against the receptors present in the neuromuscular junction. It has been the standard practice to offer thymectomy in all generalized myasthenia gravis patients despite the lack of robust evidence.

Objectives

The objectives of this study are to describe the clinical profile and differentiate the clinical outcomes of thymectomy versus non-thymectomy and thymomatous versus non-thymomatous myasthenia gravis patients in the Philippine General Hospital.

Methodology

Between 2009 and 2014, a total of 69 postthymectomy and 16 non-thymectomy patient records were successfully retrieved. The demographic characteristics, surgical approach, and histopathologic results were obtained. The clinical outcome after 6 months or 1 year-follow-up was also determined and grouped according to the following: (1) complete remission, (2) pharmacological remission, (3) no clinical change, (4) worsening symptoms, and (5) mortality.

Results

Majority of the patients were females (68.0%) with a mean age of 39.8 years and a mean duration of myasthenic symptoms of 21 months. Using the Myasthenia Gravis Foundation of America classification, 54.1% of patients fell under Class II and 48.2% of them presented with generalized weakness. In this study, 60.8% of postthymectomy myasthenia gravis patients had either complete remission or pharmacologic remission compared with 12.5% among non-thymectomy patients (p-value <0.001). No significant difference in the clinical outcome was found between thymomatous and non-thymomatous myasthenia gravis after thymectomy (p-value = 0.29).

Conclusion

This study showed that both thymomatous and non-thymomatous myasthenia gravis patients who underwent thymectomy had a higher incidence of complete stable remission and pharmacologic remission as compared with myasthenia gravis patients who did not undergo thymectomy.

Eight-year follow-up of patients with myasthenia gravis after thymectomy

PURPOSE

To depict the long-term outcome of patients with myasthenia gravis after thymectomy in combination with immunotherapy, and the factors that may potentially affect the outcome.

METHODS

The 306 patients with myasthenia gravis who underwent extended thymectomy from January 1984 to December 2011 at Tongji Hospital were retrospectively evaluated.

RESULTS

The patients consisted of 174 cases with thymoma and 132 cases without thymoma. Pharmaceutical treatment was tailored for each case during follow-up. Nine patients with thymomatous myasthenia gravis died during the perioperative period, and 297 patients were followed for 8.6 years. By their latest visits, 241 patients (81.1%) gained satisfactory efficacy, 24 cases died (8.1%), and 32 cases (10.8%) remained unchanged or deteriorated. Favorable factors for satisfactory efficacy included the presence of ocular myasthenia gravis before operation, no presence of thymoma, and lack of concomitant diseases. It is interesting to mention that, patients with non-thymomatous myasthenia gravis obtained significantly higher rates of complete stable remission and clinical remission than the patients with thymomatous myasthenia gravis.

CONCLUSIONS

Extended thymectomy combined with immunotherapy is a preferred treatment with a satisfactory long-term remission rate. Patients with non-thymomatous myasthenia gravis have a much more promising prognosis than the patients with thymomatous myasthenia gravis. However, appropriate caution must be taken to discontinue pharmaceutical therapy as relapse remains a major concern after a patient who has already undergone thymectomy becomes symptom-free.

Overview of myasthenia gravis

Myasthenia gravis is an antibody-mediated disorder of neuromuscular transmission that is characterized by weakness and fatigue of voluntary muscles. Weakness may be ocular, bulbar, or generalized. Diagnostic evaluation of patients consists of bedside assessment, antibody testing, and electrophysiologic studies. Various therapeutic options are available, which consist of anticholinesterase inhibitors for symptomatic management, immunosuppressive agents as maintenance therapy, and thymectomy. Plasmapheresis and intravenous immunoglobulin are used in patients in crisis or those with rapidly worsening or refractory symptoms. In our article, we elaborate on key aspects of the epidemiology, pathogenesis, diagnostic evaluation, and therapeutic options for patients with myasthenia gravis.