Effect of thymectomy for thymic atrophy in myasthenia gravis: A retrospective study on 93 patients

[A case of non-thymomatous refractory anti-AChR, Kv1.4 and titin antibodies positive generalized myasthenia gravis successfully treated by extended thymectomy]

A 74-year-old Japanese woman, who had been previously diagnosed as ocular myasthenia gravis (MG), presented to our hospital complaining of dropped head and increased fatiguability while eating. The edrophonium test was positive and decremental response was recorded on repetitive nerve stimulation. Her clinical presentation was compatible with generalized MG, and anti-AChR, Kv1.4 and titin antibodies turned out positive. Contrast enhanced CT scan showed no tumorous lesion such as thymoma. We initiated her treatment with a minimum dose of oral prednisolone. However, her condition got worse even after intravenous immune globulin and experienced myasthenic crisis twice, the former of which led to cardiopulmonary arrest. As she did not respond to traditional treatments, we determined to perform extended thymectomy. The histopathology showed atrophic change but her condition rapidly improved in several days after the operation, and soon she was weaned off the ventilator. Shortly thereafter her symptoms disappeared, followed by the titers of the antibodies above found all markedly decreased. It remains unclear how the atrophic thymus acted on the pathogenesis of refractory generalized MG.

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.

Novel treatment strategies for acetylcholine receptor antibody-positive myasthenia gravis and related disorders

The presence of autoantibodies directed against the muscle nicotinic acetylcholine receptor (AChR) is the most common cause of myasthenia gravis (MG). These antibodies damage the postsynaptic membrane of the neuromuscular junction and cause muscle weakness by depleting AChRs and thus impairing synaptic transmission. As one of the best-characterized antibody-mediated autoimmune diseases, AChR-MG has often served as a reference model for other autoimmune disorders. Classical pharmacological treatments, including broad-spectrum immunosuppressive drugs, are effective in many patients. However, complete remission cannot be achieved in all patients, and 10% of patients do not respond to currently used therapies. This may be attributed to production of autoantibodies by long-lived plasma cells which are resistant to conventional immunosuppressive drugs. Hence, novel therapies specifically targeting plasma cells might be a suitable therapeutic approach for selected patients. Additionally, in order to reduce side effects of broad-spectrum immunosuppression, targeted immunotherapies and symptomatic treatments will be required. This review presents established therapies as well as novel therapeutic approaches for MG and related conditions, with a focus on AChR-MG.

Effects of thymectomy on late-onset non-thymomatous myasthenia gravis: systematic review and meta-analysis

BACKGROUND

The effects of thymectomy on late-onset non-thymomatous myasthenia gravis (NTMG) remain controversial. The objective of this study was to conduct a systematic review in order to answer two questions pertinent to late-onset NTMG: (1) do patients with late-onset NTMG experience the same effects from thymectomy as their early-onset counterparts? (2) Compared with conservative treatment, does thymectomy have any benefits for late-onset NTMG patients?

METHODS

We searched the PubMed, EMBASE, and Cochrane Library databases for studies published from January 1, 1950 to March 10, 2021. Outcomes were measured via clinical stable remission/pharmacological remission (CSR/PR) and improvement rates. We used Stata software to analyze the data.

RESULTS

We ultimately included a total of 12 observational articles representing the best evidence answering the questions of our study objective. Of these, nine studies, which included 896 patients overall (766 early-onset and 230 late-onset), compared postoperative outcomes between early- and late-onset NTMG. The remaining three articles, which included 216 patients (75 in the thymectomy group and 141 in the conservative-treatment group), compared thymectomy with conservative treatment for late-onset NTMG. The early- versus late-onset NTMG studies demonstrated that patients in the former category were 1.95× likelier than their late-onset counterparts to achieve clinical remission (odds ratio [OR] 1.95; 95% confidence interval [CI] 1.39-2.73; I2 = 0%). No difference was seen in improvement or remission + improvement rates between these two groups. When comparing thymectomy with conservative treatments in late-onset NTMG patients, neither did we observe any difference in CSR/PR.

CONCLUSION

We found that late-onset NTMG patients had a lower chance of achieving CSR after thymectomy than early-onset patients. Thymectomy in late-onset NTMG also yielded no benefit to CSR or PR compared with conservative treatments. In late-onset NTMG patients, thymectomy should therefore be performed with caution, and the appropriate cutoff between early- and late-onset MG should be further explored in order to tailor and execute the proper therapeutic strategies.

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.

Effect of thymectomy in elderly patients with non-thymomatous generalized myasthenia gravis

Whether thymectomy is beneficial in elderly patients with myasthenia gravis (MG) is unclear. Thus, we assessed whether conducting thymectomy in MG patients aged ≥ 50 years is beneficial. This retrospective cohort study included patients with MG between 1990 and 2018. Thymectomy and control cohorts were selected from among the population of MG patients with an age at onset of ≥ 45 years and elevated concentrations of acetylcholine-receptor antibodies. Patients with evidence of thymic malignancy were excluded. Of these patients, those who underwent thymectomy at the age of ≥ 50 years were designated as the thymectomy group and those who received only medical treatment were designated as the medical treatment group. We compared the Myasthenia Gravis Foundation of America post-intervention status between the thymectomy and medical treatment groups. Landmark analysis was conducted with the landmark set at 24 months. A total of 34 and 105 patients were classified into the thymectomy and medical treatment groups, respectively. Before landmark analysis, the thymectomy group had a higher cumulative incidence of pharmacologic remission (p = 0.009) and complete stable remission (p = 0.022) than the medical treatment group. After landmark analysis, the thymectomy group had a 2.22-fold (95% confidence interval 1.01-4.80) increased chance of achieving pharmacologic remission compared to the medical treatment group after adjustment for age, sex, and disease severity. No significant difference was observed in the rate of relapse after pharmacological remission between the thymectomy (16.7%) and medical treatment groups (21.4%). In conclusion, thymectomy may have a beneficial effect in elderly patients with non-thymomatous generalized MG.