Therapeutic effects of thymectomy in patients with myasthenia gravis

ABSTRACT

Thymectomy is considered as one of the important therapy for patients with myasthenia gravis(MG) for reducing the symptoms and hasting the time of remission. However, the efficacy of thymectomy in previous studies were not in concordant with each others. This study was designed to assess the effects of thymectomy in 84 MG patients. The patients were divided into two groups according to their medications before thymectomy the patients who had been treated with anticholinesterase(ACE group) and the others who had been treated with both anticholinesterase and steroid(steroid group). The outcomes of thymectomy were divided into two group ""success"" and ""failure"". The ""success"" outcomes included the patients with remission or improvements and the ""failure"" outcomes included the patients with improvement by immunosuppressive agents, unimprovement, and death. To find factors which might influence on the prognosis after thymectomy, the following variables were considered for statistics; The onset age of MG, gender, myasthenic crisis before operation, the clinical symptoms at the time of operation, and the pathologic findings of thymus. The results were as follows. Sixty-six patients were included in ACE group and 18 in steroid group. The success were occurred in 37 patients among ACE group(56%) and in 8 patients among steroid group(44.4%). In ACE group, the success more frequently occurred in the patients with thymic follicular hyperplasia(79.3%) than in those with thymoma(36%), and normal or atrophic thymus(41.7%). The Patients who had mild clinical symptoms at the operation also showed higher success rate. However, gender, the age of onset, and the presence of myasthenic cirsis before the operation did not influences on the results of the operation. In steroid group, the success rate was higher in the patients with shorter duration of steroid treatment before thymectomy(< 6 month) and follicular hyperplasia. In addition, the immunosuppressive treatments also gave symptomatic improvements in most patients with failure outcomes after thymectomy. In conclusion, thymectomy demonstrated beneficial effects in about half of MG patients. Follicular hyperplasia and mild symptoms at the operation were considered to be factors for predicting better results after thymectomy. Our findings also suggest that the longstanding steroid treatment before thymectomy may negatively affect on the successful thymectomy, especially on remission.