Factors influencing the outcome of transsternal thymectomy for myasthenia gravis

Background - Thymectomy is one of the current treatment strategies for patients with myasthenia gravis (MG); however, the selection criteria for surgery remain controversial. Methods - The demographic data and the surgical results of 168 patients with MG who underwent transsternal thymectomy from June 1986 to December 2000 were retrospectively reviewed. Follow-up information was obtained by review of the hospital records or telephone contact. The postoperative status of MG was assessed at the interval of 1, 3 and 6 months and then annually. The complete remission rate (CRR) between groups was compared. Results - A total of 168 patients, including 69 male patients and 99 female patients, with a mean age of 38.3 years (range 13-80 years), were analyzed. The symptom duration before operations was from 1 to 312 months with a mean of 33.8 months. Complete follow-up information was obtained on 154 patients (91.6%) with a mean follow-up duration of 98.9 months. Complete remission was achieved in 89 of 154 patients (57.8%) and marked clinical improvement in 47 patients (30.5%). Total improvement rate was 88.3%. Seventeen of 24 patients (70.8%) with ocular MG and 18 of 35 patients (51.4%) with thymoma had reached complete remission during the follow-up period. The CRR increased with each consecutive year and reached the plateau in the fourth postoperative year. There was no surgical mortality. The complication rate was 16.6%. Univariate analysis demonstrated that age < 35 years old (P = 0.0001), symptom duration before operation < 24 months (P = 0.01) and absence of preoperative steroid treatment (P = 0.04) were favorable prognostic factors. Multivariate Cox regression analysis revealed age < 35 years old (odds ratio = 3.645, P = 0.001), symptom duration before operation < 24 months (2.311, P = 0.041) were favorable prognostic factors for patients having transsternal thymectomy. Conclusions - Transsternal thymectomy is feasible in the management of patients with MG at all stages with high improvement rate and low surgical morbidity. Those patients aged 35 years or less at operation, with symptoms developed < 24 months before operation, may benefit more from thymectomy. MG patients with thymoma did as well as patients without thymoma, and 18 of 35 patients with thymoma had reached complete remission during the follow-up period. Thymectomy seems to be beneficial also for ocular MG.