[Myasthenia gravis occurring after resection of thymoma]

The aim of this study was to analyses the clinicopathologic features of the patient with myasthenia gravis (MG) occurring after resection of thymoma.

Data of 15 patients were collected. The follow-up range from 8 to 178 (average 76.7) months. A retrospective analysis was performed through comparison with data of all 112 cases without MG, which had not occurred MG during our average 5.5 years follow-up, operated for thymoma in same period. The statistics analysis adopted chi(2) and t test.

(1) According to Masaoka's classification of thymoma, stage I in 7 cases, stage II in 4, stage III in 4. Histologic Bernatz's classification: lymphocyte predominant type in 4, epithelial type in 3, mixed type in 7, unknown in 1. According to Osserman's classification of MG, grade I in 7, IIa in 4, IIb in 3, III in 1. The MG onset times was the postoperative narcotic waking duration-137 (average 33.9) months, and the average remission time was 30.9 (0.5 - 120) months. (2) 4 cases who occur MG as soon as pull up narcotic tube, all adopted nondepolarizing muscular relaxants. (3) MG was discovered in 3 cases (3/67) during postoperative radiotherapy until a average dosage of 36 Gy was received in average 24 days. (4) The tendency of occurring MG following resection was found in female patients with longer duration of disease, mixed type, larger and later stage thymoma as compared with the thymoma group.

The factors including the operation, relatively using overdose relaxation control, choosing unfavorable muscle relaxant and postoperative radiotherapy could induce postoperative MG. An intensive care should be put on the cases with the tendency of occurring postoperative MG.