Thymectomy for non-thymomatous myasthenia gravis: a comparison of surgical methods and analysis of prognostic factors.

OBJECTIVE While thymectomy is an accepted treatment for myasthenia gravis (MG), video-assisted thoracoscopic surgery (VATS) thymectomy has recently become a popular surgical treatment, especially for non-thymomatous MG (NTMG). This study aims to compare the results of VATS thymectomy and trans-sternal thymectomy, and identify prognostic factors in NTMG patients after thymectomy. METHODS A 10-year retrospective review (January 1995 to December 2004) of 60 consecutive thymectomies (22 trans-sternal thymectomies and 38 VATS thymectomies) of NTMG patients performed in a university teaching hospital was undertaken. RESULTS There were 43 female patients and 17 male patients with a median MG-onset age of 25 years (range: 5-78 years). Median follow-up time was 44 months. VATS thymectomy patients had a shorter hospital stay than the trans-sternal thymectomy patients (5.6 days vs 8.1 days, p=0.008). There was no other statistically significant difference between the two operative methods in NTMG patients, including intensive care unit (ICU) stay, ventilator support time, operative time, postoperative status, complete stable remission (CSR) rate, morbidity and mortality. Three prognostic factors associated with better remission rate were hyperthyroidism (p=0.003), age <40 years (p=0.022) and the presence of thymic hyperplasia (p=0.041). Other factors, including gender, disease duration, preoperative MG severity, acetylcholine receptor antibody, perioperative therapy and operative methods (32% vs 36%, p=0.91, 95% confidence interval (CI)=0.27-3.21) were not statistically relevant to better remission rate. CONCLUSIONS VATS thymectomy is more advantageous for NTMG patients because of shorter hospital stay, less tissue injury, better cosmetic result and equivalent CSR rate. NTMG patients aged <40 years with hyperthyroidism and a histologic diagnosis of lymphofollicular hyperplasia have better chances of remission after thymectomy.