Risk factors for the exacerbation of myasthenic symptoms after surgical therapy for myasthenia gravis and thymoma.

Extended thymectomy is employed for patients with myasthenia gravis (MG) and/or thymoma with elevated serum antiacetylcholine receptor antibody (AchR) titers. However, MG symptoms occasionally worsen in postthymectomy patients. We explored the risk factors for exacerbation of MG symptoms after surgical therapy for patients with MG and/or thymoma with an elevated AchR titer. We retrospectively analyzed 90 patients suffering from MG and/or thymoma with an elevated AchR titer who underwent thymectomy in our institute. Patients were classified into Improved, Unchanged and Exacerbated groups by assessing their postoperative myasthenic symptoms, amount of medication and incidence of myasthenic crisis. Risk factors for postoperative exacerbation of myasthenic symptoms were assessed by comparing the Exacerbated with the Improved and Unchanged groups. Of the 90 patients, 29 were classified into the Improved group, 47 into the Unchanged group and 14 into the Exacerbated group. The presence of thymoma and Masaoka stage were significantly different between the Exacerbated and Improved/Unchanged groups. Although preoperative AchR titers did not significantly differ among the groups, the perioperative AchR titers in the Exacerbated group were significantly higher than those in the other groups (P = 0.003). A multiple logistic regression analysis with stepwise forward selection showed that advanced-stage thymoma was a risk factor for postoperative exacerbation of myasthenic symptoms (P = 0.007). Patients with advanced-stage thymoma have a relative risk for exacerbation of myasthenic symptoms after surgical therapy.