Preoperative pulmonary function is strongly related to myasthenic crisis after thymectomy

Myasthenic crisis can be occasionally a complication after surgery for thymomatous myasthenia gravis (T-MG).

The purpose of this study was to investigate the influence of thymectomy on the subsequent clinical course of T-MG.

Retrospective study.

Only T-MG patients with at least 36 months of follow-up after transsternal thymectomy for thymoma was screened, and those with successfully weaned from a ventilator after surgery were included in the study.

Forty-eight T-MG patients were enrolled during the study period. Myasthenic crisis after thymectomy (MCAT) occurred in 12 (25%) patients with T-MG. Eight (67%) patients with MCAT experienced respiratory failure within the first 1 and 2 years after disease onset. The ratio of measured forced vital capacity (mFVC) to the predicted FVC (pFVC) preoperatively was the only independent factor affecting the occurrence of MCAT (odds ratio, 0.916; 95% confidence interval [CI], 0.867-0.967; P = 0.002). The area under the curve of the receiver operating characteristic for mFVC/pFVC was 0.881 (95% CI 0.754-0.956, P < 0.001), with sensitivity, specificity, and positive and negative predictive values of 58.3%, 97.2%, 87.5%, and 90%, respectively, at a threshold of ≤65% of mFVC/pFVC.

MCAT may occur in patients with T-MG after thymectomy especially within 2 years after disease onset. Preoperative mFVC/pFVC is strongly associated with the occurrence of MCAT postoperatively.