Myasthenia, Thymectomy, and Prognostic Predictors
Abstract & Commentary
Source: Nieto IP, et al. Prognostic factors for myasthenia gravis treated by thymectomy: Review of 61 cases. Ann Thorac Surg 1999;67:1568-1571.
To determine prognostic indicators influ-encing outcome following thymectomy for myasthenia gravis (MG), Nieto and colleagues reviewed the clinical records of 61 MG patients, 23 men and 38 women, who, between 1977 and 1994, underwent transsternal (n = 58) or transcervical (n = 3) thymectomy with complete excision of the thymus and neighboring fat tissue. Most were Osserman grade IIa (n = 19) or grade IIb (n = 38), mild or moderate generalized MG, respectively, with two each in grade I (ocular) and III (acute fulminant MG). None was grade IV, severe-late MG. Preoperative treatment comprised anticholinesterase agents (AA) in 25, AA and corticosteroids (C) in 16, AA and C and plasmapheresis (PE) in seven, C in five, AA and PE in six, and PE alone in two, whereas postoperative treatment included AA and/or C as needed. Outcome was measured as complete remission, significant clinical improvement requiring medication, moderate clinical improvement requiring medication, no change, or clinical worsening, and statistical analysis included univariate and multivariate analysis using the Cox stepwise regression model.
Over a follow-up period of eight months to 6 years, 29 patients achieved complete remission, and 28 and four patients, respectively, achieved significant or moderate clinical improvement. Mean age was 30 and 45 years for those who did and did not achieve complete remission, but neither this nor gender or thymic pathology influenced complete remission rate. Stage of disease and length of illness prior to surgery were the only significant prognostic indicators, with complete remission associated with surgery within eight months of diagnosis (P = 0.03), and stage I and III patients more likely to achieve complete remission (P = 0.029). No operative mortality was seen in this group and eight suffered postoperative complications, including wound infection, pneumonia, pneumothorax, pleural effusion, or mediastinitis. Early thymectomy is the key to successful treatment of MG (see Commentary, p. 3). —mr
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