Prognostic factors and outcome of thymectomy in 80 cases of myasthenia gravis

Objectives: To analyze the results of thymectomy in our series of patients with myasthenia gravis (MG) and to study the influence of the most common prognostic factors. Material and methods: Eighty MG patients over a period of 23 years underwent thymectomy consecutively in our hospital. Preoperative assessment included clinical evaluation of muscle weakness, edrophonium testing, electromyography, lung function testing, chest X-rays and CAT scans. Symptoms were assessed by the Osserman scale. The surgical approach was amplified transsternal thymectomy. The prognostic factors studied were sex, age, clinical stage, duration of disease before surgery and histology of the thymus. Clinical outcome was assessed using Millichap and Dodge's criteria. Follow-up was by the chest surgery and neurology departments. Results: Complete remission was observed in 29 cases (36.2%) and significant improvement in 42 (52.5%). Complications developed in 9 patients (11.2%). Most patients were women (53/27) and outcomes for men and women were not statistically different. Mean age was 36 years (range 11-79), with no significant difference in outcome for patients who were older or younger than 60 years of age. Nor were differences evident related to presurgical clinical stage or levels of severity (I + IIa/IIb + III). Differences in outcome were highly significantly related to duration of disease (<24/>24 months) (p=0.0022), such that outcome was more satisfactory when the pre-surgical course of disease was shorter, provided that no thymoma was present. Conclusions: Amplified transsternal thymectomy was safe and effective for those patients with MG. When disease had been present for less than two years, the prognosis was better.