Thymectomy for myasthenia gravis: predictive factors and long term evolution. A retrospective study on 46 patients.

Forty-six patients with myasthenia gravis (MG) underwent transternal thymectomy between 1975 and 1991 and were observed over a long term follow up period (mean 6 years). Surgery was well tolerated and was followed in 32.6% of patients by remission of symptomatology. The severity of symptoms according to the Osserman scale was significantly reduced: slight forms of myasthenia increased soon after thymectomy more frequently than moderate and severe forms. Response to thymectomy at 3 months, according to the Hankins scale, was found to be positive (remission or amelioration of symptoms) in 31/41 patients, and worse in patients with thymoma. Probability of clinical remission and death were both significantly correlated with clinical response at three months after thymectomy. No other preoperatory clinical factor (onset age, sex, initial severity of MG, interval from symptom onset to thymectomy) was found to predict the response to treatment. Preoperatory mediastinic CT had a good reliability (> 85%) in diagnosing thymona, but was rarely able to distinguish between thymic hyperplasia and atrophy.