Prognostic Factors of Thymectomy in Patients with Myasthenia gravis: A Cohort of 132 Patients (original) (raw)

Objective: To identify the response to thymectomy and the factors associated with a poor response, a nested case-control study was performed on 132 patients with an established diagnosis of myasthenia gravis who had had a thymectomy between 1987 and 1997 and had been followed up for at least 3 years. Methods: In order to assess the response to thymectomy, the following two points were taken into account: (a) the dose of pyridos-tigmine and other drugs (steroids, azathioprine) that the patient took before and after thymectomy, and (b) the Osserman classification before and after thymectomy. The patients were divided into 4 groups: (1) patients in remission; (2) patients with improvement; (3) patients with no change, and (4) patients who were worse. Results: 91 patients had a good response (69%) and 41 patients had a poor response (31%). The response by groups was as follows: 50 patients were found to be in remission; 41 patients had improved; 34 patients had no changes, and 7 got worse. Being more than 60 years old was associated with a poor prognosis (odds ratio 4.6, CI 1.11–20.32, p 0.01). The patients who had the disease for more than 3 years (odds ratio 2.97, CI 0.79–5.39, p 0.09) had a tendency towards a bad prognosis even though there was no statistical significance, and for those who had it for more than 4 years (odds ratio 2.58, CI 0.89–0.96, p 0.02) the bad prognosis was statistically significant. The patients who had the disease for more than 3 years between diagnosis and thymectomy (odds ratio 2.02, CI 0.69–5.90, p 0.15) and those with it for more than 4 years (odds ratio 2.53, CI 0.83–7.7, p 0.06) had a tendency towards a poor prognosis even though there was no statistical significance. In addition, having Osserman I was associated with a bad prognosis. Referring to the pathological findings, patients with thymoma (odds ratio 3.51, CI 0.43–31.5, p 0.15) and those with thymic atrophy (odds ratio 2.19, CI 0.93–5.16, p 0.04) had a poor prognosis. Finally, the use of steroids before thymectomy (odds ratio 2.26, CI 0.99–5.18, p 0.03) was associated with a worse prognosis. Conclusions: The response to thymec