Outcome after transsternal radical thymectomy for myasthenia gravis: 14-year review at Ratchaburi Hospital.

OBJECTIVE: To determine predictability factors, clinical features and outcome in the patients after transsternal radical thymectomy (TRT) for Myasthenia Gravis (MG).

METHOD: A 14-year retrospective review (1990-2004) and analysis of medical data on 32 patients with MG who underwent TRT. Two patients were lost to follow-up. Preoperative medication included anticholinesterase drugs and steroids. Plasmaphereses were used in 2 cases before operation. The modified Osserman clinical classification (Table 1) was used to define disease severity. The status of the patients was evaluated as follows: A (remission), B (improvement), C (no change), D (deterioration), E (death due to myasthenia gravis). Using univariate analysis, sex, age, onset, Osserman class and pathology correlated with outcome and statistical significance is defined as P < 0.05.

RESULTS: Among the 30 patients in the present study with MG who underwent TRT women comprised 70% (21 of 30 patients), and mean age was 42.87 +/- 12.16 year (19-65 years). The preoperative duration of the disease ranged from 0.5 to 120 months (mean = 25.72 +/- 30.68 months). Clinical statuses of patients as assessed on initial evaluation were 13 patients (43.3%) were in class IIA, 6 (20%) in class IIB, and 11 (36.7%) in class III. (Table 2) The histology of thymus glands consisted of hyperplasia in 22 patients, normal in 2, atrophic thymus in 3, thymomas in 3, (2 were malignant thymomas). Hospital mortality was 0, but 9-month mortality was 3.33% (1 of 30 patients). The mean follow-up period was 41.80 +/- 53.89 months. Complete remission (A) was achieved in 40% of patients (12 of 30), and marked improvement (B) of MG in 40% (12 of 30), for a total benefit rate of 80%. 6.7% (2 of 30) were unchanged (C), 10% (3 of 30) were worse (D) and 3.3% died because of MG (E). Using univariate analysis on sex, clinical status by Osseman classification, and histopathology correlated significantly with outcome (P < 0. 05); 95.2% of women (20 of 21) benefited from the procedure, versus 44.4% of men (4 of 9). 100% (19 of 19) of patients in class IIA and IIB benefited from the procedure, versus 45.5% (4 of 9) of patients in class III. All patients with thymoma presented a less favorable outcome (deteriorated in 2, and died in 1) versus 11.1% (3 of 24) of patients without thymomas were deteriorated.

CONCLUSION: The remission and improvement in 80% of patients suggested that adequate thymic tissue were removed with radical thymectomy. Female, absence of thymoma, thymic hyperplasia, patients in class IIA, and IIB (non-respiratory involvement) are favorable predictability prognostic factors.