Preoperative preparation of the patient with myasthenia gravis.

All patients who are to undergo a thymectomy should be evaluated thoroughly by a neurologist--ideally one with special training and interest in the diagnosis and management of MG. Confirmatory tests to diagnose MG and other potential diseases should be reviewed. The antibody test seems to be most specific, but there are rare cases of other diseases that are ACh-R antibody positive. In 10% of MG patients, serology is negative, and other tests are necessary to confirm the diagnosis. All patients should undergo a contrast-enhanced high-resolution CT scan with 5- to 8-mm slices because thymoma or thymic carcinoma may be present. Pulmonary function tests, including vital capacity, forced expiratory volume, maximal expiratory force, arterial blood gas, and a flow-volume loop, should be performed. Exercise testing to evaluate for hypoxia and hypotension with exercise and ambulation also may be appropriate. A thorough assessment for cardiac dysfunction, including echocardiography, nuclear medicine studies, or a formal cardiology evaluation, may be beneficial. Because MG is a complex autoimmune disease, preoperative blood tests should include thyroid function testing, antinuclear antibody, and rheumatoid factor in addition to routine preoperative studies. Plasmapheresis or intravenous immunoglobulin should be considered for patients with advanced disease, bulbar symptoms, or poor pulmonary function. Given these guidelines, careful selection of candidates for surgery should optimize the long-term results for patients with MG.