Radiologic evaluation of the mediastinum in myasthenia gravis

We reviewed the records of 36 patients with myasthenia gravis who had CT of the anterior mediastinum before thymectomy in an effort to improve preoperative detection of thymoma. At surgery, 10 patients had thymomas, 21 had germinal center follicular hyperplasia, and 5 had histologically normal glands. CT performed on an EMI 5005 was abnormal in 23 of 36 patients; 10 had thymoma, 11 had hyperplasia, 1 had a normal gland, and 1 had a cyst. Tumors were detected by routine chest x-ray in 5 of 10 patients and by linear tomography in 7 of 8. All four patients with calcified masses on CT had thymomas (including the patient with normal linear tomograms). CT alone is too sensitive a screening test; 12 of 25 patients with hyperplasia or normal glands had abnormal scans. However, in combination with chest x-ray and linear tomography, we detected 10 of 10 patients with thymoma with reasonable certainty.