Computed tomography of the thymus in myasthenia gravis

Comparison of preoperative CT diagnosis and histopathological diagnosis for the thymus were studied in 39 patients with myasthenia gravis. The patients consisted of 10 patients with thymoma and 29 without thymoma confirmed at the operation. CT diagnosis was 11 thymomas, 18 thymic hyperplasias and 10 normal thymuses. Eleven thymomas revealed histopathologically 9 thymomas, one follicular lymphoid hyperplasia (FLH) and one involved thymus. Out of 18 thymic hyperplasias 15 cases were FLH and 3 involved thymus. There were 5 involved thymuses, 4 FLHs and one thymoma in the 10 normal thymuses on CT. The finding of 'reticular pattern', many small nodules scattered reticularly in the thymus, in computed tomography could be regarded as a sign suggesting FLH of the thymus. The accuracy of this finding of CT was 83% for FLH. The finding of thymoma on CT revealed 82% of the accuracy. Therefore, CT was very useful in the diagnosis of the localization of the thymoma but not for the diagnosis of FLH of the thymus. Nevertheless the finding of 'reticular pattern' on CT was helpful in the diagnosis of FLH. (author)