THYMUS IN MYASTHENIA-GRAVIS - COMPARISON OF CT AND PATHOLOGICAL FINDINGS AND CLINICAL OUTCOME AFTER THYMECTOMY

PURPOSE: To correlate computed tomographic (CT) appearance of the thym us with results from histologic examination of thymic tissue and clini cal outcome in patients with generalized myasthenia gravis who underwe nt thymectomy. MATERIALS AND METHODS: Forty-five patients with myasthe nia gravis underwent CT of the thorax and thymectomy. Findings at clin ical follow-up were available in all patients. RESULTS: Twenty-six pat ients had normal CT findings, seven had a diffusely enlarged thymus, a nd 12 had a focal mass. The results of histologic examination showed t hat 16 of 26 patients with normal CT findings had normal thymic tissue and 10 had lymphoid follicular hyperplasia; all seven patients with a n enlarged thymus had lymphoid hyperplasia. Five of 12 patients with a focal mass at CT had lymphoid hyperplasia, and seven had thymoma. Cli nical improvement following thymectomy was observed in 27 (93%) of 29 patients with lymphoid hyperplasia or thymoma and 11 (69%) of 16 patie nts with normal histologic examination (P < .03, x(2) test). CONCLUSIO N: The presence of an enlarged thymus or a focal mass in patients with myasthenia gravis indicates lymphoid hyperplasia or thymoma. However, CT is of limited value in distinguishing lymphoid follicular hyperpla sia from a normal thymus or thymoma and in predicting clinical outcome .