Comparison of Ct and Pathologic Findings & Clinical Outcome after Thymectomy with or without Plasmapheresis in Patients with Myasthenia Gravis

Objective: To compare computed tomographic (CT) appearance of the thymus with results from histologic examination of thymic tissue and clinical outcome in patients with myasthenia gravis who underwent thymectomy with or without plasmapheresis. Method and Materials: This study comprised of 47 patients, who were operated on in the period from January 2002 to December 2009 for myasthenia gravis. Computed tomography was done in all cases .Of these 47 patients, preoperative plasmapheresis was performed in 20 patients (group B) and the remaining 27 patients (group A) had no preoperative plasmapheresis based on non availability of plasmapheresis kit. Outcome in the form of requirement of ventilation, symptomatic improvement, hospital stay and requirement of drugs were assessed at the end of one year and compared between the two groups. Specimens sent for histopathology were analyzed. Follow up was done in all cases. Results: Eighteen out of twenty seven patients (66%) in group A required ventilatory support in the immediate postoperative period, whereas four out of twenty patients (20%) in group B required it. Significant and sustained symptomatic improvement was noted in group B as compared with group A (P-0.01). Twenty-eight patients had normal CT findings, seven had a diffusely enlarged thymus, and 12 had a focal mass. The results of histologic examination showed that 16 of 28 patients with normal CT findings had normal thymic tissue and 12 had lymphoid follicular hyperplasia; all seven patients with an enlarged thymus had lymphoid hyperplasia. Five of 12 patients with a focal mass at CT had lymphoid hyperplasia, and seven had thymoma. Conclusion: CT is of limited value in distinguishing lymphoid follicular hyperplasia from a normal thymus or thymoma and in predicting clinical outcome. Preoperative plasmapheresis in the patients of myasthenia gravis is beneficial and can cause a significant difference in the postoperative outcome.