Thymectomy As Primary Therapy In Myasthenia Gravis

In 1982 we presented the results of 47 consecutively presenting myasthenia gravis patients with generalized weakness who were treated by thymectomy according to a standardized protocol (FIG. 1 ).' Plasma exchange without immunosuppression was used to optimize medical status prior to surgery. Anticholinesterase agents were discontinued during plasma exchange in those patients who had received them prior to referral. Patients referred on corticosteroid medications were maintained on these drugs through surgery. Attempts were made to taper and discontinue them postoperatively. Efforts were made to avoid medication whenever possible. Drugs were introduced only when patients experienced deterioration in myasthenic status or had functionally disabling symptoms that persisted following thymectomy. When this population was analyzed after a mean follow-up of 25.5 months, 46 of 47 were improved, 83 percent were free of generalized weakness, and 61 percent were on no medication. Additionally, acetylcholine receptor antibody titers did not predict clinical response to thymectomy, nor did the acetylcholine receptor antibody titer correlate with the clinical status in individual patients. We concluded that (1) thymectomy is an effective therapy for most patients with myasthenia gravis; (2) routine administration of additional medication is not necessary in many patients, and ( 3 ) reduction in the acetylcholine receptor antibody titer is not essential for clinical benefit. These studies suggested the possibility that a "thymic factor" is critical to the development of clinical weakness in myasthenia gravis, and that, while the acetylcholine receptor antibody may play an important role in the pathogenesis of myasthenia gravis, it is the removal of a thymic factor that is responsible for clinical benefits following thymectomy. In the above study, patients were divided into two groups: those who received no previous treatment and those who had received medical therapy prior to referral. To better assess the natural history of thymectomy in the treatment of myasthenia gravis,