The role of radiation therapy in myasthenia gravis

Myasthenia gravis is a serious and debilitating disease associated with conduction defects occurring at the myoneural junction. About 15 per cent of the patients have associated tumors of the thymus and 80 per cent of the remaining patients show abnormalities of the thymus. Although a definite relationship between cause and effect has not been proved, thymectomy or radiotherapy of the thymus does seem to influence the disease. Seven cases of myasthenia gravis in which radiation therapy was used at the University of California Medical Center are reported and compared with those described in the literature. It is concluded that patients whose disease is progressing and not well managed medically, and who have no evidence of thymoma, should be treated by irradiation-whether pre-operatively or as definitive treatment, depending on the result of irradiation. Those patients with evidence of thymoma should be irradiated before surgical procedure. Small tumors, or patients in whom surgical risk is increased, may be managed by radiation therapy alone.