Prostigmine‐Responsiveness and the Diagnosis of Myasthenia Gravis

Abstract

It is suggested that any syndrome of muscular weakness, not accompanied by alteration of tendon reflexes or sensation, in which strength improves significantly after the administration of adequate amounts of prostigmine or tensilon should be considered to be myasthenia gravis, except when psychoneuroses can be demonstrated to be etiologically important. The presence of inflammatory lesions in skeletal muscle, atrophy of skeletal muscle, or thyrotoxicosis does not automatically change the diagnosis from myasthenia to polymyositis, muscular dystrophy or thyrotoxic myopathy. Although some features may suggest these alternative diagnoses, it may be least confusing to regard any prostigmine-responsive syndrome as myasthenia and to recognize that myasthenia may occur in association with other disorders. The converse of this postulate is not necessarily true, since some patients with a clinical syndrome identical to that described for myasthenia gravis may never respond to prostigmine in diagnostic fashion. Such cases create a problem in understanding those cases of polymositis and weakness associated with hyperthyroidism which do not respond to prostigmine.