Observations on the Nature of Myasthenia Gravis. The Effect of Thymectomy on Neuro-Muscular Transmission 1

Abstract

This communicationi reports a study of the state of neuromuscular transmission, and the effects upon it of prostigmine and acetylcholine injected into the brachial artery, in five patients with severe myasthenia gravis, five months after the total extirpation of the thymus gland. The partial block in neuromuscular transmission and the abnormal reactions to the intra-arterial injection of prostigmine which existed pre-operatively (1, 2) have been altered profoundly. The results of these experiments indicate that in myasthenia gravis the thymus influences greatly the function of the motor nerves and the striated muscles which they innervate. These findings furnish objective evidence of an action of the thymus gland, and an analysis of the results may assist in understanding the normal physiological function of this structure.In addition to changes in the physiological and pharmacological patterns of neuromuscular function which followed thymectomy, there occurred in three of the patients an extraordinary clinical improvement which developed concomitantly with the reversion of neuromuscular function toward normal. METHODSThe methods employed in this study have been described in detail previously (3). Injections of prostigmine and acetylcholine were made into the brachial artery. The ulnar nerve was stimulated through the intact skin above the elbow, by square waves lasting about one millisecond and presented singly, in pairs, or in salvos by the delay circuits of Marshall and Talbot (4). These stimuli, transformer-coupled to the stimulating electrodes, had an amplitude greater than necessary to elicit maximum action potentials from the muscle electrodes placed on the skin over the mn. abductor digiti quiniti. These muscle action potentials were led to the input of a condenser-coupled amplifier and recorded by means of a cathode ray oscillograph.'Aided in part by a grant from the John and Mary R. Markle Foundation.

Effect of Blood Serum From Patients With Myasthenia Gravis on the Synthesis of Acetylcholine in Vitro1

“…The samples from the patient with the least impairment (N), constituting a borderline myasthenic state, presented a defect in synthesis barely below the level of some of the controls (Tables V and VI). 6 While this paper was in press, results similar to those of case S were obtained using serum of 3 additional and comparable patients with myasthenia gravis. Incubated mixtures containing serum collected before and after the administration of 15 mgm.…”

Clinical features, pathogenesis, and treatment of myasthenia gravis: a supplement to the Guidelines of the German Neurological Society

“…Given the role of the thymus in the immunopathogenesis of AchR antibody-associated MG, thymectomy has been considered a treatment option as early as 1942 [ 67 ]. However, randomized controlled trials on the efficacy of thymectomy per se and in comparison to standard immunosuppressive treatment in MG are currently not available [ 18 ].…”

Outcomes after major surgery in patients with myasthenia gravis: A nationwide matched cohort study

“…Mental disorders, limited physical activity, and poor quality of life are significant problems for this socially vulnerable population [ 4 , 5 ]. Thymectomy was considered as an invasive but definite treatment procedure for patients with myasthenia gravis [ 6 – 11 ]. With the increasing incidence of myasthenia gravis in elderly people due to longer life expectancy and improved diagnostic methods, myasthenia gravis patients may be receiving increasing numbers of surgeries other than thymectomy [ 12 ].…”