[Electromyographic and morphological analysis of the changes in the motor units in myasthenia, combined myasthenia with thymoma and polymyositis and terminal polyneuropathy with myasthenic syndrome].

Changes of the activity potentials of motor units and muscular fibres registered with the aid of needle electrodes are compared with the results of morphological examinations of biopsy specimens of 1,096 muscles taken from 137 patients with myasthenia, combinations of myasthenia with thymoma and polymyositis, as well as from patients with terminal polyneuropathy with the myasthenic syndrome. It has been shown that characteristic of myasthenia are differentiated changes of the motor unit activity potentials: in half of the muscles examined the parameters of those potentials were found to be normal, no polyphasic or protracted potentials were observed. In the patient with combinations of myasthenia with thymoma, polymyositis, and in terminal polyneuropathy with the myasthenic syndrome pronounced changes of all the activity potentials of the motor units were observed in the form of both a sharp shortening and a prolongation of their duration; a great number of polyphasic potentials was registered and spontaneous activity of various degree was observed. Morphological examinations of 55 biopsy specimens of the muscles of the same patients revealed a correlation between the degree of the dystrophic and atrophic changes of the muscular fibres and depth of the affection as determined on the basis of electromyographic findings.