[Electromyography using needle electrodes to analyze the structure and functional state of motor units in neuromuscular diseases].

Results of electromyographic examinations of over 1,000 patients with various forms of acute and chronic neuromuscular diseases and progressing myodystrophies are analyzed. The examinations were carried out with the use of needle electrodes. On comparing the electromyographic findings with the clinical ones and with the results of examining muscle biopsy specimens 5 electromyographic stages of motor unit changes occurring in the course of the development and compensation of the pathological process were differentiated. Stage I was characterized by a shortening of the duration of the activity potentials in some motor units, with the average duration of the motor unit activity potentials remaining unchanged. In Stage II the average duration of the motor unit activity potentials, due to a considerable shortening of most of them, diminishes by more than 20%. In Stage III, along with the short-duration potentials there appear much longer potentials with a duration exceeding the normal ones. Characteristic for Stages IV and V was prevalence of long motor unit activity potentials the average duration of which was by 20 to 40% greater than that of the normal ones. Data characterizing the degree of the spontaneous activity of muscular fibres (potentials of fibrillations and positive acute waves), as well as the spontaneous activity of the motor units (fasciculations) in various stages of their impairment are presented. The importance of evaluating the motor unit activity potentials and the spontaneous activity of the muscular fibres for diagnosing and studying the mechanisms of the development of neuromuscular diseases is discussed.