[Electromyographic features of 3 forms of myotonia]

On the basis of a great body of examination data the electromyographic peculiarities of three forms of myotonia are analyzed. As a result, the authors come to a conclusion that in the third form of myotonia the function of muscular fibres is grossly impaired, this impairment following the pattern of their being put out of activity. This failure appears invariably during the muscle activity and leads, in the end to the clinically observed transient, and in more advanced cases, moderately permanent weakness of the muscles and their hypotrophy. In addition, data on synaptic apparatus involvement were also obtained. The time course of the development of those disorders, as regards the neuromuscular conduction and the distal parts of the muscular fibres is followed. In atrophic myotonia, certain peculiarities of the electrophysiological characteristics of the neuromuscular periphery were noted. In particular, a marked phase of secondary refractoriness was revealed. Thomsen's myotonia was found to differ substantially in the electrophysiological characteristics from the above two forms of the myotonia. Although in a number of cases it is difficult to class a particular case with one or another form of myotonia (this can be explained by an exceedingly great diversity of the biochemical peculiarities inherited by each individual) the differentiation of the above three forms of myotonia is justified from the viewpoint of both exploring the pathogenesis of the disease forms, and choosing the treatment method the most effective in this particular case. Of importance in solving these problems may be diversified electrophysiological examinations of the motor apparatus, and comparisons of their results with those of clinical examinations.