Myotonia, the persistent contraction of a muscle after voluntary, mechanical, electrical or, in some instances, reflex stimulation, is the chief symptom of myotonia congenita, or Thomsen's disease. Myotonia is also a prominent symptom of certain other muscular dystrophies, particularly dystrophia myotonica (myotonia atrophica).
Erb, in 1886, described the essential clinical and pathologic manifestations of myotonia congenita as well as the characteristic reactions of myotonic muscles to electrical stimulation. Curschmann1 was one of the first to take into full account the extramuscular symptoms which may be associated with myotonia and atrophy in dystrophia myotonica. Since summaries of the literature and reviews of some of the more typical cases reported may be found in publications by Jacoby,2 Johnson and Marshall,3 Rosett,4 Adie and Greenfield,5 Jelliffe and Ziegler6 and others, no attempt will be made here to repeat the detailed descriptions of these related syndromes. Suffice it
LINDSLEY DB, CURNEN EC. AN ELECTROMYOGRAPHIC STUDY OF MYOTONIA. Arch NeurPsych. 1936;35(2):253-269. doi:10.1001/archneurpsyc.1936.02260020047004