The electrical characteristics of myotonia in skeletal muscle appear remarkably similar in a variety of natural disorders and animal models. Recent experimental work has made it clear, however, that the pathophysiologic mechanisms underlying these myotonic discharges can be quite different. A mechanistic classification that subdivides these disorders into groups sharing common pathophysiologic features may provide additional insight into their pathogenesis. This article will review our knowledge of myotonic mechanisms and propose one approach to such a classification.
