Myotonia.

The clinical and electrophysiologic features of myotonia can be seen in a number of human diseases as well as in several well-studied animal models. In some cases the underlying pathophysiologic mechanism has been defined, but different and as yet undetermined membrane abnormalities are present in others. In spite of the differing mechanisms that can produce the repetitive electrical activity characteristic of myotonia, the involvement of the voltage-dependent sodium channel as the final common pathway in the expression of this activity provides a target for therapeutic intervention. A number of drugs that modify sodium channel activation kinetics can be used to effectively control the symptoms of myotonia.