The relief of myotonia by the use of a potassium-binding resin.

The phenomenon of myotonia comprises a lingering relaxation of muscle after contraction, and a slow tonic response to stimuli of an electrical or mechanical nature. The condition may be ameliorated or even extinguished by repeated effort. Although well known and the commonest form of hereditary muscular disorder seen in young adults, it is, nevertheless, a rare condition. Three distinct forms of the disturbance are recognized: (a) Myotonia congenita, where the disability exists in a simple form; (b) myotonia atrophica, in which disease the defect is associated with muscle wasting of typical distribution; and (c) paramyotonia congenita, a disorder in which myotonia and weakness are especially prominent on cooling and may be associated with muscle atrophy. It is doubtful whether the three conditions are in fact entities and there is much overlapping between them. The literature of these conditions has frequently been reviewed, most recently by de Jong (1956) and can probably best be summarized by saying that so far no unanimity has been arrived at either in describing the physiological or pathological factors underlying the condition or in arriving at a uniformly satisfactory method of treatment for the disability. Liversedge and Newman (1956) reported on the satisfactory effect of cortisone in myotonia and concluded that it was probably due to a modification of the susceptibility of the muscle cell membrane to potassium ions. They were in doubt as to whether the actual elimination of potassium from the body was a factor. It was felt that this point could be further settled by a procedure specifically directed towards removing potassium, the more so since long-continued administration of cortisone is frequently accompanied by undesirable side-effects which may be serious (Allanby, 1957). It was decided to investigate the effect of a potassiumbinding ion-exchange resin for this purpose. This method of treatment had previously been used by Gruttner and Mertens (1953) in a case of myotonia congenita with satisfactory results but has not been reported before in Great Britain and there is no record of the results of treatment of a case of myotonia atrophica. Incidental investigation was made into the biochemical changes caused by exhibition of quinine and procaine amide as control substances.