[Familial myotonic syndrome with hyposthenia corrected with exercise (author's transl)].

In some cases of myotonic syndromes a paresis after rest has been described corrected by exercise. This syndrome is reported in two brothers. In myotonic patients repetitive stimulation of a nerve causes a transitory decrease of the muscle action potential. Probably the paresis corrected by exercise only represents the clinical evidence of the electrophysiological phenomenon mentioned above. This seems to be a common occurrence and therefore does not represent a new nosologic entity.