Paradoxical pseudomyotonia in English Springer and Cocker Spaniels

Background Paramyotonia congenita and Brody disease are well-described conditions in humans, characterized by exercise-induced myotonic-like muscle stiffness. A syndrome similar to Brody disease has been reported in cattle. Reports of a similar syndrome in dogs are scarce. Objectives To define and describe the clinical, diagnostic, and genetic features and disease course of paradoxical pseudomyotonia in Spaniel dogs. Animals Seven client-owned dogs (4 English Springer Spaniels and 3 English Cocker Spaniels) with clinically confirmed episodes of exercise-induced generalized myotonic-like muscle stiffness. Methods Sequential case study. Results All dogs were <24 months of age at onset. The episodes of myotonic-like generalized muscle stiffness always occurred with exercise, and spontaneously resolved with rest in