Myotonia
Myotonia occurs as a congenital problem in many breeds of dogs. The prolonged muscle contraction is thought to be due to an abnormal muscle cell membrane that supports persistent depolarization. Animals with myotonia have sustained muscle contraction, which is initiated voluntarily or with stimulation, and sustained involuntarily. Myotonia most often occurs as a congenital problem, however, the disease can be acquired with some toxicities (some herbicides) and secondary to hyperadrenocorticism.
Age of Onset:
Congenital: First few weeks of life
Acquired: any age
-Hyperadrenocorticism-associated - usually older animals
Congenital: First few weeks of life
Acquired: any age
-Hyperadrenocorticism-associated - usually older animals
Sex Predisposition: Any sex of animal can be affected
Clinical Course:
Muscle “stiffness” manifested by limb extension and short step distances is most prominent after periods of rest and will often reduce in severity as the dog repeatedly uses their muscles during movement.
Muscle “stiffness” manifested by limb extension and short step distances is most prominent after periods of rest and will often reduce in severity as the dog repeatedly uses their muscles during movement.
Clinical Signs:
Posture and Appearance
Muscle dimpling may occur with direct muscle percussion
Extended limbs with movement
Movement
Short-”stilted” gait
Short step or interstep distances
Bunny-hopping gait
Stiffness and extensor rigidity of the limbs
Muscle Atrophy
Appendicular muscle hypertrophy
Glossal hypertrophy
Other
Polyphagia/Polydipsia/Polyuria (Hyperadrenocorticism associated)
Posture and Appearance
Muscle dimpling may occur with direct muscle percussion
Extended limbs with movement
Movement
Short-”stilted” gait
Short step or interstep distances
Bunny-hopping gait
Stiffness and extensor rigidity of the limbs
Muscle Atrophy
Appendicular muscle hypertrophy
Glossal hypertrophy
Other
Polyphagia/Polydipsia/Polyuria (Hyperadrenocorticism associated)
Diffuse neuromuscular
Autosomal recessive mutation in chloride channel (ClC-1 gene)
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