Muscle hypertonicity in the cavalier King Charles spaniel--myopathic features

Canine Paroxysmal Movement Disorders

“…14,15 It is also known as sudden collapse, muscle hypertonicity, and hyperekplexia, although the latter term is misleading because "hyperekplexia" Abbreviations: GLUT1, glucose transporter type 1 gene (also known as SLC2A1); KCNMA1, calciumactivated potassium channel, subfamily M, alpha member 1; MR-1, myofibrillogenesis regulator 1 (the function of this gene is poorly understood); PED, paroxysmal exertion-induced dyskinesia; PKD, paroxysmal kinesigenic dyskinesia; PNKD, paroxysmal nonkinesigenic dyskinesia; PRRT2, proline-rich transmembrane protein 2 gene (defects in this transmembrane protein are thought to destabilize synapses and alter neuronal excitability but the pathophysiologic basis requires more investigation).…”

“…There are no significant clinical or neurologic abnormalities and no spontaneous discharges on electromyography in between episodes. 15 The benzodiazepine, clonazepam (0.5 mg/kg every 8 hours), has been used to treat episodic falling effectively 17 and acetazolamide is also reported to be beneficial. An autosomal-recessive mode of inheritance has been demonstrated.…”

“…18 On postmortem examination, a variety of changes have been described in skeletal muscle, such as enlargement and proliferation of the sarcoplasmic reticulum, but these are likely to be secondary to excessive muscle contractions. 14,15,19 Recently, this dramatic condition has been linked to a deletion in the gene BCAN 18,19 that encodes a protein called brevican. This protein is a component of the extracellular matrix proteoglycan complex and is found at high levels in the central nervous system as part of the perineuronal network.…”

“…Typically, an episode is characterized by lowering of the head, arching of the lumbar spine, stiffness of the limbs that creates a 'deer-stalking' posture, and falling over. 8,15 The duration of episodes varies among cases ranging from a few seconds to several minutes 8,15 and they are self-limiting or can be limited by interaction with the owner. 8 There is no loss of consciousness during the period of collapse.…”

Paroxysmal Dyskinesia Suspected as Canine Epileptoid Cramping Syndrome in a Young Yorkshire Terrier Dog

“…This hypertonicity syndrome was first observed in young Scottish terriers and was called “Scottie cramps” [2]. Previous studies showed similar clinical signs in Cavalier King Charles spaniels, springer spaniels and wheateon terriers [7, 13, 16]. The term “canine epileptoid cramping syndrome” (CECS) was first used for Border terriers in 2012 and is characterized by a paroxysmal cramping or hypertonicity syndrome [1, 3].…”