Affected dogs usually present with episodes of collapse from a young age, usually 3 - 7 months. The symptoms are often elicited by exercise, excitement or stress-induced and is characterised by muscular hypertonicity and abnormal posturing, with affected dogs appearing to demonstrate a temporary inability to relax the affected limb and trunk muscles.
The episodes are usually brief (less than five minutes) and self-limiting, but the clinical signs between cases are variable, with the length of an episode ranging from a few seconds to several minutes. Episodes start with an increase in muscle tone, with bunny-hopping movements and/or presence of a “deer stalker” gait.
The back may become arched and the head held close to the ground leading to collapse, either to the side or forwards. Legs may be held out in a rigid, extended fashion, although in some cases the dog may return to the feet within seconds of a collapse. In some of the most severe cases, forelegs or hind legs become protracted until they are positioned over the top of the dog's head. Dogs appear to remain fully conscious during an episode.
There is no known treatment for this condition and the response to treatment is poor, although some limited benefit has been described using anticonvulsant medications.
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- Wright JA et al (1986) Muscle hypertonicity in the cavalier King Charles spaniel–myopathic features. Vet Rec 118:511–512
- Weber YG et al (2008) GLUT1 mutations are a cause of paroxysmal exertion-induced dyskinesias and induce hemolytic anemia by a cation leak. J Clin Invest 118:2157–2168