This is a hereditary movement disorder.

Affected pups develop normally until about 4 months of age.

Then their head starts to shake when they focus on something, and rather than becoming stronger and more coordinated, they develop exaggerated, goose-stepping movements (cerebellar ataxia).

Dogs can function with cerebellar ataxia, but CMSD progresses to a more severe movement disorder by 12-18 months of age.

Affected dogs have difficulty even starting a movement and fall frequently.

They become incapacitated by 2 years of age.

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