Put simply, without Purkinje cells, an animal loses its sense of space and distance, making balance and coordination difficult.

People with damage to the cerebellum can experience symptoms like unsteady gait, poor muscle control, and trouble speaking or swallowing.

In addition to dogs and horses, there also have been cases of cerebellar abiotrophy in Siamese and Domestic shorthair cats; in Angus, Polled Hereford, Charolais and Holstein Friesian cattle; Merino and Wiltshire sheep; and Yorkshire pigs.

Symptoms of cerebellar abiotrophy include ataxia or lack of balance, an awkward wide-legged stance, a head tremor (intention tremor) (in dogs, body tremors also occur), hyperreactivity, lack of menace reflex, stiff or high-stepping gait, coarse or jerky head bob when in motion (or, in very young animals, when attempting to nurse), apparent lack of awareness of where the feet are (sometimes standing or trying to walk with a foot knuckled over), poor depth perception, and a general inability to determine space and distance.

Verifying the diagnosis in a laboratory setting is possible only by examining the brain post-mortem to determine if there has been a loss of Purkinje cells.

Horses may experience difficulty stepping up and over objects, run into fences, fall easily, and even if allowed to mature to full growth, are generally considered unsafe to ride.

There also is some evidence that affected animals partially compensate for the condition by cognitively learning alternative methods for moving or to determine distance, and thus appear to improve because they become less accident-prone.

Breeds DNA tested that reveal some carrier lines, but to date no affected animals, include the Welsh pony and the Trakehner.

Though the symptoms are quite distinguishable from other neurological conditions, it has been confused with Wobbler's syndrome, equine protozoal myeloencephalitis, and injury-related problems such as a concussion.

[12] Most breeds prone to the condition, such as the Kerry Blue Terrier, Border Collie, Australian Kelpie, and Labrador Retriever, begin showing symptoms between six and sixteen weeks of age.

[12] In a very few breeds, such as the American Staffordshire Terrier, Old English Sheepdog, Brittany Spaniel, and Gordon Setter, symptoms do not appear until adulthood or even middle age.