Cerebellar Abiotrophy (CA) Symptoms

(also known as Canine Ataxia)

By Dr. H. Steven Steinberg, DVM, DACVIM (Neurology)

In 1994 adult Old English Sheepdogs were presented to me with a progressive abnormality in their gait. It became evident that this problem was widespread and has been recognized in various parts of the country. The underlying cause of this disease, the genetic basis of this disease as well as defining an appropriate approach to decreasing the incidence of this disease, commonly called Cerebellar Degeneration or Cerebellar Abiotrophy (CA), is ongoing at a number of centers.

Other Cerebellar degeneration conditions have been described over the years including one in Gordon Setters described by me in 1981. The Cerebellum is part of the brain that is critical for controlling smooth, efficient, and effective movement.

This short description will define a few of the hallmarks of this condition but it must be noted at the outset, that a veterinarian and in many cases a veterinary neurologist is necessary to diagnose this condition. Many of the gait abnormalities seen with this condition are subtle and even in its most advanced form CA mimics other orthopedic and/or neuromuscular conditions. This condition seems less severe and progresses more slowly than most other Cerebellar Degenerations reported. Older affected dogs that get around reasonably well have been seen. Dogs do not die from this condition.

The most obvious abnormality in these dogs is a basewide hindlimb stance and gait. Typically when dogs walk they should move their paws towards midline. This is best appreciated when the dogs are walking away from the viewer. CA dogs tend to stand with their hindlimbs far apart and have mild to moderate circumduction. Circumduction is where the paw is carried outside of a line dropped vertically to the ground from the hip joint. The paw also strikes the ground far from the midline and usually outside of a line dropped vertically from the hip joint.

A second noteworthy gait abnormality is known as hypermetria. Evidence of hypermetria is seen in dogs with CA when they lift their legs much higher than is normal or appropriate. This is best appreciated in the forelegs. In many breeds with broad chests or white chests (like Boxers) this prancing gait is considered desirable by some in the show ring. It is difficult sometimes to appreciate this abnormality but when watching a severely affected dog from the side their carpus (wrist joint) may be raised as high as their shoulder joint before placing the paw on the ground.

In the later stages of the disease, the dogs are extremely wobbly (ataxic) and their gait problem becomes much easier to appreciate.

Although the condition has been presented in dogs who are young adults, there may be subtle changes in puppies.

Reprinted with permission from Old English Times, December 1998. , pp. 35.