Hemivertebrae

In hemivertebrae, the right and left halves of the vertebra do not fuse as they should, and the two halves grow unequally. This most often happens in the chest area of the vertebrae, where it can cause curvature of the spine either side to side or up and down. In some cases, it causes a kink in the spine, compressing the spinal cord. In these cases, surgery may be needed to prevent partial paralysis. Screening radiographs can be done even in puppies.

Breeds at Risk

Hemivertebrae can be found in any breed but occur most often in short-skulled (brachycephalic) dog breeds including Pugs, Boston terriers and Bulldogs. Most of the time, they cause no obvious abnormality, although they can be associated with spinal deformity, which includes marked curvatures of the skeletal bones of the back, humpback, and abnormal curvature of the spine (scoliosis). When disease develops, it is because of the narrowing of the spinal canal related to severe deformity and underdevelopment of the spinal cord.

The condition is present at birth and usually becomes apparent at 6 to 12 months of age, when the misshapen vertebrae become interfering with the nerves controlling the hindquarters, causing the puppy to trip frequently or even become paralyzed. Some dogs respond well to acupuncture, but others are permanently paralyzed.

References:
1. Veterinary Diagnostic Imaging. Charles S. Farrow
2. The Everything Pug Book. Kim Campbell Thornton
3. French Bulldogs. D. Caroline Coile Ph.D., D. Caroline Coile, Michele Earle-Bridges