Congenital vertebral malformations are commonly found in neurologically normal dogs. Do not presume a causal relationship between neurological signs and a vertebral malformation on the basis of non-contrast radiographs. Malformation of the vertebral body rarely causes a problem.
A hemivertebra has a wedge-shaped vertebral body and most commonly occurs in the thoracic or coccygeal vertebrae of screw-tailed breeds such as pugs and bulldogs. Adjacent vertebrae alter their shape to conform, resulting in scoliosis or kyphosis. Thoracic hemivertebrae may lack a rib.
Butterfly vertebrae have a cleft in the vertebral body with or without lateral spread of the two halves, and funnel-shaped endplates. They are not clinically significant and are most common in the screw-tailed breeds.
Spina bifida is a developmental anomaly with a midline cleft in the dorsal vertebral arch through which spinal cord and meninges may penetrate.
Block vertebrae are composed of two or more vertebrae fused into one. Bone density is normal. The overall size may be shorter.
A transitional vertebra is one occurring at the junction of two regions that takes on the characteristics of the arch and articular facets of the adjacent division.
The dog had always been clumsy since she was acquired as an 8-week old puppy. She has struggled to rise from sitting and has abducted all limbs when walking on tiled flooring all her life. No hip disease had been found to account for this. Three days prior to presentation the dog had slipped on a wet tiled floor and fallen, collapsing to the ground. She was unable to rise, but could crawl. Two days later she was able to stand and walk unaided but had hindlimb ataxia. The dog did not appear to be in pain.
The dog was slow to rise from sitting but could do so unaided. She showed hindlimb ataxia with the right hindlimb circumducting at each step. The forelimbs had a shortened stride length. Hopping was normal in the forelimbs but slow in the hind, especially the right hindlimb. Proprioception was normal in the forelimbs but slow in the hindlimbs. When standing, the dog shifted most of its weight to the forelimbs. Muscle tone was increased in both hindlimbs. Spinal reflexes were increased in the hind and normal in the forelimbs.
The lesion was localized to the T3–L3 spinal cord or the cervical spinal cord. Large and giant breed dogs with cervical cord lesions can present with hindlimb UMN signs.