Spinal and Vertebral Birth Defects in Dogs

Congenital vertebral anomalies are a collection of malformations of the spine in animals. Congenital vertebral malformations if severe enough can result in malalignment and/or instability of the spine resulting in compression on the spinal cord. A congenital defect or abnormality is a trait that the puppy is born with, i.e. a condition that exists at birth. A lot of congenital defects are hereditary and caused by genetic factors, but they can also be the result of something that happened while the puppy was still in its mother’s womb. 

Spinal malformations are usually evident at birth or in the first few weeks of life. On the other hand, vertebral malformations can be latent until the dog undergoes a growth spurt around five to nine months of age. Visible signs of a distorted spinal column are lordosis (curvature of the spine at the lower back) and kyphosis (a posterior curvature of the spine).

Scoliosis (a lateral curvature of the spine) is also an easily visible form of vertebral malformation. If the malformations lead to secondary spinal cord compression and trauma, the affected dog will display ataxia and paresis. Medicine often does not resolve neurological manifestations of spinal and vertebral malformations. If the condition is severe and untreatable, euthanasia should be considered.

Common symptoms and predisposed breeds are:

Malformation of the occipital bones – atlas and axis (the first and second cervical vertebrae at the base of the skull):

Causes compression of the upper spinal cord, which can lead to paralysis, sudden death

More common in small-breed dogs

Hemivertebra (half a vertebra)

Kyphosis, scoliosis, lordosis

Wedge shaped vertebrae, causes angle in the spine

Most likely to affect the neurological system

Rear limb weakness (paraparesis), paralysis

May remain without symptoms

Affects breeds with a short skull, and “screw-tailed” breeds (may be desired in some breeds)

Pugs, Boston terriers, French and English bulldogs

Transitional vertebra

Has characteristics of two types of vertebrae

May result in cord compression, disc changes

Block vertebra

Fused vertebrae due to improper segmentation of vertebrae

Animal may live normally without symptoms

Butterfly vertebra (vertebra with a cleft through the body and a funnel shape at the ends):

Vertebra with a cleft through the body and a funnel shape at the ends (giving appearance of butterfly on X-ray examination)

Causes instability of the vertebral canal, and rarely, compression of the spinal cord with paralysis

Sacrococcygeal dysgenesis

Defective formation of lowest vertebrae in the spine

Associated with spina bifida (lack of vertebral arches in the spinal column)

Spina bifida

Variable spinal dysplasia (abnormal development); dysraphism (defective spinal fusion); syringomyelia (cyst in the spinal cord); hydromyelia (enlarged central canal in the spinal cord where excess cerebrospinal fluid builds up); and myelodysplasia (defective development of the bone marrow)

Dog may not show symptoms

Bulldogs, pugs, Boston terriers


Defective development of the bone marrow


Congenital spinal stenosis (narrowing of the spinal canal – malformation from birth, hereditary)

Chondrodystrophic (dwarf) breeds

Basset hound, beagle, dachshunds, lhasa apso, shih tzu, Pekingese

Doberman pinschers are also genetically disposed

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