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Congenital Spinal and Vertebral Malformations in Cats

Congenital spinal and vertebral malformations are most often genetically inherited (as opposed to adverse conditions during fetal development). Specifically, sacrococcygeal dysgenesis (defective development) is a dominant trait, while thoracic hemivertebra (chest half-vertebra) is a recessive trait.

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 cat undergoes a growth spurt, sometimes not becoming apparent for several months. 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 cat 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.

Symptoms and Types

• 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
• 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
• 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
  • Cat may live normally without symptoms
• Butterfly vertebra
  • 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
  • May remain without symptoms
• Spina bifida
  • Lack of vertebral arches in the spinal column
  • Accompanies sacrococcygeal dysgenesis – a defective formation of the lowest vertebrae in the spine, resulting in a stumped tail
  • 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)
  • Weakness in rear limbs (paraparesis), hopping gait
  • Inherited as an autosomal dominant trait in the Manx breed
• Myelodysplasia
  • Defective development of the bone marrow
• Congenital spinal stenosis (narrowing of the spinal canal - malformation from birth, hereditary)

Causes

• Genetic inheritance
• Possibly, exposure of pregnant queens to:
  • Compounds causing birth defects during fetal development
  • Toxins
  • Nutritional deficiencies
  • Stress

Diagnosis

You will need to give your veterinarian a thorough history of your cat's health and onset of symptoms. A full physical exam will be performed. X-rays of the spinal column (including all vertebrae) can often reveal the exact malformation. If neurological signs (paralysis) are present, a myelography can be used to indicate with precision at which level the spinal cord is compressed. This imaging technique uses a radiopaque substance that is injected into the spine, or into the membranous space that surrounds the spinal cord so that the defects in the spine will be visible on X-ray projections.

Computed tomography (CT) and magnetic resonance imaging (MRI) may also be helpful, and are in some cases much more sensitive than X-rays. However, myelography is generally the diagnostic imaging technique of choice.