Felis ISSN 2398-2950

Spine: congenital vertebral malformations

Synonym(s): Sacrocaudal dysgenesis; Hemivertebrae; Spinal stenosis; Atlanto-axial instability; Centrum hypoplasia

Contributor(s): Laurent Garosi, Simon Platt


  • Cause: developmental anomaly.
  • Signs: can be asymptomatic and often incidental findings, cause visible or palpable gross spinal deformities if cord compression or instability   →   myelopathy, radiculopathy or pain
  • Diagnosis: radiography.
  • Treatment: surgical decompression and/or stabilization if appropriate.
  • Prognosis: signs may deteriorate as animal grows.



  • Unknown in most cases.
  • Genetic predisposition or mutation identified in some cases.
  • Many potential causes postulated (toxin exposure, storage disease Storage disease such as feline mucolipidosis II, teratogenous drugs, metabolic diseases...)


  • Vertebral column anomalies originating in the embryonic period are caused by defects in formation, and may be associated with neural tube defects. They include:
    • Butterfly vertebrae result from incomplete intradiskal migration of notochordal material resulting in bifid centrum formation.  Persistence of the embryonic notochord, or its sagittal cleavage, may produce a sagittal cleft of the vertebral body dorso-ventrally. The cranial and caudal vertebral end-plates have a funnel shape and in dorso-ventral radiographs, the vertebral body looks like a butterfly.
    • Hemivertebrae is the result of failure (defect or error) of formation of part of a vertebra attributed to persistence of the notochord or lack of ossification.  Likely to occur during the stage of resegmentation and to be related to the abnormal distribution of the intersegmental arteries.
  • Vertebral malformations originating in the fetal period are associated with defects in formation and particularly segmentation. They include:
    • Centrum hypoplasia or aplasia: result in predominantly kyphotic angulation deformities secondary to loss of the vertebral body unilaterally or bilaterally Vertebra: congenital anomaly - radiograph DV  Vertebra: congenital anomaly - radiograph lateral . Dorsal displacement of a severely affected vertebra above the main curvature of the spine may cause severe angulation and spinal cord malformation.
    • Partial or block vertebra: results from partial or complete fusion of 2 or more vertebrae. Often not causing neurological signs, but may occur in cases of angular deformity, stenosis of vertebral canal, instability or ligament hypertrophy.
    • Articular facet aplasia/dysplasia: may result from either dysgenesis of the 2 neural arch centers of ossification or abnormal development of secondary ossification centers. Secondary degeneration and proliferation of the joint capsule and ligamentum flavum can result in stenotic myelopathy and therefore neurologic signs.
    • Spinal stenosis: stenosis of thoracolumbar spine caused by bony proliferation associated with mucopolysaccharidosis VI in cats.
  • Atlanto-axial instability:
    • Hypoplasia of odontoid process causing atlanto-axial instability.
  • Sacrocaudal dysgenesis Sacrocaudal dysgenesis of Manx cats in Manx and Manx-cross cat:
    • Dysgenesis or agenesis of the coccygeal and sacral vertebrae.
    • Due to failure of cranial migration or 'tethering' of the spinal cord as the caudal end of the spinal cord and dural sac fail to stretch normally. 
    • Spina bifida Spina bifida usually present as well.
    • Associated with other abnormalities such as subcutaneous cyst with or without fistulas opening to the dorsal skin with CSF leakage, meningocele, central canal defects, syringomyelia, diastematomyelia.
  • Intermittent trauma or compression of spinal cord Spinal cord: concussion   →   vertebral instability   →   secondary osseous changes   →   spinal cord compression   →   progressive signs.
  • Acute signs from spinal cord compression following vertebral luxation/fracture at site of hemivertebra following sudden jump, fall or trauma.
  • Congenital anomalies of the vertebral column may be associated with anomalies of the spinal cord.
  • Cats with congenital spinal malformation may have concurrent congenital anomalies affecting other systems or other regions of the central nervous system.


  • Usually progressive (weeks/months) but can be acute (hours) or intermittent.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Marioni-Henry K (2010) Feline spinal cord diseases. Vet Clin Small Anim 40 (5), 1011-1028 PubMed.
  • Westworth D R, Sturges B K (2010) Congenital spinal malformations in small animals. Vet Clin Small Anim 40 (5), 951-981 PubMed.
  • Marioni-Henry K, Vite C H, Newton A L et al (2004) Prevalence of diseases of the spinal cord of cats. J Vet Intern Med 18 (6), 851-858 PubMed.
  • Bailey C S & Morgan J P (1992) Congenital spinal malformations. Vet Clin Small Anim 22 (4), 985-1015 PubMed.
  • Jaggy A, Hutto V L, Roberts R E et al (1991) Occipitoatlantoaxial malformation with atlantoaxial subluxation in a cat. J Small Anim Pract 32 (7), 366-372 VetMedResource.
  • Leipold H W, Huston K, Blauch B et al (1974) Congenital defects of the caudal vertebral column and spinal cord in Manx cats. J Am Vet Med Assoc 164 (5), 520-523 PubMed.