Contributors: Laurent Garosi

 Species: Canine   |   Classification: Diseases

Introduction Pathogenesis Diagnosis Treatment Outcomes Further Reading


  • Cause: abnormal vertebral development mostly seen in brachycephalic, screw-tailed breeds.
  • Signs: rarely clinically significant, incidental finding on survey radiograph. However, clinical myelopathies associated with butterfly vertebrae are generally traumatic or compressive and occur as a result of malformation or instability of the vertebral column. They are often treatable.
  • Diagnosis: radiography.

Presenting Signs

  • Usually asymptomatic - incidental finding on radiograph.

Age Predisposition

  • May be recognized at any age in asymptomatic form.

Breed Predisposition

Cost Considerations

  • Low to moderate cost incurred in diagnostic work-up, eg costs increase if myelography is required to demonstrate cord compression.

Special Risks

  • Decubital ulcers, urine scald in recumbent animals as a result of spinal instability/spinal cord compression.



  • No known specific cause but associated with screw-tailed breeds, therefore may be genetically transmitted.

Predisposing Factors

  • Presently unknown.


  • Presently unknown.


  • Malformation originating in the embryonic period of development.
  • Butterfly vertebra is a vertebral body/intervertebral disk abnormality which is mesodermal in origin.
  • Result from incomplete intradiskal migration of notochordal material resulting in bificentrum 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.
  • The butterfly vertebra is also characterized by lateral spread of its two halves and compensatory growth of the adjacent normal vertebrae to fill in the funnel-shaped depressions.
  • Improper embryogenesis → abnormal growth and development → some narrowing of vertebral canal → pressure on cord in area.
  • If the vertebral body is very diminutive it may result in kyphotic angulation, especially if associated with centrum hypoplasia.


  • When clinical signs occur, onset is typically acute (hours, days).


Presenting Problems

  • Typically involve thoracic vertebrae.
  • When signs occur, seen as a thoracolumbar myelopathy:
    • Paresis/paraplegia.
    • Hindlimb hyperreflexia.
    • Incontinence.

Client History

  • Typically acute onset of signs as a result of traumatic/compressive spinal cord dysfunction.

Clinical Signs

  • When signs occur, most frequently see:
    • Hindlimb paresis/paralysis.
    • Increased spinal reflexes in hindlimbs.
    • Fecal/urinary incontinence.
    • Pain on palpation of spinal column.

Diagnostic Investigation

  • Abnormal shape vertebrae Radiography: spine.
  • T7 vertebrae reported as most commonly affected followed by T8 and T12.

Gross Autopsy Findings

  • Spinal instability.
  • Vertebral malformation.

Histopathology Findings

  • Traumatic/compression myelopathy may be characterized by varying degrees of petechial hemorrhages, dilated myelin sheaths, macrophage infiltration, and necrosis of the spinal cord (neuronal degeneration, cavitation).

Differential Diagnosis


Standard Treatment

  • Surgical decompression/spinal stabilization if associated with spinal cord compression Spinal surgery: overview.
  • High-quality nursing care:
    • Supportive care.
    • Bladder decompression.
    • Prevention of decubital ulcers/urine scald.


  • Clinical signs.

Subsequent Management


  • Attention to bedding and toilet function in recumbent dogs.


  • Ongoing history.
  • Clinical signs.



  • Good: rarely causes clinical signs.
  • Guarded/good: in dogs requiring surgery that are treated early.

Expected Response to Treatment

  • Look for improvement in clinical signs following surgical intervention.

Reasons for Treatment Failure

  • Incorrect diagnosis.
  • Owner non-compliance.
  • Inadequate nursing care.
  • Spinal trauma not treated early and aggressively.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Gutierrez-Quintana R, Guevar J, Stalin C et al (2014) A proposed radiographic classification scheme for congenital thoracic vertebral malformations in brachycephalic "screw-tailed" dog breeds. Vet Radiol Ultrasound. 55 (6), 585-91 PubMed.
  • Westworth D R, Sturges B K (2010) Congenital spinal malformations in small animals. Vet Clin Small Anim 40 (5), 951-981 PubMed.
  • Bailey C S & Morgan J P (1992) Congenital spinal malformations. Vet Clin North Am Small Anim Pract 22 (4), 985-1015 PubMed.
  • Braund K G, Shores A, Brawner W R Jr. (1990) The etiology, pathology and pathophysiology of acute spinal cord trauma. Vet Med 85 (7), 684-691 VetMedResource.

Other sources of information

  • Braund K G (1994)Clinical Syndromes in Veterinary Neurology.2nd edn. St. Louis. Mosby Year Book. pp 280-281.
  • Oliver, Hoerlein & Mayhew (1987)Veterinary Neurology.pp 203.
  • Bojrab M J (1983)Disease Mechanisms in Small Animal Surgery.2nd edn. Lea & Febiger. pp 954.

Other Sources of Information