Canis ISSN: 2398-2942

Spine: hemivertebra

Synonym(s): Wedge shaped vertebra

Contributor(s): Kyle Braund, Laurent Garosi

Introduction

  • Most clinically significant vertebral anomaly.
  • Screw-tailed breeds.
  • Cause: developmental anomaly.
  • Signs: scoliosis, kyphosis, lordosis.
  • Most common in the thoracic area → if pressure on cord → neurological signs.
  • Diagnosis: radiography, CT, MRI.
  • Treatment: surgical stabilization +/- decompression if appropriate.
  • Prognosis: signs may deteriorate as animal grows.

Pathogenesis

Etiology

  • Inherited as an autosomal-recessive disorder in some lines of German Short-haired Pointers.

Specific

  • Acetohydroxamic acid (used to treat struvite)in utero.

Pathophysiology

  • 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 or resegmentation and to be related to the abnormal distribution of the intersegmental arteries.
  • Improper embryogenesis → abnormal growth → vertebra malformation:
    • Hemi-metameric displacement of somites → left and right hemivertebrae → scoliosis.
    • Failure of ossification → unilateral, dorsal or ventral hemivertebrae.
    • Unilateral hemivertebra → scoliosis.
    • Dorsal hemivertebra → kyphosis.
    • Ventral hemivertebra → lordosis.
  • Intermittent trauma or compression of spinal cord -> vertebral instability → secondary osseus changes → spinal cord compression → progressive signs.
  • Acute signs from spinal cord compression following vertebral luxation/fracture Spine: fracture / luxation at site of hemivertebra following sudden jump, fall or trauma.
  • There is an important correlation between neurologic signs and kyphosis and subluxation. However, vertebral canal height does not differ between normal dogs and dogs with thoracic hemivertebra.
  • Hemivertebrae may be single or multiple and may be associated with other vertebral malformations producing complex spinal malformations.
  • May be associated with malformations of neural tissue (spinal dysraphism Spine: dysraphism spinal arahcnoid cyst Spine: arachnoid cyst...)

Timecourse

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

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

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.
  • Moissonnier P, Gossot P, Scotti S (2011) Thoracic kyphosis associated with hemivertebra. Vet Surg 40 (8), 1029-1032 PubMed.
  • Westworth D R, Sturges B K (2010) Congenital spinal malformations in small animals. Vet Clin Small Anim 40 (5), 951-981 PubMed.
  • Jeffrey N D, Smith P M, Talbot C E (2007) Imaging findings and surgical treatment of hemivertebrae in three dogs. JAVMA 230 (4), 532-536 PubMed.
  • Thilagar S, Gopal M S, Mohammed M S D M (1998) Hemivertebra in a dog. Ind Vet J 75 (2), 163-164 VetMedResource.
  • Bailey C S & Morgan J P (1992) Congenital spinal malformations. Vet Clin North Am Small Anim Pract 22 (4), 985-1015 VetMedResource.
  • Kirkberger R M (1989) Congenital malformation and variation of the lumbar vertebrae in a dog. J Sth Afr Vet Assoc 60 (2), 111-112 PubMed.
  • Kramer J W et al (1982) Characterization of heritable thoracic hemivertebra of the german short-haired pointer. JAVMA 181 (8), 814-815 PubMed.
  • Bailey C S (1975) An embryological approach to the clinical significance of congenital vertebral and spinal cord abnormalities. JAAHA 11 (4), 426-434 VetMedResource.
  • Done S H, Drew R A, Robins G M, Lane J G (1975) Hemivertebra in the dog - clinical and pathological observations. Vet Rec 96 (14), 313-317 PubMed.

Other sources of information

  • Colter S (1993) Disease Mechanisms in Small Animal Surgery. Bojrab M J. 2nd edn. Lea & Febiger. pp 953-955.


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