Contributors: Laurent Garosi
Species: Canine | Classification: Diseases
- 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.
- Usually asymptomatic - incidental finding on radiograph.
- May be recognized at any age in asymptomatic form.
- Low to moderate cost incurred in diagnostic work-up, eg costs increase if myelography is required to demonstrate cord compression.
- 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.
- 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).
- Typically involve thoracic vertebrae.
- When signs occur, seen as a thoracolumbar myelopathy:
- Hindlimb hyperreflexia.
- Typically acute onset of signs as a result of traumatic/compressive spinal cord dysfunction.
- When signs occur, most frequently see:
- Hindlimb paresis/paralysis.
- Increased spinal reflexes in hindlimbs.
- Fecal/urinary incontinence.
- Pain on palpation of spinal column.
- Abnormal shape vertebrae Radiography: spine.
- T7 vertebrae reported as most commonly affected followed by T8 and T12.
Gross Autopsy Findings
- Spinal instability.
- Vertebral malformation.
- 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).
- Other vertebral anomalies :
- Intervertebral disk disease Intervertebral disk: type 2 herniation (if dog >2 years of age).
- Spinal cord tumors Spinal cord diseases: overview Spine: neoplasia neoplasia.
- Spinal trauma Spine: fracture / luxation Spinal cord: concussion.
- Other developmental anomalies:
- Arachnoid cyst Spine: arachnoid cyst.
- Spinal dysplasia.
- 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.
- 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.
- 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.