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Spine: cervical vertebral malformation (CVM)

pequis
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Synonym(s): Wobblers, Cervical vertebral stenotic myelopathy, CVSM, CVM, Cervical compressive myelopathy, CCM


Introduction

  • A developmental condition of well-fed foals and young horses, especially male Thoroughbreds.
  • Condition may have hereditary component.
  • Cause: abnormalities in the vertebral bodies, dorsal lamine and/or articular processes   →   dynamic or static stenosis of the vertebral canal   →   focal compression of the spinal cord.
  • Signs: gait abnormalities, proprioceptive abnormalities and weakness.
  • Diagnosis: neurologic examination, plain radiography, and contrast myelography of the trunk and limbs, computed tomography, ruling out other causes of neurologic disease.
  • Treatment: conservative or surgical depending upon severity of condition.
  • Prognosis: dependent on severity of neurologic signs and intended use of horse.

Pathogenesis

Pathophysiology

  • Progressive spinal cord compression   →   clinical signs.
  • Osteochondrosis-like lesions have been seen on the articular surfaces and vertebral body growth plates in some affected horses.
  • 2 syndromes are seen: dynamic stenosis and static stenosis.

Dynamic stenosis

  • Extension or flexion of neck   →   compression.
  • C3-C4 most commonly affected site, followed by C4-C5.
  • Seen mostly in weanlings, yearlings and 2 year-olds. Most commonly diagnosed between 8 and 18 months.
  • Radiographs taken in neutral position may appear normal.

Static stenosis

  • Stenotic canal always present, but may be exacerbated by flexion or extension.
  • C5-C7 usually affected.
  • Wedging of cranial aspects of vertebral bodies   →   narrowing of vertebral canals   →   cord compression.
  • Malformation of articular processes and remodeling of intervertebral joints   →   cord compression.
  • Horses 1-4 years old, often diagnosed in training; can also be diagnosed in horses 5-10 years of age.
  • Soft tissue compression secondary to synovial proliferation.
  • Damage to ascending spinal cord tracts   →   proprioceptive abnormalities on all four legs   →   manifest as ataxia (occasionally as hypermetria).
  • Damage to descending spinal cord tracts   →   tetraparesis (particularly evident on doing a 'tail pull'), stiffness or hypometria.

Timecourse

  • Variable.
  • Usually progressive.
  • Onset may be acute (traumatic incident) or insidious.
  • Confirmed cases rarely resolve spontaneously.

Epidemiology

  • Thoroughbreds and Quarterhorses most commonly affected.
  • Males overrepresented.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Janes J G et al (2014) Comparison of magnetic resonancy imaging with standing cervical radiographs for evaluation of vertebral canal stenosis in equine cervical stentoci myelopathy. Equine Vet J 46 (6), 681-686 PubMed
  • Prange T, Carr E A, Stick J A et al (2012) Cervical vertebral canal endoscopy in a horse with cervical vertebral stenotic myelopathy. Equine Vet J 44 (1), 116-119 PubMed.
  • Birmingham S S W, Reed S M, Mattoon J S & Saville W J (2010) Qualitative assessment of corticosteroid cervical articular facet injection in symptomatic horses. Equine Vet Educ 22 (1), 77-82 VetMedResource.
  • Martinelli M J, Rantanen N W & Grant B D (2010) Cervical arthropathy, myelopathy or just a pain in the neck? Equine Vet Educ 22 (1), 88-90 Wiley Online Library.
  • Hahn C (2006) The wobbly horse: differential diagnoses. In Pract 28 (1), 8-13 VetMedResource.
  • Nout Y S & Reed S M (2003) Cervical vertebral stenotic myelopathy. Equine Vet Educ 15 (4), 212-223 VetMedResource.
  • Moore B R et al (1994) Assessment of vertebral and canal diameter and bony malfunctions of the cervical part of the spine in horses with cervical stenotic myelopathy. Am J Vet Res 55, 5-13 PubMed.
  • Moore B R, Reed S M, Biller D S et al (1994) Assessment of vertebral canal diameter and bony malformations of the cervical part of the spine in horses with cervical stenotic myelopathy. Am J Vet Res 55 (1), 5-13 PubMed.
  • Moore B R, Reed S M & Robertson J T (1993) Surgical treatment of cervical stenotic myelopathy in horses, 73 cases (1983-1992). JAVMA 203 (1), 108-112 PubMed.

Other sources of information

  • Alcott C A (2015) Transcranial Magnetic Motor Evoked Potential Latencies in Axon Loss in Equine Cervical Stenotic Myelopathy. In: Proc ACVIM Forum.
  • Reed S M, Saville W J A & Schneider R K (2003) Neurologic Disease: Current Topics in-depth. In: Proc 49th AAEP Convention. pp 243-258.
  • Mayhew I G (1989) Large Animal Neurology; A Handbook for Veterinary Clinicians. Lea & Febiger, USA.

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