Equis ISSN 2398-2977
Spine: cervical vertebral malformation (CVM)
Synonym(s): Wobblers, Cervical vertebral stenotic myelopathy, CVSM, CVM, Cervical compressive myelopathy, CCM
Contributor(s): Robert J MacKay, Kate Hepworth-Warren
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 Get al(2014)Comparison of magnetic resonancy imaging with standing cervical radiographs for evaluation of vertebral canal stenosis in equine cervical stentoci myelopathy.Equine Vet J46(6), 681-686 PubMed.
- Prange T, Carr E A, Stick J Aet al(2012)Cervical vertebral canal endoscopy in a horse with cervical vertebral stenotic myelopathy.Equine Vet J44(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 Educ22(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 Educ22(1), 88-90 Wiley Online Library.
- Hahn C (2006)The wobbly horse: differential diagnoses.In Pract28(1), 8-13 VetMedResource.
- Nout Y S & Reed S M (2003)Cervical vertebral stenotic myelopathy.Equine Vet Educ15(4), 212-223 VetMedResource.
- Moore B Ret 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 Res55, 5-13 PubMed.
- Moore B R, Reed S M, Biller D S, Kohn C W & Weisbrode S E (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 Res55(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).JAVMA203(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.Philadelphia. Lea & Febiger.