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Cervical Vertebral Malformation, CVM

Synonyms: Cervical Vertebral Stenotic Myelopathy, Wobbler's Syndrome

Any disease process that causes compression of the spinal cord in the neck causes CVM (Cervical Vertebral Myelopathy), also known as Wobbler’s Syndrome.

The long nerve tracts that run the length of the spinal cord are responsible for conveying the position of the hind and front limbs to the brain. If one is looking at the cross section of the spinal cord, the nerve tracts responsible for communication with the hind limbs are positioned on the outside of the circle. Thus, anything pushing into the spinal cord from the outside affects them more than the forelimbs.

CVM can take several forms. It is seen in younger horses as a malformation of adjacent neck vertebrae that causes compression of the spinal cord. It causes signs of weakness and wobbliness (ataxia), which is usually worse in the hind limbs.

In older horses, compression is also caused by bone buildup on the inter-vertebral joints as a result of chronic arthritis. As in humans, disc protrusion can put pressure on the spinal cord, causing similar signs.

Severity of CVM is graded from 1 (very mild deficit that can only be detected by a trained observer), to 5 (horse is unable to rise on its own).

Diagnosis requires radiographs of the cervical spine (the neck), and confirmation usually requires myelogram.

Treatment includes reduction in expectation, injection of vertebral joints, feeding and management changes, and surgery. In serious cases of cord compression, surgery is often the only option.

Prognosis & Relevant Factors

Prognosis depends on the age of the horse, the severity of the compression, the duration of compression (and degree of resulting spinal cord damage) and the related degree of wobbliness (ataxia).

Generally, compressive spinal disease treated without surgery has a poor prognosis. In many cases, wobbliness worsens over time.

Horses treated with surgery usually improve significantly. Those diagnosed and treated early in the disease process do better. Ataxia should be expected to improve significantly but may not resolve completely. There are many cases of successful subsequent performance careers in horses that have had surgery.

QUESTIONS TO ASK MY VET

  • What improvement can be expected with surgery?
  • Will my horse likely return to prior levels of performance following surgery?
  • What other treatment options should I consider?
  • PREVENTION

    To the extent that this problem may be a genetic defect, prevention is based on selection of horses with genetic lines that do not carry this trait.

    Nutritional management of growing horses (avoiding over-feeding of growing horses and too rapid growth that results) may help reduce the likelihood of this condition.

    Prevent injury of the spinal cord of the neck by teaching horses not to set back against pressure when tied.

    Helpful Outside ResourcesCredible Equine Health Information on the Internet

    Author: Doug Thal DVM Dipl. ABVP

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