The neurologic condition cervical vertebral stenotic myopathy (CVSM, commonly known as wobbler syndrome) is much less common in older horses than it is in young, growing animals. But according to one clinician, this condition should be on all veterinarians’ differential diagnoses list when evaluating an aged horse presenting with neurologic signs and/or neck pain.

At the 2013 Western Veterinary Conference, held Feb. 17-21 in Las Vegas, Nev., Laurie Beard, DVM, MS, Dipl. ACVIM, associate clinical professor at Kansas State University’s College of Veterinary Medicine, presented a review of CVSM in aged horses.

Horses affected by CVSM essentially have a damaged spinal cord. The major causes of spinal cord damage include cervical (neck) vertebrae malformation or trauma.

“The exact pathogenesis of CVSM in older horses is unknown and likely different than younger horses,” Beard said. She said older horses are more likely to have lesions located in the caudal cervical vertebral column (near the base of the neck), between the vertebrae C5 and C6 or C6 and C7. She noted that some studies suggest biomechanical loading related to “wear and tear” could contribute to lesions. Additionally, she said, articular process osteophytosis (bony remodeling) is a common finding in older horses with CVSM.

Beard said common clinical signs associated with CVSM in older horses include:

• Spinal ataxia (incoordination), generally symmetric with the hind limbs affected more than the front limbs. Beard noted that in some cases, however, mature horses with CVSM might appear more lame than ataxic;
• Neck pain or stiffness;
• Neck arthritis; and
• Decreased appetite.

Beard said veterinarian frequently use standing cervical radiographs to diagnose CVSM in mature horses. However, if cervical radiograph results are inconclusive, a myelogram, considered the gold standard CVSM test, might be required. This procedure involves injecting dye into the spinal canal before taking a set of radiographs to evaluate the spinal column’s width and to identify possible sites of compression.

Treatment options for mature horses diagnosed with CVSM include:

• Anti-inflammatory drugs (both steroidal and non-steroidal, depending on disease severity);
• Natural vitamin E supplementation (Beard explained that vitamin E is an antioxidant that could act as an anti-inflammatory in horses with CVSM);
• Cervical facet steroid injections (this procedure must be repeated every six months or so, but can reduce pain and soft tissue swelling); and
• Surgical correction (which typically consists of fusing the affected vertebrae–the movement of which causes the spinal cord compression–together using a metal implement called a “basket” in a surgical procedure called cervical stabilization).

The prognosis for for return to work in mature horses with CVSM is variable and depends on the degree of ataxia present, Beard said.

“A horse with mild clinical disease that is a trail riding horse (or low-level performance horse) probably does have a reasonable chance of still performing,” she said. “However, higher level performance horses probably will not be able to perform at the level they were.”

Additionally, horses used for pleasure riding are more likely to have a good prognosis for full return to athletic function than higher performance athletes, she said.

Take-Home Message

Although it’s commonly thought of as a young horse disorder, Beard stressed that veterinarians should consider CVSM as a differential diagnosis in any horse with spinal ataxia. Prognosis for return to work depends on the degree of ataxia present, but many horses show improvement with medical management, she said.