Cervical vertebral compressive myelopathy is a common cause of general proprioceptive ataxia and paresis in horses.1–4 The disease results from a diverse set of lesions, such as vertebral canal stenosis, vertebral body tipping, and articular process osteophytosis, which alone or in combination lead to extradural spinal cord compression.2–7 Factors involved in development of CVCM likely include vertebral column malformation, osteochondrosis of the articular processes, copper deficiency, dietary zinc excess, high carbohydrate ration, vertebral column instability, and chronic microtrauma.5,8–13
Male horses seem to be at increased risk for CVCM. In a series of reports on CVCM, 125 of 150,14 21 of 25,15 19 of 22,16 and 9 of 1117 horses were male (castrated or sexually intact). The reasons for this apparent overrepresentation are unclear, although increased risk for cervical vertebral column microtrauma caused by sex-based differences in use or activity is a possible explanation. In humans18,19 and dogs20,21 with cervical spondylotic myelopathy, a disease likely analogous to CVCM, a similar male predilection has been suspected.
A variety of breeds have been described as being predisposed to CVCM, including Thoroughbred, Quarter Horse, European Warmblood, and Tennessee Walking Horse.2,14,22,23 With the exception of work done by Mayhew et al2 and Levine et al,16 studies on CVCM have lacked control groups derived from the same hospital for purposes of assessing the significance of apparent breed overrepresentations. For example, the finding that most horses with CVCM diagnosed at an institution are a particular breed might simply reflect the preponderance of that breed in the population of horses referred to that center and not a true breed predilection.24 A study25 comparing CVCM-affected horses (n = 177) with ataxic horses without myelographic compression of the spinal cord (129) did not reveal differences in breed among groups. Thus, evidence regarding breed predilection for CVCM is conflicting. Moreover, explanations for possible breed predispositions to CVCM have been largely speculative, although different use and genetic profiles have been suggested.5,7,26
Traditionally, CVCM is thought to be most common in young horses. Although this is a widely held belief, few studies have investigated age predispositions in CVCM. Age was described as ≤ 4 years in 147 of 150 horses14 and 23 of 25 horses15 in 2 reports, although in 1 smaller study,27 only 8 of 13 horses were ≤ 4 years of age. In a study of 306 ataxic horses, Pageorges et al25 found that although 66% were < 3 years of age, horses with CVCM were no different in age, compared with those with other causes of myelopathy. Recently, CVCM was described in a subset of 22 horses > 4 years of age.16 It has been speculated that the development of CVCM in older horses may relate to chronic microtrauma to the vertebral column, whereas the disease in younger horses may directly result from malformation, nutritional imbalance, and developmental orthopedic disease.5,16
To the authors' knowledge, the association of CVCM with sex, breed, and age of horses has not been systematically evaluated in a large population of horses with CVCM. Thus, the purpose of this case-control study was to use data from horses registered in the VMDB to determine whether the distributions of sex, breed, and age of horses differed significantly between horses with CVCM (case horses) and a group of horses from the same hospitals admitted during the same time period as cases (control horses).
Cervical vertebral compressive myelopathy
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