Cervical vertebral stenotic myelopathy (CVSM) is an important disease of Thoroughbred horses in which compression of the spinal cord in the neck leads to incoordinated gait. Affected horses are often described as “wobblers”.
Two types of the condition have been recognised. In the first type (dynamic stenosis), compression occurs only when the horse flexes or extends the neck. It is caused by malformation of the vertebrae and tends to affect the third and fourth (C3-C4) or fourth and fifth (C4-C5) cervical vertebrae. This type is more commonly seen in younger animals (yearlings).
In the second type, (static stenosis) the spinal cord is compressed by proliferative bone resulting from osteoarthritis. This form occurs most commonly between C5-C6 and C6-C7, and is seen in older animals.
But how common is CVSM? Research published recently in the Veterinary Record, looked at the prevalence of the condition.
The study, from the University of Glasgow, was based on records from four breeding establishments - three European Thoroughbred stud farms (936 foals) and one farm in USA (353 foals) - over a 7 year period.
During that time there were 13 cases of Type 1 CVSM, (dynamic stenosis); 5 horses with Type 2 CVSM (static stenosis) and 5 horses in which the Type could not be determined. Overall, 1.3% of the animals were found to be affected.
The average age at which signs of the condition became apparent differed. Horses affected with dynamic stenosis were noticed at a younger age than were those with static stenosis. Type 1 (dynamic stenosis) was diagnosed typically in yearlings (Mean 433days old - about 1y 2 months.) Horses affected with the stenotic compression were diagnosed later - (mean 1188d -about 3years 3 months)
The researchers also found that male horses were significantly more likely to be affected (17 male to 6 female), which agreed with previous studies.
“CVSM is an important disease of Thoroughbred horses and leads to wastage in the thoroughbred industry through the inability to race and the loss of affected horses” the report's authors conclude.
They suggest that “further investigations of the prevalence of CVSM in populations of thoroughbreds and other breeds and determination of risk factors for the disease are warranted.”
Prevalence of cervical vertebral stenotic myelopathy in a population of thoroughbred horses.
Oswald J, Love S, Parkin TDH, Hughes KJ.
Vet Rec (2010) 166, 82-83