Walking On Volume 2, Issue 3, March 2015 | Page 10
For the Health of It
Where Are We Headed
with Wobbler Syndrome?
Reprinted from the January 2015 issue of Equine Disease Quarterly
Cervical stenotic myelopathy (CSM), commonly known as
wobbler syndrome, is a neurologic disease characterized by
malformations of the neck vertebrae. This leads to narrowing
of the cervical spinal canal and subsequent compression of
the spinal cord. The cord compression manifests clinically as
neurologic deficits, typically with the hind limbs being more
severely affected than the forelimbs. Depending on the severity
of the horse’s deficits, euthanasia is often elected for humane
and horse and human safety reasons.
Equine CSM is considered to be a multifactorial disease
with high planes of nutrition, increased growth rates, alterations in zinc and copper concentrations, and genetic determinants implicated in disease development. Although all these
factors are known or suspected to play a role, the exact mechanistic details that lead to clinical disease are still unclear.
Gender, breed, and age factors are well represented in the
current knowledge base of this devastating disease. Males are
more often affected than females. Breeds such as Thoroughbreds, American Saddlebreds, Warmbloods, and Tennessee
Walking Horses are overrepresented in the identification of
the syndrome. Various studies have identified the mean age of
CSM horses as less than 2 years leading to the categorization of
CSM as a developmental bone disease.
Over the years, assessment methods and analytical approaches for accurate clinical diagnosis of CSM have been developed. All clinical workups begin with a thorough neurologic
examination looking primarily for signs of ataxia. The next
step is visualization of the neck using radiography. Standard
ratios based on skeletal anatomical measurements have been
defined at each intervertebral site to identify presumptive areas
of spinal canal narrowing. For visualization of actual spinal
cord compression, myelograms can be performed.
Once a diagnosis of CSM is made, several management and
treatment options are available. More conservative approaches
center on dietary modification and anti-inflammatories to slow
growth rates, reduce swelling of non-skeletal tissues, and possibly allow vertebral bone remodeling to reduce cord compression. More aggressive approaches involve surgical intervention
to alleviate cord compression via cervical vertebral fusion.
Despite all that is known, important questions still remain about wobbler syndrome. Recent research at the Gluck
Equine Research Center has focused on CSM. Developments
in diagnostic imaging modalities, such as magnetic resonance
imaging (MRI) and computerized tomography (CT), enable
10 • Walking On
the characterization of lesions along the entire neck. High-resolution images from multiple angles and the ability to visualize
the cervical vertebrae, spinal cord, and associated soft tissues
together provide powerful data to study and understand CSM
pathology. The combined resources of imaging modalities,
clinical resources, and thorough necropsy examinations are
providing new insights for CSM research. Although currently
used in the research settings, changes in these imaging units to
accommodate the size of the horse will allow for the possible
use of CT or MRI for clinical diagnosis in the future.
The role of inherited genetic determinants is a long-standing question. Due to rapidly developing genomic technologies,
studies are now being conducted to investigate the equine
genome to identify specific genes that may contribute to CSM
susceptibility. This is an exciting area of research that could
have an important impact on breeding decisions and management of potentially susceptible horses.
CONTACT
Dr. Jennifer Janes, [email protected]
University of Kentucky
Lexington, Kentucky