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14 AAEP FORUM Jennifer Janes, DVM, PhD, DiPl. aCVP TheHorse.com/AAEP-Forum Thehorse.com The horse april 2015 C ervical stenotic myelopathy (CSM), a neurologic disease commonly known as wobbler syndrome, was first reported anecdotally back in the mid-1800s. Skeletal malformations of the neck vertebrae in affected animals lead to narrowing of the cervical spinal canal and subsequent spinal cord compression. Clinical signs primarily include neurolog - ic deficits, with the hind limbs typically more severely affected than the forelimbs. In severe cases, veterinarians might rec - ommend euthanasia for humane reasons and to guard horse and human safety. Equine CSM is a multifactorial disease, meaning it has many causes. High planes of nutrition (overfeeding), increased growth rates, alterations in zinc and cop - per concentrations, and genetic determi- nants could be responsible. Researchers have clearly established the relationship between nutrition, mineral intake, and skeletal development; any disruption in this balance can result in asynchronous (uneven) skeletal growth and possible clinical signs of disease. While we know or suspect that all these factors play a role in CSM development, the exact mecha - nisms leading to clinical disease remain unclear. What we do know is how gender, breed, and age factor into the epidemiol - ogy of this devastating disease. Males are more often affected than females. Breeds such as Thoroughbreds, American Saddlebreds, Warmbloods, and Tennes - see Walking Horses are overrepresented, which means they seem to develop the disease more often than horses of other breeds. And in various studies research - ers have identified the mean age of CSM horses as younger than 2 years, which has prompted veterinarians to categorize CSM as a developmental bone disease. Over the years practitioners have developed approaches for diagnosing CSM. All clinical workups begin with the veterinarian conducting a thorough neurologic exam, looking primarily for signs of ataxia (incoordination). The next step is using radiography to visualize the neck vertebrae. Researchers have defined what's normal or healthy for a neck based on skeletal anatomical measurements at each vertebral site, which helps veterinar - ians identify presumed areas of spinal ca- nal narrowing. Veterinarians can perform myelograms (special radiographs taken after injecting dye into the spinal canal) to see the actual compression. Once a veterinarian diagnoses CSM in a horse, the owner has several manage - ment and treatment options to choose from. More conservative approaches center on dietary modification and anti- inflammatory administration to slow growth rates, reduce swelling of nonskel - etal tissues, and possibly allow vertebral bone remodeling to reduce cord compres - sion. More aggressive approaches involve surgical intervention (e.g., cervical verte - bral fusion) to alleviate cord compression. Developments in diagnostic imaging modalities, such as MRI and CT, have helped veterinarians better characterize the lesions along the entire neck post- mortem. High-resolution images from multiple angles and the ability to visualize the cervical vertebrae, spinal cord, and associated soft tissues together provide powerful data for studying CSM patholo - gy. A combination of imaging modalities, clinical resources, and thorough necropsy examination results are providing new insights for CSM research. Upcoming changes in these imaging units to accom - modate the horse's large size will allow veterinarians to use CT or MRI, where available, to examine CSM cases clinically in the future. Finally, due to rapidly developing tech - nologies, researchers are now examining the equine genome to identify specific genes that may contribute to CSM suscep - tibility. This is an exciting area of research that could have an important impact both on breeding decisions and management of potentially susceptible horses. h Wobbler Syndrome: What We Know and Where We're Headed American Association of Equine Practitioners, 4075 Iron Works Parkway, Lexington, KY 40511 ¥ 859/233-0147 ¥ www.aaep.org AbouT The AuThor Jennifer Janes, DVM, PhD, Dipl. ACVP, is assistant professor of anatomic pathology at the University of Kentucky Veterinary Diagnostic Laboratory, in Lexington. Note the difference between the MRI image showing a normal spinal cord on the left and the one showing cord compression on the right. CourTesy Dr. Jennifer Janes