There are few things more enjoyable than watching a herd of young horses frolic around a pasture. But when one of the foals looks shaky, incoordinated, and almost wobbly on his feet, this could be a sign of a serious--and sometimes fatal--neurologic problem: cervical vertebral stenotic myelopathy, or wobbler syndrome. At the 2011 Western Veterinary Conference, held Feb. 20-24 in Las Vegas, Nev., Steve Reed, DVM, Dipl. ACVIM, an associate with Rood & Riddle Equine Hospital, in Lexington, Ky., spoke about wobbler syndrome and the scientific advancements that are allowing more "wobblers" to recover and lead a healthy and normal life.
What is Wobbler Syndrome?
Very simply put, horses affected by wobbler syndrome have sustained spinal cord damage that leads to ataxia (incoordination). Most veterinarians say that an affected horse's gaits make him appear as if he's wobbling, hence the common name of the disorder.
Causes of the spinal cord damage can include developmental malformation of the vertebrae in the neck, rapid growth, and trauma. Regardless of the cause, Reed explained, "The most important feature of this condition is a narrowed vertebral canal ... resulting in the compression of the spinal cord." Generally, he added, this compression occurs between the third and seventh cervical vertebrae (C3-C7, located in the neck).
"It's most prevalent in young male horses, especially among Thoroughbreds, Tennessee Walkers, and Quarter Horses," he noted.
Clinical signs are generally detected in affected horses as early as 3 months of age and throughout the first year of life, Reed explained, and include the aforementioned ataxia, impaired movement, and general weakness (which tends to become more apparent when the horse's head is raised, he added).
Typically, veterinarians conduct a neurologic exam, take cervical radiographs and a myelogram (a special X ray of the spinal canal that reveals cervical compression) and test cerebrospinal fluid (to rule out infectious or inflammatory disorders).
There are two treatment options for wobbler syndrome, Reed said: conservative treatment and surgery.
Veterinarians take the conservative treatment approach most commonly in horses less than a year old, allowing the horse to grow out of the problem. This takes a considerable amount of time, and the owner must make extensive management commitments, Reed noted.
"These changes include a reduced level of exercise and careful attention to the diet," he explained. "Dietary changes include avoiding excess weight gain and close observation for a balance of calcium, phosphorus, copper, zinc, and manganese."
A lack of proper nutrient balance, especially in high energy and protein concentrations, might result in a young horse growing rapidly to a large size while not allowing adequate time for normal bone formation.
Reed also recommends supplementing young horses with vitamin E and selenium, especially in areas of the country that have a selenium deficiency. Low selenium concentration might also result in white muscle disease in young foals.
Affected mature horses sometimes can be managed with conservative therapy. Anti-inflammatory medications and a period of limited exercise might allow a horse to eventually return to work, Reed said, adding that corticosteroids can be used to aid in managing the condition for short periods of time.
Surgical treatment of wobbler syndrome 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. This fusion keeps the vertebrae from compressing the spinal cord. Although it can take a horse up to a year to recover from cervical stabilization, Reed said that many horses are able to live healthy lives with normal to nearly normal gaits. But he noted that some horses might still have mild ataxia and "no veterinarian will ever certify the horse as safe" to ride.
Reed spoke fondly of the 1977 Triple Crown winner Seattle Slew as a wobbler syndrome success story. The Thoroughbred stallion underwent two successful cervical stabilizations later in life. The first was completed in 2000 when Slew was 26 years old. The surgery was a success, and he was able to return to breeding mares at Three Chimneys Farm in Lexington. Surgeons repeated the procedure in 2002, when they discovered another area of compression. Again, the procedure was a success, and he returned to Three Chimneys within a week.
While wobbler syndrome is a treatable condition, Reed noted that not every horse is a good candidate for surgery or conservative treatment. In these cases, the most humane option is euthanasia, Reed explained, as these horses generally suffer continuous neurologic problems and become a danger to themselves and their handlers.
Reed also discussed some new wobbler research currently under way. Under the direction of Jamie MacLeod, VMD, PhD, and colleagues at the University of Kentucky (UK) Gluck Equine Research Center, Jennifer Janes, DVM, a postdoctoral scholar at the UK Veterinary Diagnostic Laboratory, is examining bone growth and development of horses that have a stenotic vertebral canal or are "true wobblers."
He noted that researchers have begun examining whether there could be a genetic component to wobbler syndrome. At this time researchers are examining multiple genetic factors that have been suspected to contribute to this syndrome to determine what role they play in the development of the disease. Armed with this information, it might one day be possible for veterinarians, owners, and farm mangers to help prevent this problem in their horses.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.