Experts disagree on horses with incoordination

A trip to the veterinarian may prove fatal to a horse, even if it is not necessary to put the animal down. In Europe if the horse is found to be ataxic, which is most often due to the disease 'wobbler syndrome', the horse is likely to be put down immediately. If a horse suffers from this disease, putting it down can be a necessity, as the animal can be dangerous to ride and handle. But now new research from the University of Copenhagen and the Royal Veterinary College in the UK shows marked disagreement among experts about when a horse is ataxic and severity of the ataxia. It is particularly a problem if the ataxia is subtle, as this makes it more difficult to assess.

"It is a problem for both the horse and the owner if the specialists disagree. A horse which could potentially recover might be put down, as an ataxic horse eventually becomes a hazard to the owner due to the risk of a fall during riding or handling," says Emil Olsen, DVM, PhD from the Department of Large Animal Sciences, who headed up the new research.

The results were recently published in the prestigious Journal of Veterinary Internal Medicine.

Ataxia caused by Wobbler syndrome affects one in 100 horses, and is one of the greatest sources of missed training days and frustration for horse owners and veterinarians alike. The disease occurs due to pressure on the cervical spinal cord, which can be diagnosed in humans and small animals by MRI or CT scans - but there are no scanners with a diameter large enough to accommodate a horse's neck and shoulders. The foundation of the veterinarian's assessment is therefore the clinical examination of small changes and irregularities in the horse's gait.

"In this study, specialists in the areas of large animal internal medicine , specialists in equine surgery, and residents evaluated the gait during a neurological examination of 25 horses, and then videos of the horses. They completed a questionnaire, and based on their responses we could see that there was wide disagreement on whether or not they believed a horse was ataxic, and particularly on the severity of the ataxia," says Dr. Emil Olsen.

Horse owners and veterinarians often assume horses with mild ataxia are mildly lame, allowing ataxia to progress to the point of sudden falls during riding or handling. If the disease is discovered when the horse is a foal, treatment options can include restrictive feeding, and at all ages there is a surgery to stabilise the neck by fusing the cervical vertebrae. For horses with ataxia caused by articular process joint (facet joint) osteoarthritis, injecting steroids into the joint can improve the horse's condition for a period of time.

"We hope that our findings will lead to the establishment of clearer definitions for what constitutes normal and abnormal gait patterns in horses, and the relationship between spinal cord disease and ataxia. This could lead to greater agreement among specialists and practising veterinarians. The current disparity also raises the need for quantitative diagnostics, using equipment that can measure the horse's movements in detail."

If you have a horse you suspect is ataxic, please contact your veterinarian for further advice.

Facts about ataxia

Ataxia is Greek for 'incoordination,' which is a clinical sign of neurological disease. One of the most common causes in Europe is Wobbler syndrome, or cervical vertebral malformation-malarticulation (CVM, CVSM, CSM). Wobbler syndrome is caused by compression of the spinal cord by either growth abnormalities or facet joint osteoarthritis in the older horse.

There were over 70,000 registered horses in Denmark in 2012, so around 700 of these can be expected to develop ataxia at some point in their life. The disease can be a major hazard to owners, riders and other horses, because ataxic horses can fall suddenly during riding or handling. The special patterns of movement, which arise in connection with ataxia, are easier to diagnose at advanced stages of the disease, and it is currently not possible to diagnose mild degrees of ataxia with certainty. MR or CT scans can be performed on humans, dogs and cats to determine if there is pressure on the spinal cord, but there are no MR or CT scanners large enough to accommodate a horse's neck and shoulders. The foundation for the diagnosis is therefore the veterinary surgeon's clinical examination.

The experts who were asked to assess the horses looked at their patterns of movement and the results of neurological examinations. An equine neurological examination looks at the functioning of the brain's reflexes and senses and the ability to coordinate movement.

The horses were assessed using a five-point grading scale, with 0 being normal and 4 indicating such an advanced stage of ataxia that the horse requires support to walk. In particular, there was disagreement between grades 0, 1 and 2, with some specialists disagreeing by two grades – one specialist might view a horse as normal, while another viewed it as having moderate ataxia.