The Question

Q My 7-year-old Quarter Horse gelding has suddenly become unsteady in his hind end. He can’t balance well with his hind legs, and sometimes almost falls down. He’s eating normally and doesn’t seem in pain. A test for EPM came back negative. A chiropractor once told me my gelding has some misaligned vertebrae in his neck, but we haven’t done X-rays. I can’t ride him like this, of course, and the fact that he can’t keep his balance makes him a danger to himself and to people who work around him. What could be wrong, and can anything be done?

LAURIE SHEA, Colorado

The Answer

A Balance problems often indicate a neurological condition. I’d recommend a full neurological exam performed by a board-certified internal medicine specialist (a veterinarian with additional training in equine neurological disease). Exam results will help pinpoint the location of any lesion and allow the vet to decide on further diagnostic testing.

With an acute onset, equine herpes myeloencephalopathy needs to be ruled out. Horses with this condition usually have hind-limb ataxia (difficulty balancing and walking) along with a fever and urine dribbling. West Nile virus can also cause hind-limb ataxia; have your horse tested for this disease immediately if he hasn’t been vaccinated.

Given that your horse is older than 3, equine degenerative myeloencephalopathy, another potential cause, is highly unlikely. (A low vitamin E level would be suggestive of the disease.) Equine protozoal myeloencephalitis (EPM) also causes spinal cord ataxia in horses, and I’d recommend a review of the EPM testing you’ve already had done. The best EPM test to run, because it’s more predicative of active disease, is a cerebrospinal fluid (CSF) sample with a paired serum titer (blood test).

Another common cause of hind-limb ataxia is cervical vertebral compressive myelopathy, or “wobbler’s” syndrome. There are two types of wobbler’s. Type I affects rapidly growing horses and is common in Thoroughbreds, Warmbloods, and Quarter Horses. This is a developmental disease that causes problems within the spinal canal; the instability of cervical bones causes the cord to become compressed. The compression causes damage to the spinal cord that transmits nerve signals to the hind legs. Type II affects older horses and stems from arthritis of the vertebrae joints.

X-rays are best to diagnose the disease. Standing X-rays can be done in the field, but at an equine hospital is better. The gold standard in diagnosing wobbler’s is a myelogram, done under general anesthesia. A needle is placed in a space that surrounds the spinal cord, a CFS sample is taken to be analyzed, and a contrast agent is injected into the spinal cord. X-rays are then taken, and the contrast material helps determine if compression is present within the spinal column. (See box for potential treatments for wobbler’s syndrome.)

The bottom line: A thorough work-up to consider each of these possibilities is essential to give your horse the best possible chance of getting appropriate treatment.

JONATHAN A. YARDLEY, DVM
Assistant Professor, Clinical
Equine Field Services
College of Veterinary Medicine
Ohio State University