ORTHOPEDICS

LAMENESS VS ATAXIA: Suspect the Unexpected

By Paul Basilio

Differentiating an orthopedic problem from a neurologic one can be a difficult but common issue for lameness practitioners. It’s critical to recognize these issues early on, however, as neurologic deficits can present safety issues for clients with riding horses.

“If you have concern for a neurologic deficit in a riding horse, please make that be known to the client,” said Jackie Christakos, DVM, of the Littleton Equine Medical Center in Colorado. “Falling to the ground on a groomed surface is abnormal. If it happens multiple times, I’m suspicious that something is wrong. When they’re healthy, horses can climb up the side of a mountain on a 100-mile ride. They should not fall while on groomed footing.”

During a Burst Session at the 69th AAEP Convention in San Diego, Dr. Christakos described her process when she suspects a neurological issue in a horse that’s presented for lameness.

During the exam

“Horses don't usually come to me for neurologic dysfunction,” Dr. Christakos explained, “but I end up being suspicious of it when they come to me for lameness.”

While performing the lameness exam, she will look for certain clues that may suggest a neurological component.

Horses don't usually come to me for neurologic dysfunction, but I end up being suspicious of it when they come to me for lameness.

“One of the first things to test is whether there is consistent, blockable limb lameness,” she said. “If it’s present, then I can do my part to take that out of the equation.”

Another clue is if the horse has a “regular” irregular gait, which does not always fit with an orthopedic diagnosis.

“If the horse struggles to hold a gait that should come naturally to it, then that’s a clue,” she explained. “If a horse looks horrible at a walk but looks fine at a trot, then I start to get suspicious of a neurologic problem.”

Another way to differentiate an orthopedic vs neurologic horse is by checking whether the horse’s gait can be thrown off by changing the head position or by walking it down a hill.

“If the horse’s signs are still confusing at the end of the exam, you could do an NSAID [nonsteroidal antiinflammatory] trial and have the horse come back for a re-check,” Dr. Christakos said. “The lameness would be helped more by the NSAID you can probably track the first paragraph on this page and get enough room to spell out NSAID. than the neurologic issues would be. If you can take that out of the equation to make it a little less muddy, then that could be helpful.”

Diagnostics

If she is still suspicious of a neurologic issue after moving through the lameness exam, Dr. Christakos keeps some additional diagnostic tricks up her sleeve.

A post-exercise muscle enzyme evaluation may be illuminating. She will also measure the horse’s vitamin E levels, which can be helpful even if it is not directly related to the horse’s primary issue. Axial skeletal radiographs can also help narrow down her focus.

“Beware of the positive serum EPM [Equine protozoal myeloencephalitis] titer,” she added, noting that a positive serum result doesn’t necessarily signal a clinical problem. “It can be helpful if the test is negative, but otherwise you can’t really use it. This is important to remember for new practitioners because it can be confusing.”

In the end, however, it’s important to remember that the horse may, in fact, have both an orthopedic and a neurologic issue.

“If you are unsure, don’t be afraid to consult with your friendly neighborhood internist—one that has a strong interest in neurology,” Dr. Christakos said. “It can be fun to do these dual exams and to help each other figure out what is going on.” MeV