Disease Du Jour: Equine Neurologic Exam

So many things can cause neurologic signs in horses, but a good veterinary exam can help discover the cause of the problem.
neurologic Paint horse in field
So many things can cause neurologic signs in horses, but a good veterinary exam can help discover the cause of the problem. Arnd Bronkhorst Photography

“A lot of times, being faced with a neurologic horse can be daunting,” said Emily Schaefer, VMD, DACVIM-Large Animal, on Equine Neurologic Exams, in Episode 86 of the Disease Du Jour podcast.

Schaefer is a Clinical Assistant Professor of Internal Medicine at the Marion duPont Scott Equine Medical Center at the Virginia-Maryland College of Veterinary Medicine. She is currently a Fellow in Equine Emergency & Critical Care at The Ohio State University. Her research interests include emergency and critical care, acute kidney injury, the acute equine abdomen and equine neonatology. Schaefer is also a permitted treating veterinarian with the FEI.

She recommends even before going to the farm to see the horse or having it brought to you that you get an accurate history—which includes a vaccination history—a travel history and any recent exposure to other horses.

“That will dictate how you assess the horse and even help you decide if you want to bring the horse to the hospital or see it on the farm to avoid spreading disease in your clinic,” Schaefer said.

She said in her list of differential diagnoses in the area where she practice, the first possibility would be EPM. “The time of year or region might mean you think about West Nile virus. Rabies is rare (but always a concern),” she said.

She said once you get to the farm, first talk to the owner. Ask them how they describe the presentation and what their complaint is. “It might not be neurologic at all!” said Schaefer.

When you first arrive, get the “big picture,” said Schaefer. “Before taking the horse out of the stall or paddock, look at the horse’s environment. Assess his mentation.Is he head pressing? What is his posture? What are his eyes and ears telling you?

“Look for facial symmetry,” she continued. “Can the horse prehend food? How is the horse standing? Is his tail cocked or is a leg pointing or is he leaning on the wall? Does he have a droopy lip or eyelid? How is his eyeball positioning?”

She said neurologic signs in a performance horse might be subtle, but sometimes it is an emergency where the horse can’t stand.

Schaefer said knowing some of these clinical signs can help a veterinarian determine if there is brain stem involvement or where the location is in the CNS that is affected.

Schaefer recommended doing a cervical facial reflex and examining the trunk and neck to ensure nerves are functioning properly.

“Look at the hips and how the horse is standing,” she recommended. “Asymmetry in the neck or hip van help you localize the affected area.”

She emphasized the safety of the horse and handler when doing a neurologic exam in-hand. That exam will include walking a straight line and looking for foot placement and trunk sway.

“Ataxia is when the horse has an irregular, irregular gait,” she defined.

After addressing the horse on a straight line, she recommends lifting the horse’s head high enough that it can’t use “visual compensation” if it has neurologic deficits. “The front legs will look ‘floaty’ or they might ‘pace’ instead of walk normally,” she said. “Or they might just refuse to move!”

You can also lift the horse’s head when it is walking up or down hills to get even more information.

After walking in straight lines, Schaefer asks the horse to walk in a serpentine. For this she is looking for foot placement, the pivot, and circumduction of the outside hind leg on the turn.

If possible, she watches the horse go in small, 5-meter circles. “I want the horse to walk forward not pivot,” she said. With this she looks for interfering and circumduction of the hind legs.

If veterinarians want to use a tail pull on a straight line, “tug the tail as the leg is about to hit the ground,” she said. “It can be a subtle reaction or recovery, or they an interfere or nearly fall.”

Another possibility for a neurologic exam is to use changes in surface or ask the horse to walk over a small obstacle. “I put a black rubber mat and serpentine the horse over the mat,” she said. “This tells me if the horse is not judging where it is putting its feet.”

In this podcast, Schaefer talks about a neurologic scale (like a lameness scale). She talks about what clinical signs she sees and what those mean as far as location of the damage in the CNS.

Schaefer talks about EPM testing and what that means and how to explain tests to horse owners.

She talks about older horses and radiographing their necks to look for arthritis or trauma.

Botulism is another neurologic disease that she discusses in the podcast.

Vitamin E deficiencies can cause neurologic signs in horses, she stated. “It’s not uncommon if you have subtle spinal ataxic horse that you can’t find another diagnosis that on post-mortem you find it has a Vitamin E deficiency,” said Schaefer. “The deficiency early in life can develop into neurologic disease when the horse develops and is in training at 6-8years old! It’s a permanent neurologic issue, but if you test the horse, it has normal Vitamin E levels.”

She reminded breeders that pregnant mares, foals and young horses need to have sufficient Vitamin E during those formative times in a young horse’s life or it can have effects years down the road.

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