Test Your Horse's Nervous System

Use these simple checks to evaluate and monitor the state of your horse's vital stimulus-response network.
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Use these simple checks to evaluate and monitor the state of your horse's vital stimulus-response network.

These days, it's easy to find reason to fret about a horse's neurological health. Diseases of the nervous system certainly are not new, but with the increased attention paid to equine protozoal myeloencephalitis (EPM), it doesn't take much for a conscientious caretaker's mind to start spinning. Every stumble or odd step can be misinterpreted as a sign of serious illness. Even the comments of a judge or trainer who's a stickler for absolutely regular paces can make you wonder whether something is neurologically awry with your less-than-perfect horse.

The best way to put your mind at ease is to familiarize yourself with the responses of the normal equine nervous system. You can do this by performing a few simple tests that measure strength, the acuteness of your horse's senses and his coordination--all indicators of neurological health. Don't wait until you suspect trouble to test your horse; knowing his "normal" reactions is important for comparison's sake later on. If your findings seem to indicate that something may be wrong, call your veterinarian to perform a complete diagnostic work-up. You'll also want him to examine your horse if you notice these signs of neurological disease:

  • persistent drooping of one side of the lip or noticeable slackness in one ear
  • uneven sweating patterns
  • unusual behavior, such as head-pressing or circling
  • a consistently unusual stance or odd posture.

Sight
Use the "menace" test--a controlled poking motion made toward an eye--to check your horse's vision. When it is normal, he'll shut his eyelid and perhaps move his head as the finger comes to within an inch of the eye. A horse who doesn't flinch may have impaired vision. Note: Don't wave your hand in front of the eye. The rush of air alone will cause your horse to blink.

Sensation
1. Gently touch various places on your horse's head with the tip of a pencil. A healthy horse will flinch slightly with each touch. No reaction may indicate damage to the nerves that serve that particular spot.

2. Use the pencil tip to trace a line from ears to tail. Press firmly and move the pencil slowly, watching your horse's reaction. A normal horse will move away from the pressure and twitch his "fly shaker" muscles. No reaction may point to a neurological malfunction.

Press a pencil against your horse

Press a pencil against your horse

3a. Run the pencil's eraser firmly along the horse's topline, looking for him to reflexively "sink" under the pressure.

3b. Then, run the eraser along the midline of his belly, watching for him to "lift" his back. A horse who doesn't react to one or both tests may not feel the eraser or may lack sufficient muscle function to respond.

Strength
1. Take hold of your horse's tongue, being careful not to put your fingers in harm's way. A healthy horse's tongue is surprisingly strong and difficult to grasp. A weak tongue can signal nerve damage or slow muscle paralysis.

2. To evaluate the strength of your horse's hindquarters, grab his tail near the dock and lift. A healthy horse will resist, with one possible exception: Mares in heat may not fuss at all. A tail that is easy to lift may indicate weakness caused by neurological disease.

Test your horse

Test your horse

Coordination
1. Lift the horse's head as high as you can and ask him to back up. Backing with a raised head is somewhat difficult, but a neurologically normal horse will be able to do it. If he staggers, refuses to back or sinks on his hind legs, he may be suffering from nervous-system damage.

2. Enlist the aid of a helper to hold your horse's head and keep him from walking forward. Now push him on the shoulder and hindquarters to move him sideways. A healthy horse easily will step over, either crossing his legs or stepping with the far legs first. A horse whose nervous system is impaired will be unable to coordinate his legs to step over smoothly.

3. To test overall coordination, turn the horse in a very small circle. Hold the lead rope in one hand and use your other hand to push his hindquarters over. Make one or two complete circles and then repeat the test, turning the horse in the other direction.

A normal horse will step regularly around the circle, crossing his legs. He won't step on his own feet, lose his balance or stagger.

This article originally appeared in the October 1999 issue of EQUUS magazine.