Page 74 - May 2017

.. . headshaking is not an uncommon problem, but finding out what is wrong can be very challenging and very expensive.
Headshaking syndrome in horses is a sign of disease, rather than a disease in itself. There are a number of origins, and several veterinarians
have done studies to explore these causes and to find ways to treat them. Headshaking generally comes on suddenly and will continue to occur sporadically.
HEAD
SHAKING
IN HORSES
by Heather Smith Thomas
nose. “There is some kind of irritation in the face or nose area,” she said. “So, one thing I’ve always done as a veterinarian is try to educate people that these horses are not being bad. I think horse owners today have become more aware of this problem and more of them understand that it is a physical problem, not a behavioral problem. These horses can be danger- ous, but they are not intentionally trying to be bad.” When it becomes really serious, the movement may involve the whole head and neck.
“Another sign of headshaking may be rubbing the head and muzzle. This can be constant and vigor- ous. This is not a little gentle rub, it’s like a horrible itch that must be scratched and nothing is making it better. Some of these horses develop sores from the vigorous rubbing,” says Wilkins.
“We don’t know what these horses are feeling because they can’t tell us. There are some similar things in humans, such as people who have trigemi- nal neuritis, an over-activity of the trigeminal nerve. These individuals describe the feeling of tingling, or even very painful sensation, along their nostrils and side of their face.” Where the pain occurs is not neces- sarily where the actual problem is in a horse because the facial nerves in a horse are very long.
“Headshaking is probably primarily related to the trigeminal nerve. It branches off the base of the skull and innervates the skin around the eye and the parts of the face and muzzle that feel sensation. The prob- lem is usually not in the location where we are seeing the itching or pain,” she explains.
A lot of research on headshaking has been done on horses, including by Dr. John Madigan from UC-Davis. One of the causes he first described was equivalent to what people experience who are sun sneezers. “I am a sun sneezer and it can be very uncomfortable,” says Wilkins. “This started for me when I was about 16 years old. Now, I need to wear sunglasses all the time when the sun is bright, otherwise my eyes hurt. I am not comfortable in bright light.
Pamela Wilkins, DVM, PhD, (Diplomate ACVIM, ACVECC, Professor of Equine Internal Medicine, University of Illinois College of Veterinary Medicine) says it can be challenging to figure out the cause. “I tell people that ‘the medicine well is deep.’ We can use mul- tiple diagnostic methods and still come up empty regarding the cause of headshaking. This doesn’t mean we can’t try thera- pies that may be effective.”
Pamela Wilkins, DVM, PhD said headshaking is not a behavioral problem, but rather a physical problem.
Horses with headshaking syndrome exhibit a repetitive, involuntary movement that is generally more vertical than side-to-side. “It’s like a very quick downward flick of the nose and generally looks like something is bothering the horse—an annoyance of some kind,” she says.
One reason Wilkins became interested and involved with this problem was that she had seen headshaking horses as a young person while riding. “Everyone thought this was a behavioral problem, so the horses were punished. Riders would use running martingales, elevator bits, and tack nosebands to keep the horses’ heads in position and keep them from headshaking,” recalls Wilkins.
After she became a veterinarian, she realized that these horses were physically disturbed and were trying to rub or scratch the face, rub their eyes, or blow their
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EQUINE HEALTH