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headshaking can have many other causes, but this behavior can be the earliest clinical sign of something very serious.
Headshaking may include constantly and vigorously rubbing the head and muzzle.
with the endoscope,” she continued. “Skull radiographs can also help with a THO diagno- sis. Routine bloodwork is also helpful.” Various diagnostic techniques may give clues.
“We recently had a student who did a case report and won first prize from the AAEP (American Association of Equine Practitioners) a couple of years ago in the student report competition. The horse in this project came here at first because it had profuse bleeding from the nose. It had a couple of repeat bleed- ing episodes, but it started at a horse show. We thought he got his mouth or nose caught on something, pulled back, and got the bloody nose,” she says.
“When he was brought to us, we discov- ered that the horse had a strange lesion in his nose. Once that was resolved, the horse started to shake its head with violent headshaking episodes. We ended up doing a CT scan and found it had a TMJ (temporomandibular joint) problem with joint damage. We injected that joint and then the horse was fine and had no more headshaking. The reason we did the CT scan was because we were looking for some- thing associated with the strange lesions we found when he was bleeding from the nose, and we picked up the TMJ problem with the scan. It hadn’t occurred to me to worry about TMJ with headshakers. I would have assumed that a TMJ problem would manifest more with dysphagia, fighting the bit, carrying the head to the side, etc.”
Wilkins reminds horse owners that headshaking is not an uncommon problem, but finding out what is wrong can be very challenging and very expensive. “We start
with the least invasive diagnostic methods first and work our way forward. It may eventually require CT scanning. A person needs to rule out several possibilities, including THO. An endoscopy can check for that going up into the guttural pouch where you could actually see the thickened stylohyoid bone,” she says.
tReatments
Some of the treatments are aimed at elimi- nating or reducing the behavior. “If sunlight is the main cause, the horse owner can use sun protection for the eyes or the horse can be kept in the dark. There are some special face masks that a horse can wear continually that provide a visor or sunglasses effect for the eyes. These horses could be kept in a dark stall during the day if they don’t have the visor on and turned out at night,” she says.
“Some of these horses that headshake
have the same problem. It seems to be sensory summation inside the brain that makes the tri- geminal nerve fire excessively. When you need to sneeze, you can sometimes stop it if you push against your nostrils, but the origin of the sneeze is in your brain, not in your nose,” she says.
There is also something called cluster tic syndrome that can cause headshaking. This
is when blood vessels in the central nervous system are next to, or associated with, the trigeminal nerve and cause these signs. This is very similar to cluster headaches in people.
“In humans, a trigeminal nerve problem can cause facial pain with nasal discharge, eye tearing, sneezing, etc. There may be seasonal- ity with periods of remission at first. A lot of horses that are headshakers may start season- ally, but eventually have the problem year- round,” says Wilkins. Horse owners may think the problem is due to allergies because of the seasonality in the beginning.
Some horses only do headshaking while being ridden, and this can be a challenge. “In these situations, I recommend people try face masks, which also act like sunglasses, or try a nose net or both while riding the horse. The face masks and ear nets that are popular today can help block sunlight and wind. Some horses don’t like wind and do more headshaking if
it’s a windy day or if there is a fan blowing on them in the barn,” she says.
“Some people tie little dangling pom-poms to the noseband when riding. These bounce around and can sometimes distract the horse from the bothersome sensation in the nose. Some people have had good luck with those, but most of these tricks only work for a while and don’t last forever.”
Diagnostics to Rule out otheR PRoblems
There are other causes of headshaking that may be due to things like ear infections or other physical problems.
“This is the reason why a horse needs a complete physical examination to make sure there is nothing going on in his eyes, such
as floaters or iris cysts bouncing in and out
of his visual plane. We also need to make
sure there is nothing wrong in the mouth
or ears. I usually do endoscopy of the upper airway and guttural pouches to see if there is a problem, since headshaking can occur early in the history of horses that develop something called temporohyoid osteoarthropathy (THO, a disorder of the voice box and associate structures). When we diagnose a horse with THO, we often find that the horse has been a headshaker or has recently started headshak- ing,” says Wilkins.
“It is always a good idea to take skull radiographs to rule out anything odd, such as a foreign body up the nose that isn’t visualized
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equine health