headshaking syndrom

Equine Headshaking Syndrome can be extremely painful and debilitating. Here are some things you should know, and how to help your horse.

All horses shake their heads from time to time, usually as a reaction to insects or other irritating stimuli. If your horse begins to headshaking more than normal, there may be a medical or mechanical reason for it. Medical causes can include middle ear disorders, ear mites, cranial nerve disorders, guttural pouch infection, or head trauma. Mechanical causes could encompass poorly-fitting tack, sharp teeth, or rough hands during riding. If your horse is shaking his head excessively, eliminate all these possibilities first.

Headshaking Syndrome

Also called photosensitive headshaking, Equine Headshaking Syndrome is a condition in which a horse flips his head in reaction to sunlight, wind, movement, stress, etc. He may display only mild annoyance – or he may exhibit sheer panic and extreme pain. Some head-shakers will hit their heads against walls because of the deep pain in their heads. Some will strike at their noses with their forelegs because of the biting or burning sensation. Others may simply scratch their noses on everything they can find.

This behavior can also include extreme nose blowing, snorting and coughing. The horse may exhibit signs of photophobia, or he may not. He may put his nose under another horse’s tail or dunk his nose in his water bucket. Some horses may refuse to move forward and will rear if forced. Owners should be aware that horses with headshaking syndrome may be suffering terribly and should not be forced to work in pain. Headshaking Syndrome is painful and debilitating and should be treated as you would treat any serious illness.

The brain-body connection 

Trigeminal neuralgia is a human condition described as an intense nerve disorder that causes a stabbing or electric shock-like pain in parts of the face. Nicknamed “the suicide disease”, it is a disorder that is painful and confounding to many. Treatments for humans include several drugs that are mood-altering or mood-stabilizing. Phantom limb pain is a human condition that is described as pain felt in a limb or organ that was previously amputated. Most often the sensation from the body part that has been amputated is painful. However, in most instances the patients report that they also “feel” the body part moving as it would have had it not been taken off. Both of these conditions are similar to Equine Headshaking.

In the late 1970s and early 1980s, Michael Merzenich, Jon Kaas and Doug Rasmusson found that by using cortical maps they were able to determine which parts of the brain were activated by certain parts of the body. What they also found was that when a part of the body was amputated, its cortical map changed.

All pain is perceived in the brain. This is where the sensory cortex registers external sensory information. When a portion of the brain that has previously been assigned to a body part is no longer receiving information from that body part, it is soon occupied by the sensory information from another body part. But the brain doesn’t know which part is sending the signals. So your consciousness still identifies the previous part as the sender. Often when upper limbs (forelimbs) are amputated in people, sensory portions of the brain are taken over by portions of the face. In humans who were born with eyesight but lose it later in life, the sensory portion of the brain that once was stimulated by their eyes is often taken over by their finger tips, and they begin to “see” with their fingers.

Mixed signals

Since amputation of organs can also cause this sensation, it is plausible to say that rewiring of the brain can go on even when there is no amputation. Pain from organ systems which are not often localized to the organ but to an external body part, such as numbness or pain in the front limbs during a heart attack illustrate this situation. Head shakers or fly-flicker-syndrome in horses can be likened to trigeminal neuralgia. It is often treated by applying a light mask to the nose of the horse, which sends a counter sensory signal to the brain and quiets the initiating stimulation (we call this inhibition in relation to the brain and spinal cord). However, it doesn’t address where the sensory signal is originating. Similar to phantom limb pain and trigeminal neuralgia, head shakers are likely responding to sensory signals coming from other areas of the body. This could be organs that are irritated, in a similar manner to a heart attack. If this is the case, consider gastro-intestinal involvement since the GI tract in the horse sends many signals to the brain regarding sensory information. It could be as simple as sensory input from an amputated organ, such as in the case of removing the testicles from a stallion.

Common triggers and possible solutions

The New Bolton Lecture series reports headshaking is usually an adult-onset disease, starting at around seven to nine years old. Geldings are most commonly affected, and horses that are over-conditioned seem at higher risk. Horses can be seasonal head-shakers or shake all year round, and some will progress from seasonal to year-round. Common triggers for headshaking are bright light, heat, spring/summer season, and exercise. These commonalities suggest that the actual cause of the stimulus to the horse’s face is coming from a distant sensory pathway which moved in on the face portion of the brain. Horses in heavy work are usually on high carbohydrate diets which change the lining of the GI tract, causing sensory input from this tract to change. Ulcers reported in these horses confirm this.

Bright light causes constriction of the muscles of the eye, which fire into the area of the brain nearest the extensor muscles of the horse. Turning on these muscles can trigger pain muscles already in spasm through other neural channels linked to the GI tract.

Trigeminal neuralgia can be caused by trauma or tumors, however, its cause often remains undiscovered. Similar to head shakers, it occurs in older humans, usually over 50, though it occurs more commonly in females. In humans, the nerves of the face often lose their coating to become pure pain fibers. This may be similar in chronic horse cases.

Altering your horse’s diet and helping remap his brain are two ways to address this issue. Reducing processed food and carbohydrates in the diet will greatly reduce the inflammatory proteins in the body. Ways to begin remapping the brain include chiropractic adjustment because it realigns the sensory input to the face, and the rest of the horse. Acupuncture therapy has been shown to help as it also helps to rewire pathways, and homeopathic remedies can aid the organ from which the pain originates.

While more research is needed to locate the origins of headshaking, resolving the issue in your horse is more important. The therapies mentioned above typically offer some relief, which is often well received by both the owner and the horse.


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