Headshaking syndromes include ailments that results in horses repeatedly and intensely tossing their heads for no apparent reason - usually up and down, but sometimes side to side or in a circle.

Headshaking can vary in severity from mild or occasional head bobbing to violent jerks involving the entire head and neck. This behavior can be triggered by outside stimulus (or not), it can occur year round or seasonally, and it may increase in severity over time.

Chronic headshaking in horses is poorly understood and causes frustration for horse owners and veterinarians. A variety of studies have failed to definitively identify the cause of this behavior and more research is needed.

Strictly speaking, headshaking is not a diagnosis but a sign of another underlying problem or disease. For the majority of horses that shake their heads, no other evidence of disease can be found. Horses in that group can be called "primary" headshakers versus those for which disease or injury in another body system can be proven, resulting in "secondary" headshaking. Idiopathic ("of unknown cause") headshaking are cases that cannot be attributed to an underlying cause with veterinary diagnostic testing.

It is important to know that headshaking behavior in RIDDEN horses often relates to training and rider problems, and less commonly to discomfort from ill-fitting tack or dental conditions.

Similarly, headshaking in horses that are not under saddle sometimes results from diseases associated with different body systems; guttural pouch problems, external and internal ear problems, sinus conditions, oral and dental conditions, and even skull and neck injuries.

We use the term "Idiopathic" when we are simply not sure why something occurs. The vast majority of horses that shake their heads abnormally fall under this category. You will see lots of names given to the syndrome, depending on its characteristics in that particular horse.

Head shaking may be triggered or worsened by bright light. This condition is often called photic head shaking. When these horses are led into bright sunlight from darker environments, head shaking starts and can be violent and persistent. The severity may vary, depending upon many factors and is graded by vets on a scale of 1-5.

Trigeminal headshaking is the term used when this behavior is thought to be caused by inflammation of the trigeminal nerve, which is responsible for skin sensation on the face. In these cases, sensory nerve irritation brought on by light, wind, cold, touch or other external factors is thought to cause a tingling or burning sensation in the facial skin. This is really difficult to separate from photic headshaking, except that not all cases of trigeminal headshaking worsen during exposure to light.

Studies suggest that this behavior could be caused by residual viral presence and inflammation following a viral infection. Others postulate that trauma or hormonal changes could be related.

DIAGNOSIS: The key to diagnosing and treating headshaking syndromes is to rule out all of the other more obvious causes of irritation that could result in this behavior. If all other possible causes are excluded we are left with idiopathic/photic/trigeminal headshaking as the diagnosis.  

TREATMENT: Treatment is focused on resolving the underlying cause. In cases where no underlying cause can be identified, there are several medications (carbamazepine and cyproheptidine) that have shown some therapeutic value in some horses. Nose nets and face masks may help in some cases of the photic syndrome and are a practical starting point. There are lots of other proposed treatments, from acupuncture and homeopathy to surgery (severing nerves that supply sensation to the muzzle and face) but none of these solutions have been shown to be universally helpful. The key is working with your vet, consulting with an expert in the field, eliminating other causes and then trying management approaches.