Why is my horse shaking his head?

Sinus problems can be another culprit, and sometimes because of a tooth root problem such as infection or abscessation. Depending on the results of his dental examination, your horse might need some X-rays taken to get a better look at the sinuses. It could even be that your horse’s headshaking reflects the discomfort it feels having inhaled some foreign material up into the nasal passages.

Next up, guttural pouch disease. 

Guttural pouch mycosis involves fungal infection of this hidden-away structure. These horses might have other signs like discharge or bleeding from the nose. A camera (endoscope) is used to examine it for any sign of infection and take samples if needed. 

Or a behavioural or pain-related problem

It might be that headshaking is the horse’s way of defying its rider. Or perhaps an escape route for the weaker horse, trying to evade doing work that it finds physically challenging. Equally, musculoskeletal problems of the head, neck and back may also manifest through headshaking. This means that further x-rays or other imaging modalities might be needed in the veterinary work-up. 

“Trigeminal Headshaking”

There are some horses where investigations come up with no obvious reason behind their headshaking. We are becoming more aware of idiopathic headshaking or idiopathic trigeminal-mediated headshaking. This is headshaking of an unknown cause, suspected to result from the sensation of pain in the face.

In idiopathic headshaking, it seems like the nerve supplying sensation to the face isn’t working properly. As well as headshaking, these horses might rub at their faces and snort and it’s often worse when the horse is being ridden. The condition is suspected in horses where another underlying cause cannot be found,