New Research on Headshaking in Horses

Headshaking in horses is a frustrating and potentially dangerous syndrome.

“Potential causes for headshaking are varied, though many can be improved once a veterinarian identifies the underlying cause,” explained Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research.

Such examples include, but are not limited to, stereotypic behavior; ear infection, including mite infestation; dental pain; temporomandibular joint disease; ill-fitting equipment; and eye pain.

Another condition—trigeminal-mediated headshaking—can also induce intense and violent shaking, predominantly in a vertical direction.

According to veterinarians from the School of Veterinary Medicine, University of California, Davis,* trigeminal-mediated headshaking occurs due to misfiring of the trigeminal nerve.

As described by Sheldon and coworkers, trigeminal-mediated headshaking induces “episodic intractable facial pain, compromised performance and quality of life, and ultimately leading to euthanasia of severely affected horses, thus representing a major welfare concern.”

Other signs associated with this condition include apparent itchiness, tingling, and presumed burning or electric-like sensation in the horse’s face. Affected horses may also snort, rub their muzzle on their limbs, or strike at their face.

Treatment is reliant on the underlying cause. In cases of trigeminal-mediated headshaking, Sheldon and colleagues reported that intravenous administration of magnesium sulfate could help.

“Magnesium is an invaluable micronutrient, participating in hundreds of biochemical reactions in the horse’s body. It also plays an integral role in the transmission of nerve impulses, and could even provide neuroprotective effects,” relayed Crandell.

In the aforementioned study, six geldings diagnosed with trigeminal-mediated headshaking were treated with either an intravenous 5% dextrose (sugar) solution or intravenous magnesium sulfate (50% solution dosed at 40 mg/kg body weight).

Horses treated with magnesium sulfate had measurable increases in blood levels of magnesium, and the treated horses had a 29% reduction in headshaking rate.

To ensure your horse’s diet is appropriately balanced, consult a Kentucky Equine Research nutrition advisor today.

*Sheldon, S.A., M. Aleman, L.R.R. Costa, et al. Intravenous infusion of magnesium sulfate and its effect on horses with trigeminal-mediated headshaking. Journal of Veterinary Internal Medicine. In press.