Researchers have found a biological marker for trigeminal-mediated headshaking in spinal fluid, though not yet a blood test.

Trigeminal-mediated headshaking can turn a settled horse into a frantic one within moments. He flicks his head, jerks his muzzle or shakes vertically, often with snorting or rubbing at the nose. The trigeminal nerve, which carries sensation from the face, has an abnormally low firing threshold in affected horses. A breeze, sunlight, stress or light exercise can be enough to set off a reaction described as feeling like an electric shock or an unbearable tickle (UC Davis, 2021).

There is no single test for the condition, and diagnosis has relied on ruling out everything else first: ears, eyes, teeth, sinuses. A new study published in the Equine Veterinary Journal looked at whether a nerve protein called calcitonin gene-related peptide, or CGRP, could serve as a biomarker for the condition (Weber et al., 2026). A biomarker is a measurable substance in blood or other fluid that can flag a disease or condition is present, much like blood glucose signals diabetes. A reliable biomarker allows for faster, more objective diagnosis, instead of waiting for a horse to display symptoms or ruling out every other cause one by one (Weber et al., 2026).

What the study found

CGRP carries pain signals in human conditions such as migraine and facial nerve pain, and drugs that block it have brought real relief to migraine sufferers. The German-led team measured CGRP in the blood and cerebrospinal fluid, the fluid around the brain and spinal cord, of 53 horses: 30 with trigeminal-mediated headshaking, 10 with wobbler disease (a spinal cord condition), 8 with unrelated painful conditions such as colic or laminitis, and 5 healthy controls (Weber et al., 2026).

Horses with headshaking had significantly higher CGRP in their spinal fluid than horses with ordinary pain unrelated to the nerves (p=0.001). Wobbler horses had the highest levels of all, significantly higher again than the headshaking horses (p=0.011), suggesting CGRP marks nerve irritation and spinal cord compression more broadly, not headshaking specifically (Weber et al., 2026).

Unfortunately, a blood test did not reveal the same pattern. There was no significant difference in serum CGRP between headshaking horses and healthy controls, and blood levels did not correlate with spinal fluid levels at all. That rules out a simple blood test as a marker of the condition, at least for now (Weber et al., 2026).

What this means for owners

This study does not hand vets a diagnostic blood test, and it is not a treatment trial. What it does is confirm, biologically, that headshaking involves the same nerve pain pathway implicated in human facial pain and migraine. This alone provides a foundation for future research into targeted therapies, not, sadly, a cure available today (Weber et al., 2026).

Management in the meantime stays practical. Nose nets are usually the first thing tried because they’re cheap and low risk, and they help a good proportion of horses (Roberts, 2019). Around six in ten affected horses show a seasonal pattern, often worse in bright, warm conditions, which is worth bearing in mind given how strong and consistent our sunlight is here in SA (UC Davis, 2021; Roberts, 2019). A UC Davis trial found that magnesium and boron supplementation significantly reduced headshaking, especially in more severely affected horses, but discuss this with your vet before purchasing expensive supplements.

There is no cure, and response varies from horse to horse. Vets will still need to rule out other causes of facial irritation first, such as dental disease or sinus problems, before treating for trigeminal-mediated headshaking, but this marker provides some hope that testing may soon be possible.

References

• Weber L.A., Oltmanns H., Chiavaccini L., Pickles K.J., Roberts V., Kloock T., Niebuhr T. and Feige K. (2026) Calcitonin gene-related peptide concentration in cerebrospinal fluid and serum in horses affected by trigeminal-mediated headshaking. Equine Veterinary Journal, doi:10.1002/evj.70139.
• Roberts V. (2019) Trigeminal-mediated headshaking in horses: prevalence, impact, and management strategies. Veterinary Medicine: Research and Reports 10.
• University of California, Davis, Center for Equine Health (2021) Trigeminal-mediated headshaking.