Headshaking — when the head tossing is a nerve pain and not a vice

Headshaking describes an abrupt, involuntary and repetitive flinging or striking of the head — usually upward, often accompanied by snorting, wrinkling of the nose, rubbing the nose against objects or against the horse's own leg. Characteristic is that the movements shoot in suddenly, as if the horse were reacting to a sting or a tingling that no one sees. Precisely this impression leads to the core of the understanding: in many cases it is not a vice under saddle, but a real, physical stimulus.

Why the facial nerve is at the centre

A considerable part of the severe cases is today classified as trigeminal-mediated. The trigeminal nerve is the large facial nerve that controls, among other things, the sensation of the nose, mouth and face. In the trigeminal-mediated form this nerve appears to be hypersensitive and to transmit stimuli as a painful burning, tingling or stinging, although no external injury is present — a neuropathic facial pain, comparable to nerve pain in humans. This explains the sudden, seemingly groundless onset of the head movements: the horse reacts to a pain stimulus that arises in the nerve itself.

Light and season as triggers

Strikingly often, owners report a seasonal pattern: the signs begin in spring or summer and subside again in autumn, in part year after year almost on the same date. In a proportion of the horses a relation to light can additionally be observed — the so-called photic form. Here bright sunlight intensifies the symptoms, while covering the eyes, dusk or darkness can clearly ease them. It is suspected that light stimuli, via a cross-connection, also help to set off the hypersensitive facial nerve — a mechanism that resembles light-triggered sneezing in humans.

A symptom complex — and why exclusion diagnostics is indispensable

As striking as the picture is, headshaking is by no means a finished diagnosis. The same head striking can have many causes that must first be clarified: problems with the teeth or sinuses, diseases of the ears or guttural pouches, eye disorders, unsuitable equipment with pressure on the poll or on the bit, pain in the back or simply the rider's influence. Only once these sources have been systematically excluded does trigeminal-mediated headshaking remain as the classification. This is why one speaks of a symptom complex requiring exclusion diagnostics — and why the clarification belongs imperatively in veterinary hands, often with examination of mouth, eyes, ears and head as well as imaging procedures.

Reduce triggers instead of suppressing symptoms

Because the nerve cannot simply be switched off, management first aims to reduce known triggers. In light-sensitive horses, eye protection from light or avoiding glaring midday sun can help; in horses that react to stimuli at the nose, nose nets are used that give a gentle, distracting stimulus to the nostril entrance. Such measures do not cure the underlying hypersensitivity, but they do provide relief for a proportion of the horses. Which triggers play a role in an individual horse and which measure is sensible can only be assessed individually after a veterinary examination.