Nodding away flies and giving the odd head bob is normal horse behaviour, but full-blown head shaking in horses could mean something rather more serious is going on. While the number of affected horses is generally low, those who do suffer with head shaking find that it is a distressing condition.
Picture this: your horse is uncontrollably and involuntarily shaking their head in a violent fashion, jerking it up and down while also snorting and sometimes rubbing their muzzle. They seem distressed. The horse you are picturing is a head shaker.
Horses may also (although this is less common) shake their head horizontally or rotationally in a movement that’s neither behavioural nor stereotypical in nature. I don’t mean a few blows of the nose when you first start riding, or nodding their head to swot pesky flies on a summer’s day. Head shaking in horses shouldn’t be confused with head tossing.
What causes head shaking in horses?
Many questions about head shaking in horses remain unanswered, and research into it is ongoing. It’s thought that head shaking results from trigeminal nerve pain (known as trigeminal-mediated headshaking/trigeminal neuralgia) which frequently involves the branch of the trigeminal nerve supplying the nasal cavity.
Occasionally, a physical cause of the pain is identified but, more often than not, the precise cause of the pain cannot be found, meaning that the vast majority of head shaking cases are termed ‘idiopathic’ (cause unknown).
A trigger factor generally precipitates head shaking in horses and can include certain climatic conditions (bright lights, warmth, cold, wind, rain and so on), environmental allergens, insects, and other possibilities.
Diagnosing head shaking in horses
Head shaking varies in severity and can be graded on a scale of one to five. Grade one is an infrequent nasal twitch, while grade five will see an incredibly distressed patient who exhibits excessive head shaking and will be unsafe to handle, let alone ride.
There is often a seasonal link, with clinical signs starting in the spring and getting worse over the summer before abating in the winter. In some horses, though, clinical signs aren’t season-dependent. Other horses may only head shake intermittently, or under certain conditions.
Should your horse or pony start to head shake, you should seek veterinary advice and provide your vet with as much historical information as possible. They will need you to provide:
- An accurate description of the signs your horse is displaying.
- How long your horse has been displaying symptoms.
- Whether these symptoms are persistent or intermittent (ie do they come and go or are they present all the time?).
- Whether management changes or any environmental factors seem to exacerbate or alleviate symptoms (such as being in the field rather than the stable, or summer months versus winter months).
- Whether or not you’ve tried any treatments and, if so, the success rate.
Investigating head shaking in horses
Your horse will need to undergo a full physical examination, including looking at their eyes and teeth. If I am told that signs of head shaking are only evident when the horse is being exercised, I will ask to watch the horse being loose-schooled, lunged or ridden (provided it’s safe to do so). This means I can observe and grade the head shaking ‘in action’.
Further investigations may be recommended. By this I mean taking blood samples, X-raying the skull and having an upper respiratory tract endoscopy. An endoscopy (which you may heard being referred to as ‘scoping’) is where a camera is inserted into the nose to view the inside of the horse’s nasal cavities, pharynx, larynx and guttural pouches.
If these investigations prove inconclusive, nerve blocks and/or a CT scan of the horse’s head may be necessary.
If a specific source of pain is localised, such as head shaking in horses related to dental disease, then appropriate treatment will be needed that will hopefully result in the resolution of the problem.
Treating head shaking in horses
Sadly, idiopathic head shaking in horses isn’t curable. However, a number of treatments may be tried in the hope of reducing the problem. Many of these are unproven and lack sound scientific evidence, so take care if you decide to use them and seek advice from your vet. Options include the following:
- Nose nets, UV masks and ear covers may help, either individually or in combination.
- Equine-specific contact lenses can be used in cases where corneal sensitivity is considered a trigger factor. Horses who show a positive response to topical, local anaesthetic eye drops gain the most benefit from contact lenses.
- Your vet may also recommend an intranasal inhaler, especially if endoscopy has indicated inflammation of the nasal passages or upper respiratory tract.
- Oral antihistamines, steroids or non-steroidal anti-inflammatory medications (NSAIDs) can have varying degrees of success.
- Other drug options include carbamazepine and cyproheptadine, though results are variable and often short lived.
Case study: assessing a head shaker
When a 16-year-old Connemara pony I know developed fairly persistent vertical and horizontal head shaking, he had been living with the same family for three years and never shown any symptoms. In fact, he had been the perfect children’s pony with no significant medical issues.
I couldn’t link the head shaking to weather conditions, and symptoms occurred when the pony was both inside and outside. However, symptoms worsened when he was being ridden. His owners didn’t make any management modifications prior to calling me and their main concern, obviously, was their children’s safety.
I gave the pony a full physical examination, but this showed no abnormalities, and nor did an eye and dental check. The vertical and horizontal nature of the head shaking was apparent when I watched him being ridden, and I graded him as a two.
Respiratory tract endoscopy and head radiology again showed nothing. The pony’s owners were then given the option of a treatment trial or further investigations. They opted for the latter.
A CT scan showed an abnormality of the roots of a left lower cheek tooth. The sensation to the tooth was blocked and this resolved the head shaking. The tooth was subsequently extracted.
The pony no longer head shakes and he has returned to being the happy, pain-free children’s pony he was before the head shaking started.
Research into head shaking in horses
Research is ongoing into head shaking in horses. Scientific research suggests that EquiPENS (Percutaneous electrical stimulation) neuromodulation is showing promise as a minimally invasive procedure. Its aim is to reset the threshold level for nerve firing to normal and normalise the facial sensations experienced by the horse.
The procedure involves placing a probe directly over the nerve and stimulating it for a set period. Research indicates that 50% of horses treated have benefited from EquiPENS.
In idiopathic cases that have shown no signs of improvement to any of the above measures and procedures, there are two options: euthanasia or surgery. Caudal compression of the infraorbital nerve can improve clinical signs in more than 50% of cases. However, reoccurrences and post-operative complications may occur.
My best advice is that if you suddenly notice any head shaking in your horse or pony, call your vet straight away.
Main image: copyright Shutterstock; diagram: copyright Your Horse Library/Kelsey Media
