Headshaking

Recent research has shown that only 25% of owners with a headshaking horse sought veterinary help. In the past, it was believed that this was an evasive behaviour, and that horses were simply being badly behaved and needed a strong rider and more severe tack. But as our understanding of the condition has improved, attitudes have changed significantly among horse owners and vets. However, there’s still quite a long way to go.

What is headshaking? 

One reason for the huge amount of misunderstanding is that the term headshaking simply refers to the visible clinical sign – the fact the horse is shaking his head – and not the underlying cause of the problem. 

It can be caused by any number of things, but it’s usually pain or irritation that causes the horse to throw his head around. Pinpointing the underlying cause is tricky, though, but it’s important to find the cause so the condition can be successfully treated and managed.   

Noticing patterns

Identifying a pattern can help your vet find the underlying source of the pain.

When your horse shakes his head, does it happen… 

• all the time?
• only when ridden? 
• only when being schooled?
• only when cantering?
• only in some seasons of the year?
• only when in certain fields or paddocks?
• only when eating?
• completely randomly, not associated with any activity or location?

And when he shakes his head…

• does he flick his head up and down or round in circles? 
• is his head tipped to one side? 
• is it worse on one rein than the other?
• does he appear to be distressed? 
• are there any other signs of pain?

It’s also worth considering whether…

• he’s comfortable being tacked up
• he’s performing well otherwise 
• he drops food when he eats 
• he reacts abnormally when you touch any part of his head 
• the shape of his head has changed 
• he has nasal discharge and, if so, whether it’s coming from one or both nostrils

Common causes

Diseases that can cause headshaking include…

dental disease Fractured teeth, cavities, mouth ulcers or other trauma in the mouth can cause pain. They can also cause your horse to drop food when he’s chewing 

pain from other areas of the body This can cause horses to headshake simply as a manifestation of distress or pain. It’s most commonly caused by orthopaedic pain, such as back pain or even neck pain

nerve pain (trigeminal-mediated headshaking) This is recognised in humans as trigeminal neuralgia and causes the classic headshaking signs we see in horses. Humans with this condition report that it’s extremely painful and distressing, and we suspect that the same is true for horses. The trigeminal nerve runs from the brain, through the sinuses at the front of the head and pops out of the skull about halfway down each cheek. 

In cases of trigeminal neuralgia, the nerve responds to small stimuli that wouldn’t normally cause the nerve to fire. This means that the horse feels pain in response to a tiny, normal stimulus that wouldn’t normally cause any problems. These triggers are thought to include pollens in the air or, in some cases, light. This results in a sudden, severe, shock-like pain on one side of the face, which can last from a few seconds to a few minutes

sinusitis The sinuses are air-filled cavities at the front of the head. If there’s a problem in the sinus, such as a mass or accumulation of pus, then this can irritate the trigeminal nerve, causing pain and headshaking

Under investigation

First, your vet will examine your horse to rule out problems such as obvious dental disease or lameness. Tell them if you have recognised any activities or triggers that cause the headshaking, and how long it’s been going on for, as it will help them in their investigation. 

If your vet is unable to identify a cause, your horse will be referred to see a specialist. It is likely that the specialist will… 

• watch your horse being lunged and ridden
• look in his eyes 
• examine his airway and guttural pouches with an endoscope
• check his teeth 
• perform nerve blocks on his head 
• carry out a CT scan to look for subtle abnormalities in his teeth and the bones in his head 

If at the end of the examination no abnormalities have been found and all other possible causes have been ruled out, your horse will be diagnosed with trigeminal-mediated headshaking.

Tackling the problem

If the investigation identifies a cause, such as dental disease or sinusitis, then once the problem is treated, the headshaking should resolve. 

For horses with trigeminal-mediated headshaking, the first line of treatment is a nose net. If this doesn’t improve the signs, then EquiPENS neuromodulation is recommended. This is currently the safest and most effective method of managing trigeminal-mediated headshaking in horses who don’t respond to a nose net.

EquiPENS appears to stop the nerve responding to inappropriate stimuli such as pollen or light, and returns it to normal function. The treatment involves inserting an electrode into the trigeminal nerve on the top of your horse’s nose under sedation and it’s generally very well tolerated by patients.

Several treatments are given a few days or weeks apart. After this time, some horses are completely better and some require further treatment every few weeks or months, but in some horses there’s no change. If EquiPENS is ineffective, the specialist may recommend certain medications that alter nerve function. There are currently no surgical options for treating headshaking. 

Ongoing research

Extensive research at the University of Bristol is continuing to further improve the treatment of equine headshaking. Hopefully, with a better understanding of this debilitating condition, we’ll be able to develop more effective treatments.