Headshaking has been well described as a syndrome for many years but is still a largely misunderstood condition. Although the condition was historically thought to be a behavioural problem, we now know that in many cases headshaking is caused by extreme pain across the face. This pain causes the horse to headshake, strike out at the face or rub the face in an attempt to gain some relief from the pain. This is a major welfare problem for affected horses, particularly if the signs are not recognised and treated appropriately.
It is still not clear what the exact cause of the disease is, and when no physical cause for the headshaking can be found, horses are diagnosed with “Idiopathic Headshaking”. Studies have found that up to 98% of horses presenting to a referral hospital for investigation of headshaking are diagnosed with Idiopathic Headshaking. When local anaesthetic is infiltrated around a branch of the trigeminal nerve (a nerve block), a majority of horses affected by Idiopathic Headshaking stop headshaking for the duration of the local anaesthetic. This proves that the headshaking is caused by facial pain. Whilst this technique would be impractical to use as a treatment for headshaking, it is used to aid diagnosis of headshaking caused by a facial pain syndrome.
The pain originates from a branch of the trigeminal nerve that runs along the face. This is the same nerve that is affected in a condition seen in humans, known as Trigeminal Neuralgia, which has many clinical similarities with Idiopathic Headshaking. Trigeminal Neuralgia is characterised by sharp, shooting pains across the face. As with headshaking, the symptoms are unable to be controlled through the use of ordinary pain killers. The pain is so severe that Trigeminal Neuralgia has been dubbed ‘the suicide disease’, owing to the high rate of suicides in patients diagnosed with the condition.
Signs that a horse may be a headshaker include:
• Repetitive upwards movements of the head
• Nostril clamping
• Pinching of the muzzle
• Striking out at the face
• Rubbing the nose / face
Because headshaking is associated with such severe pain, and is typically a progressive disease, it is advisable to contact your vet if you suspect your horse may have developed headshaking. Diagnosis of Idiopathic Headshaking is a ‘rule-out’ diagnosis and requires multiple diagnostic tests which may require referral to a specialist.
Multiple treatment options for Idiopathic Headshaking have been investigated, with varying levels of success. The use of nose nets has been found to be effective in the management of some cases.
The current treatment option offering the best chance of long term cure is caudal compression surgery. Research has found that this surgery has a 63% long term success rate, but is also associated with a significant incidence of side effects. A clinical trial is underway at Langford Veterinary Services, University of Bristol to adapt and improve the current technique.
This research was conducted by our bursary student Amy Coleman.