Head shaking has been described as a syndrome for many years but is still a largely misunderstood condition.

Initially it was thought that this was a behavioural issue but further research has shown this not to be the case. There are many reasons why horses shake their heads. It can be a simple reaction to insects especially over the summer months. Other causes include resentment to the rider or bridle, ear or ocular issues. However some horses shake their heads violently and uncontrollably without external reasons being clear. Some horses will shake their heads to a point where they are too dangerous to ride or handle and euthanasia may have to be considered.

Signs that you may see include shaking their head from horizontally (side to side) or vertically (up and down). Other signs include extreme agitation, snorting, head tossing, violent shaking or jerking of the head or neck, rubbing the nose/face, nostril clamping.

 

nostril rubbing horse

Identification of the cause can be difficult. In many cases you should contact your vet to investigate the reasons for this. History is an important factor; has your horse suffered from this before, has there been any changes to management (change of stable, loss of companion, moved to a different area where oil seed rape is more prevalent). The investigation performed by your vet may include orthopaedic, neurological, opthalmological, respiratory and oral assessment. Further investigation may be needed and may include radiography, scintigraphy, endoscopy or computed tomography to help identify reasons for the head shaking.

If it is still unclear of the cause of the disease your horse may be diagnosed with 'idiopathic head shaking', in fact up to 98% of cases receive this diagnoses! Research into head shaking has shown that many of these idiopathic cases are due to facial pain from a neuropathy (nerve disease) of the trigeminal nerve, the main sensory nerve to the face. It is referred to as Head shaking Syndrome in horses and is similar to facial pain syndrome in people. It is a sensation of tingling, pricking, or unpleasant nerve pain known as trigeminal neuralgia. In horses, the condition can be triggered by over activity of the various branches of the trigeminal nerve that bring sensation to the face and muzzle. Trigeminal mediated head shaking is often sudden in onset, although gradual and usually seen between six and twelve years of age. The trigeminal nerve is sensitised, firing at too low a threshold. If your horse is believed to have this condition then the first point of diagnosis would be a nerve block (where local anaesthetic is placed into the trigeminal nerve to see if it stops the head shaking).

Multiple treatment options for idiopathic head shaking have been investigated, with various levels of success. The use of nose nets has been affective in some cases. If the cause of head shaking is due to allergy then a number of different drugs including antihistamines can be used. S

Some horses will require surgery which is a caudal compression surgery offered from some specialist centres with a success rate of around 50%. Research has been conducted into percutaneous electrical nerve stimulation (PENS neuromodulation) as another possible treatment, and is suggested as a treatment for those horses where nose nets have not worked.

Sadly trigeminal mediated head shaking still carries a poor prognosis, even with the availability of neuromodulation.

This article was written by Dr Rachel Glabocki

www.swanspoolequine.com

Veterinary advice in this magazine is provided as a general guide and you should always seek professional advice.

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