Researchers in Britain have received a grant to further investigate headshaking in horses.
Headshaking syndrome involves a horse shaking or jerking its head uncontrollably for no apparent reason.
There are striking clinical similarities between facial pain syndromes in people – most notably trigeminal neuralgia – and headshaking in horses.
Although some progress has been made towards both diagnosing and treating the condition in horses, the pathology of the disease remains unknown and further research is needed.
A recent study, led by academics from the University of Bristol’s School of Veterinary Sciences and the University of Liverpool, evaluated the long-term success rate of a pioneering new surgical procedure, called caudal compression of the infraorbital nerve.
The procedure involves the placement of platinum coils into the nerve ends within the nerve canal to relieve the pain.
The study found the surgery could be a viable option for headshaking in horses, with a long-term success rate of nearly 50 per cent.
Nonetheless, researchers are continually working to find a more effective treatment method for headshaking.
Veronica Roberts, clinical fellow in equine medicine in the University’s School of Veterinary Sciences, who led the study, has received a grant from the British Neuropathological Society to investigate possible focal demyelination of the nerve as a cause of headshaking in horses.
A demyelinating disease is any disease of the nervous system in which the myelin sheath of neurons is damaged. This impairs the conduction of signals in the affected nerves, causing impairment in sensation, movement, cognition, or other functions, depending on the nerves involved.
The term describes the effect of the disease, rather than its cause. Some demyelinating diseases are caused by genetics, some by infectious agents, some by autoimmune reactions, and some by unknown factors.
The reason the Bristol research team is looking for demyelination is that it is the most common cause of trigeminal neuralgia in people.
The team will collaborate with Seth Love, Professor of Neuropathology in the School of Clinical Sciences, as he has carried out work in this area in people.
To find a more effective treatment and to understand the disease, Roberts is requesting that anyone who is considering euthanising a horse due to headshaking to contact her for possible inclusion in her study.
A study published in Equine Veterinary Journal evaluated the long-term success rate of the surgical techniques using the platinum coils. The researchers reviewed clinical records of 58 horses that underwent the surgery between June 2004 and January 2011.
The horses, aged one to 17 years, were used for general riding, show jumping, eventing, or dressage and had a history of headshaking.
The study found:
- Surgery was initially considered a success in 35 of 57 (63 per cent) horses, but headshaking recurred between nine and 30 months later in nine horses;
- The research team repeated the surgery in ten horses;
- The overall success rate at an average follow-up time of 18 months, considering only the response to the last surgery performed, was 49 per cent;
- Owners reported nose rubbing in 30 horses at long-term follow-up after surgery;
- Nose rubbing resolved in all but four horses that were later euthanized.
Roberts said: “There are striking clinical similarities between facial pain syndromes in people, most notably trigeminal neuralgia, and headshaking in horses.
“Headshaking in horses is a major welfare issue for horses and more research is needed on the aetiopathogenesis of this pain syndrome to improve medical and surgical therapies.
“Headshaking is a significant cause of distress for some horses and this treatment in selected cases is needed even though the failure rate is limited.”
The researchers concluded from their study that the caudal compression procedure offers the best prognosis for a successful outcome compared with other treatments for horses where the only alternative is euthanasia.
However, surgical treatment needs to be improved, with further research into the pathogenesis of the disorder.
Caudal anaesthesia of the infraorbital nerve for diagnosis of idiopathic headshaking and caudal compression of the infraorbital nerve for its treatment, in 58 horses, V. L. H. Roberts, J. D. Perkins, E. Skärlina, D. A. Gorvy, W. H. Tremaine, A. Williams, S. A. McKane, I. White and D. C. Knottenbelt, Equine Veterinary Journal, September 2012, Volume 44, Issue 5.