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HEADSHAK ING
Headshaking
Syndrome
in Horses
Jane King BVetMed MRCVS,
Westmorland Veterinary Group
Veterinary Surgeon
Jane King
XLEquine Practice
Westmorland
Veterinary Group
What do we mean by
headshaking?
Headshaking sounds such an innocuous
term but it can make the affected horse's life
a misery and render them unrideable.
Horses may shake their heads for a variety
of reasons: for example as an evasion or
to escape from pain in the mouth, back or
elsewhere. In some, it may be a response
to stress or in anticipation of food or exercise.
All of these are voluntary actions as the
horse is choosing to toss his head.
Headshaking syndrome is different; it is
an involuntary action.
There is a huge spectrum in the severity of
signs shown, from the occasional twitch to
horses who are obviously very distressed and
can become dangerous to ride or will rub the
sides of their faces so hard they will damage
themselves. The condition is thought to be akin
to trigeminal neuralgia in people (severe facial
pain). The site of the pain (muzzle and nose) is
not the source of the pain, which is within a
branch of the nerve deeper in the horses head.
The trigeminal nerve is a sensory nerve
receiving information from the head and
sending messages to the brain. In headshaking
syndrome the nerve overreacts misinterpreting
sensory stimuli as painful, hence the sudden
violent reflex action. The action may be
triggered by sunlight, rain, wind, pollen or flies.
Sunlight is a key trigger and most of the others
are also more likely to be present in the spring
and summer.
How can we diagnose
headshaking?
Your vet will take a careful history including
how long you have owned the horse, when
signs started and if there are any triggers.
They will want to perform a full clinical
examination to rule out any obvious physical
causes. If it is safe to do so, the vet may want
to see the horse ridden or exercised to see the
behaviour. The characteristics of the condition
means the vet may make the diagnosis from
his examination alone but sometimes, local
anaesthetic may be injected either around the
infraorbital nerve or further back in the head
behind the eye. The idea is to see if numbing
the nerve eases the signs; this may be done
to help decide if the horse is likely to respond
to surgery.
Is there a link to
Equine Herpesvirus?
Some researchers have suggested a link to
equine herpes virus (EHV). EHV does like to
persist in nerve tissue and has been found in
parts of the trigeminal nerve at post mortem
of headshakers. Research is ongoing in
this area.
Nose nets can reduce contact of irritants
with the nose
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EQUINE MATTERS
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sudden violent vertical downward flick
of the nose
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repetitive involuntary behaviour
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sneezing, snorting
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runny eyes, runny nose
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seasonal
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more common in geldings
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rubbing nose and muzzle on foreleg
Characteristics of headshaking
syndrome:
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some show photophobia, squinting in
bright sunlight.
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minimise triggers and avoid riding in
bright sunlight if possible;
Treatment options available:
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use a nose net, this reduces contact
of irritants with the nose but also
dampens down the nerve response by
the contact of the material with skin;
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sadly, some horses with the condition
deteriorate and may have to be put to
sleep on humane grounds or because
they become difficult to handle.
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magnesium supplements;
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pulsed steroid therapy;
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acupuncture;
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human drugs such as cyproheptadine,
tegretol and gabapentin;
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surgery is performed at specialist centres
where they insert a coil around the nerve;