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NEUROLOGI CAL D I SEASE
Veterinary surgeon
Imogen Burrows
XLEquine practice
Cliffe Veterinary
Group
Equine
neurological
disease
15
EQUINE MATTERS
What does neurological
disease look like?
The nervous system controls how the body
works; managing communication between
body parts to co-ordinate both voluntary, e.g.
movement, and involuntary actions, e.g.
breathing. Neurological diseases can have a
vast array of presentations depending on the
location and number of nerves affected.
Disorders can affect individual nerves resulting
in very specific signs, e.g. unilateral facial
nerve paralysis causing a droopy face on one
side
(Figure 1)
; or can be very widespread so
the whole body is affected, e.g. equine motor
neurone disease (EMND).
Gait abnormalities are commonly associated
with neurological disease, which arise from
ataxia and weakness. Horses sway or
stumble, looking wobbly or drunk when
walking. Owners commonly notice their horse
‘makes mistakes’; for example, tripping on
known steps, standing on themselves, making
odd over-exaggerated strides.
Other signs of neurological disease can
include altered behaviour, aimless wandering
or persistent circling, head pressing, muscle
wasting, difficulty eating, flaccid tail, facial
twitching, seizures and collapse.
Figure 1:
Horse with left sided facial nerve
paralysis showing drooping of the left side of
the muzzle.
Imogen Burrows BVetMed CertAVP(EM) MRCVS,
Cliffe Veterinary Group
How is neurological disease
diagnosed?
Diagnosing neurological disease can be
challenging and many signs are subtle and
can mimic other conditions. For example, it
can be very tricky to separate an ataxic horse
from a lame one, and of course it may be
both ataxic and lame! This means it is very
important to approach the neurological case
in a step-wise manner.
Step one: clinical history
Taking a history is critical. What signs have
been noticed and when did they start
?
Is there
history of a recent fall or accident
?
Other
information such as breed, age and use of
the horse is important as this may make some
disorders more likely than others.
Step two: physical examination
Neurological deficits may arise from diseases
affecting other body systems. Infections may
cause other signs such as raised temperature;
altered range of motion may indicate trauma;
and presence of muscle wastage and/or
asymmetry may suggest the problem has been
going on a while.
Step three: neurological examination
The aim is to identify which areas of the
nervous system are affected (localise the
lesion). By pinpointing where the problem is,
we can draw up a list of likely causes. This
examination includes observation of the horse;
testing specific nerve pathways using reflexes
and responses; as well as gait assessment,
using additional stimulation techniques, e.g.
uneven or sloping surfaces, blindfolding and
tail pulls.
Step four: further diagnostic investigation
Once we have a list of possible causes,
appropriate diagnostic testing is undertaken to
rule out or confirm possible causes, hopefully
diagnosing the underlying cause.
What causes neurological
disease?
Many disorders can disrupt nerve pathways
and their signals, causing neurological
disease. Most of these will be primary
neurological conditions, i.e. affect the
neurological system directly; but some
neurological diseases may be secondary to
another problem. For example, severe liver
disease can lead to high blood ammonia
levels, which affect the brain, resulting in
hepatic encephalopathy.