17 / 24
SUMMER 2015 ISSUE
NEUROLOGI CAL D I SEASE
EQUINE MATTERS
16
Causes of neurological disease
Congenital/developmental:
Cervical Vertebral Malformation, includingWobblers Syndrome;
Hydrocephalus;
Cerebellar Abiotrophy
Vascular:
Post-anaesthetic Myelopathy
Inflammatory:
Cauda Equina Syndrome/Polyneuritis equi
Infectious:
Equine Herpes Virus (EHV-1); Equine Protozoal Myeloencephalitis (EPM);
Rabies; other viral encephalitides (WNV,WEE, EEE,VEE); bacterial
meningitis/meningoencephalitis
Tumours:
Pituitary adenoma, Lymphosarcoma, Cholesteatoma
Toxins:
Tetanus; Botulism; Equine Grass Sickness; Organophosphates; Lead;
Arsenic; Russia knapweed;Yellow star thistle;Australian Stringhalt;
Rye Grass Staggers; Ivermectin/Moxidectin
Deficiencies:
Equine Motor Neurone Disease; Equine Degenerative
Myeloencephalopathy (Vitamin E)
Idiopathic:
Shivers; Stringhalt;Trigeminal neuralgia (Idiopathic Headshaking Syndrome);
Laryngeal Hemiplegia (Roaring) (Figure 2); Benign Epilepsy; Narcolepsy
Degenerative:
Equine Motor Neurone Disease; Equine Degenerative Myeloencephalopathy
Trauma:
Skull/vertebral fracture; pressure or impact of a nerve
Metabolic:
Perinatal Asphyxia Syndrome; Hepatic Encephalopathy; Hypoglycaemia;
Hypocalcaemia, Hypomagnesemia
Figure 2:
Recurrent laryngeal neuropathy
As there are a large number of
causes this article focuses on
three common diseases
Wobblers syndrome (CVM)
As horses grow, malformations of the neck
vertebrae may develop, narrowing the spinal
column causing spinal cord damage. Pinching
of the cord may be constant, or may only
occur when the neck position changes.
Thoroughbreds are commonly affected,
although any horse can suffer from CVM.
Signs can appear suddenly or gradually.
Horses appear weak and uncoordinated on
their hind legs, but some cases affect the front
legs as well.
Neck x-rays may identify bony impingement,
but a myelogram may be required to see
the pinched spinal cord. Surgery may be
possible to widen the space around the
spinal cord, but is not without risk. Many
horses are retired as they become unsafe to
ride. CVM cannot be prevented, but providing
a balanced diet to control growth rates in
youngstock is important.
Equine herpes virus (EHV)
There are a number of herpes viruses, the
EHV type 1 is most commonly associated with
neurological disease. EHV-1 generally causes
‘flu-like signs and abortions; however,
occasionally the virus affects blood vessels
in the nervous system causing neurological
disease. Horses with the neurological form
of the disease may not show respiratory
signs, but have poor coordination, hindlimb
weakness and are unwilling or unable to rise.
Nasal swabs and blood samples will help
identify EHV-1, but treatment revolves around
supportive nursing care. Excellent biosecurity
measures are needed to minimise the spread
of infection and the affected horses must be
isolated. Horses that remain standing usually
recover; however, recumbency is associated
with high fatality rates. Vaccinations do not
prevent neurological disease, but vaccinating
is still worthwhile to reduce the risk of
contracting other forms of the disease.
Trauma
Injuries to the spine or skull can cause severe,
life-threatening neurological damage. Typically
injury occurs from a collision with a solid
object; pulling back when tied-up, rearing up
and over backwards or hitting a fence are
common situations.
Signs may be immediate, including loss of
consciousness, blindness or even death; or
may be gradual, e.g. pressure from bleeding
inside the skull. Signs the horse shows will
depend on the location of the injury: neck
pain, difficulty rising, seizures are examples.
It is likely x-rays will be taken of the head
and neck; however the diagnosis may be
made from the signs exhibited. Usually
treatment involves aggressive anti-inflammatory
medication and rest. Every injury is different
and outcome varies with severity. Trauma is
usually accidental and, therefore, hard to
prevent. Making sure your horse is fit enough
for the activity you are doing is important,
and always make sure the horse can
safely break free if tied up.