This horse has facial sweating on his left side (right side as you look at it), with a small eye (enopthalmos)
Neurology is a very complex and exciting area of veterinary medicine. Today we will discuss one syndrome that is particularly interesting:
Have you heard of Horner’s Syndrome in horses before?
Horners is a ‘Syndrome’ because a group of clinical signs are consistent which characterise the condition.
Horner’s syndrome in horses is a neurological disorder (nerve disorder), that is characterised by the following;
Drooping of the upper eyelid (ptosis)
3rd Eye lid prolapse (due to sinking in of the eye)
A small pupil (miosis)
One-sided sweating of the neck, ear and face
To diagnose the syndrome, we will perform;
A complete clinical examination of the horse
A detailed opthamological (eye) examination
Endoscopic evaluation (using a long camera) of the guttural pouches
Radiography or Ultrasonography if warranted
We look for the classical presentation of the clinical signs mentioned above. As a horse owner, the most common clinical sign you will notice is the drooping of the upper eyelid. Please note here, the most common cause of what appears to be a ‘droopy eyelid’, is in fact a sore eye, where the horse is actively squinting (blepherospasm), due to a painful focus. You may also notice the appearance of the 3rd eyelid. This again most commonly would be due to a trauma or an inflammatory focus in the eye.
There are many possible causes of this syndrome, but damage to the sympathetic nervous system (fight or flight response) is common in all situations.
The most common causes of the syndrome include;
Neck trauma; fracture of bones, damage to soft tissues, or deep wounds.
Abnormalities of the guttural pouch (extension of the eustachian tube that is located under each ear inside the head)
Intra-venous injection of drugs leaking outside the vein (this can happen with incorrect technique or occasionally the drug leaking back out of the venepuncture site). The most common drugs to cause this are Vitamin E/Selenium, Xylazine (a sedative), and Phenylbutazone (bute)
More rarely spinal trauma, masses in the chest, brachial plexus trauma.
Complications seen associated with Horners Syndrome include;
Corneal ulceration from the inability to blink
Hair loss (alopecia) over the area that is sweating.
Poor performance, due to nasal oedema and reduced air flow. Occasionally laryngeal paralysis can be seen depending on the cause of the Horners Syndrome.
Following a full clinical examination, we hope to be able to provide you with an aetiology (cause) for the development of the ‘Horners Syndrome’. Once the causal factor is diagnosed, we would commence treatment. The good news is that improvement is often seen within weeks of correct treatment. The prognosis does however, depend on what is causing the syndrome.