Horner’s Syndrome in Dogs
What is Horner's syndrome?
Horner's syndrome is a common neurological disorder of the eye and facial muscles. The condition usually occurs suddenly. The most common clinical signs of Horner's syndrome are:
- Drooping of the eyelids on the affected side (ptosis)
- The pupil of the affected eye will be constricted (miosis)
- The affected eye often appears sunken (enophthalmos)
- The third eyelid of the affected eye may appear red and raised (prolapse of the third eyelid, conjunctival hyperemia)
What causes Horner's syndrome?
"Horner's syndrome is due to a dysfunction of the sympathetic nerves of the eyes and surrounding facial muscles."
Horner's syndrome is due to a dysfunction of the sympathetic nerves of the eyes and surrounding facial muscles. This is part of the autonomic nervous system, which helps to control normal functions such as blinking, muscle tone, etc.
"Horner's syndrome is often classified as idiopathic, which means it is without known cause."
There are many reasons for Horner's Syndrome. The dysfunction may be caused by damage to the sympathetic pathway as it runs through the neck or chest. This may be due to an injury such as a bite wound or blunt trauma, a tumor or intervertebral disc disease. Middle or inner ear disease (otitis media or interna) can also cause Horner's Syndrome. Other causes for an elevated or protruding third eyelid gland include: tetanus, facial nerve paralysis, Haw's Syndrome, facial muscle atrophy, and dehydration. However, Horner's syndrome is often classified as idiopathic, which means it is without known cause.
The onset of Horner's syndrome can be sudden and without warning. In some cases, the dog may have eye symptoms as well as excessive salivation and/or difficulty eating on the affected side
Does it affect any particular breed or age of dog?
Any dog can develop Horner's Syndrome although Golden retrievers and Cocker Spaniels have a somewhat higher incidence.
What is the treatment?
Most cases of Horner's Syndrome will resolve spontaneously. It is important to treat any underlying disease. There are several diagnostic tests that will be performed to determine if there is an underlying cause in your pet. Symptomatic treatment may include phenylephrine drops placed in the affected eye every 12-24 hours.
What is the recovery rate?
If the lesion is not due to any pathological cause, a slow recovery lasting up to several weeks can be expected.
What is the outlook?
Very good, if there is no underlying pathological cause present. The condition tends to be self-resolving but may take weeks or months depending on the severity.
Learn More about Horner's Syndrome in Dogs
To learn more about Horner's syndrome from one of our knowledgeable veterinarians, please feel free to make an appointment at a VCA Animal Hospital near you. If you are not yet a VCA client, please feel free to download our Free Initial Pet Health Exam coupon to visit with a VCA veterinarian free of charge.