Horner’s Syndrome in Dogs and Cats
Horner’s syndrome is a neurological condition that affects the eye and facial muscles, usually on one side of the face. Although its appearance can be alarming, it is typically not painful. At Animal Eye Clinic, Dr. Robert M. Gwin evaluates pets with Horner’s syndrome to help pinpoint the underlying cause and guide treatment.
Request an AppointmentWhat Is Horner’s Syndrome?
Horner’s syndrome occurs when there is damage or disruption to the sympathetic nerves that supply the eye and surrounding structures. These nerves follow a long path from the brain, down the spinal cord into the chest, back up the neck, and through the middle ear to the eye, so a problem anywhere along that route can cause the condition.
Signs of Horner’s Syndrome
- A smaller pupil on the affected side (miosis)
- A drooping upper eyelid (ptosis)
- A sunken-appearing eye (enophthalmos)
- A raised or protruding third eyelid
Common Causes
In many dogs, particularly Golden Retrievers and Cocker Spaniels, no specific cause is found, which is called idiopathic Horner’s syndrome. Other causes include middle or inner ear infections, injury to the head, neck, or chest, bite wounds, intervertebral disc disease, and less commonly, tumors in the chest, neck, or brain. In cats, middle ear disease is a frequent cause.
Diagnosis and Treatment
Dr. Gwin performs a complete ophthalmic and neurologic eye evaluation to confirm Horner’s syndrome and rule out other conditions that affect pupil size, such as uveitis or glaucoma. Pharmacologic testing with special eye drops can help localize where along the nerve pathway the problem lies. Depending on the findings, your primary veterinarian may recommend additional tests such as an ear exam, X-rays, or advanced imaging.
Treatment focuses on the underlying cause, such as treating an ear infection. Idiopathic Horner’s syndrome often resolves on its own over several weeks to a few months. Horner’s syndrome itself does not usually affect vision, and eye drops may be used temporarily to reduce the raised third eyelid if it is bothersome. Explore other ophthalmic diseases we treat.
Horner’s Syndrome FAQs
Is Horner’s syndrome painful?
Horner’s syndrome itself is usually not painful, although the underlying cause, such as an ear infection, may be.
What causes Horner’s syndrome in dogs?
It can be caused by ear infections, trauma, disc disease, or tumors, but in many dogs, especially Golden Retrievers, no cause is found.
Will Horner’s syndrome affect my pet’s vision?
It usually does not affect vision, though the raised third eyelid may partially cover the eye.
Does Horner’s syndrome go away?
Idiopathic cases often resolve on their own within several weeks to a few months. Other cases improve once the underlying cause is treated.
How is Horner’s syndrome diagnosed?
Diagnosis includes a complete eye exam and may involve pharmacologic testing with eye drops to help locate the nerve problem.
Can cats get Horner’s syndrome?
Yes. In cats, middle ear disease is a common cause.
Have Your Pet’s Eye Changes Evaluated
Call (918) 632-0508 (Tulsa) or (405) 751-3821 (Oklahoma City) to schedule an exam with Dr. Gwin.