Treating Horner's Syndrome in Dogs and Cats

| Modified on Jun 29, 2022

A dog or cat with Horner’s Syndrome will appear as though they have had a stroke.  The big difference between Horner’s Syndrome and a stroke is that recovery from Horner’s Syndrome will normally occur within weeks.

What is Horner’s Syndrome?

Horner’s Syndrome is a dysfunction of the sympathetic nervous system, affecting the eye and facial muscles.  The eyelid on the affected side will be droopy and there may be both excessive salivation and difficulty in eating.  The pupil of the affected eye will be smaller than normal and the third eyelid will be red and raised.  The entire eye may look sunken.   Any age or breed can develop Horner’s Syndrome, although Cocker Spaniels or Golden Retrievers are slightly more likely to develop the problem.

What Causes Horner’s Syndrome?

There are a number of possible reasons for Horner’s Syndrome, including:

  • An injury, such as a bite wound or being hit by a car;
  • A disease, such as a tumor, tetanus or intervertebral disc disease;
  • A middle or inner ear disease;
  • Paralysis or atrophy of facial nerves;
  • Dehydration.
  • However, in many cases, there is no known cause.


A dog or cat with Horner’s Syndrome is usually given eye medication because the animal may be unable to blink normally and could develop corneal ulcers, a very painful condition that should be prevented if at all possible.

Treatment for the underlying cause of Horner’s Syndrome would depend on the diagnosis of the cause (head trauma, ear infection, tumor, etc.).  The Horner’s Syndrome could resolve itself before the underlying cause is cured.  While no cause may ever be found, Horner’s Syndrome could be a signal of another problem that should be dealt with.

If your dog or cat has had Horner's Syndrome, please let us know about your experience.

General Feedback

Posted by Jane (Houston, Tx) on 03/13/2015

Under pet's ailments, Horner's Syndrome should be listed. It is often mistaken as a stroke but can very well be an ear infection and treatable.


EC: Jane, thank you for your suggestion!

Replied by Rachel
(Waxhaw NC)

We suspect our pup has this and would like to hear other stories!