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Horner’s Syndrome in Dogs… What is it? And do I need to fix it?

Horner’s syndrome is of those medical conditions that your “average Joe” probably isn’t going to know all that much about simply because it’s a pretty rare condition.

Which is…

A bit ironic because, one of the main causes of Horner’s syndrome in dog’s is the “banging” of the head or neck trauma, and as we all know, there are a lot of different types of dogs out there that have a tendency to bump their heads (says the proud owner of a little black Pug!)

But just because…

Horner’s syndrome is a relatively rare disease, this doesn’t change the fact that if your dog has been diagnosed with this condition, knowing more about it is going to be a number one priority for you.  This is why we decided to include Horner’s syndrome in our list of common ailments that can inflict our pets so that if you do have an animal that has been diagnosed with Horner’s you might have a better idea what’s to come after reading this article.

So, without further ado, let’s dive right in!

Horner’s syndrome defined.

Horner’s Syndrome is a medical condition that arises when the dog suffers damage to a group of nerves often referred to as the sympathetic trunk. This area relates to the spinal cord and chest and affects the sympathetic nervous system around the face and neck, leading to lax muscles and the appearance of drooping.

What makes this condition…

So terrifying is that it can strike any dog at any time and all it takes is a bad bump on the head. And when it does, what you’re going to find is that it will affect the eye on one side of your dog’s face.

Causing your dog’s…

Face to appear as if he suddenly lacks control of the movement there. This condition is classified as a syndrome because it summarises a selection of symptoms that are commonly observed simultaneously. In this case the syndrome encapsulates a list of symptoms that focus around the eye and brain area.

It should also be noted that…

Horner’s Syndrome is sometimes congenital (or hereditary) but it can just as easily be caused by a seemingly harmless knock on the head that does unknown damage to the spinal cord. Disease can also trigger this syndrome (such as a middle ear infection), but the syndrome itself can be symptomatic of certain diseases (such as a cancerous tumour). It can also be triggered by a lesion or a bite wound around the carotid artery which infects the sympathetic pathway adversely.


Because there are so many possible causes of this disease, there really isn’t any way for an individual to prevent this from happening to their dog, so when it does, it’s basically just “bad luck”!


Because the symptoms associated with this syndrome can vary and may not present themselves all at once, your vet may have a difficult time diagnosing the syndrome at first which can delay the implementation of a proper treatment plan right away.

This is why…

If you suspect that your dog may have Horner’s syndrome, you’re definitely going to want to take you do to the vet, but also be sure to make note of any symptoms that you yourself observe.  This way, you can provide your veterinarian with as much information as possible.

Possible symptoms you may see may include:

  • Ptosis (drooping of the upper eyelid) in one eye.
  • Anhidrosis (lack of sweating – remember that a dog’s sweat glands are on his tongue, so if you have noticed that he isn’t panting even in high heat it is possibly a symptom).
  • The pupil will not dilate quickly in response to light (also known as a ‘constricted pupil’ or ‘Miosis’ in severe cases).
  • The eyeball may appear to have sunken back into the skull.
  • The ear on that side of your pup’s head will feel warmer than usual, this symptom might appear in the nose as well.
  • You might notice that the eye in question has more visible blood vessels than usual.

The diagnosis of Horner’s Syndrome is only made when all of the above symptoms are in evidence.

The good news is…

That the syndrome itself is often not painful to the dog and sometimes your vet may decide not to do anything further than see your pet and, via otoscopic examination, make a diagnosis.

Breeds known to be affected by this condition:

Golden Retrievers are specifically at risk. They are the breed most likely to suffer from the congenital variant of the disease.

Aside from them, any other dog can be diagnosed with Horner’s Syndrome. This is because of the many ways in which it can be triggered. Bumps on the head and bite wounds are as random as can be – and we can’t wrap them in bubble wrap forever!

Treatment Options for Horner’s Syndrome

Since this is not usually a condition that causes the dog any amount of pain, the vet may choose not to treat it at all. In most cases they will still prescribe regular courses of eye drops to stop the eyes becoming itchy or sore. They may wish to undergo more tests (X-rays and MRI scans mainly) to ascertain exactly which part of the sympathetic nervous system is injured and to assure themselves that the dog has no other underlying conditions.

But be warned…

These additional tests can get pricey… your vet may want to pinpoint the specific area of the nervous system that is afflicted in order to make sure nothing else is going on. They will also want to undergo testing for various other diseases for which this combination of symptoms that are frequently associated with Horner’s syndrome.

Were we like to remind folks that we here at IndulgeYourPet are not doctors, veterinarians or medical professionals.  All we are is a bunch of folks who just happen to be passionate about animals and only want what’s best for them.

This is why…

If you feel like your pet may have Horner’s syndrome (or any other health issue for that matter) the first thing that you’re going to want to do is have him or her check out by a vet ASAP!


The truth is, an early diagnosis will often lead to the “best” medical outcome for your pet regardless of what is bothering him or her, but beyond that diagnosing a medical condition early could save you a bundle in medical costs!

This is why…

We here at IndulgeYourPet also recommend that any new pet owner take a moment and see what it might cost for you to purchase a pet insurance policy for your new animal.

Now will a pet insurance policy be right for everyone?

No, probably not.  But until you fully understand what these policies “will” and “won’t” cover and how much these pet insurance policies cost, how will you know if one might be right for you?

For more information on who we feel currently offers the “best” pet insurance policies out there, we would encourage you to check out our Best Pet Insurance Policies article.

{ 2 comments… add one }
  • Karen B-J February 5, 2020, 1:05 pm

    We live in France and my beloved golden retriever appears to have Horner Syndrome possibly caused by Lyme’s he contacted 2 years ago or even being interbred ( sadly puppy farm ). Get has diagnosed and on anti inflamatories for now. Please advise if insurance is available to us. Thank you

    • indulgeyourpet February 5, 2020, 1:22 pm


      We’re sorry to hear about the issues your loved one is having and would like to provide you with the answers you’re looking for however, because we are dealing with an already diagnosed pre-existing condition and because you are currently living outside of the United States, our only advice that we can offer would be to try and reach out to each of the companies that we listed and see if one might be willing to make an exception for your pet.

      We would also suggest contacting a local veterinarian in your area and see if their might be an insurer that operates within France that might be available to you.

      Good luck,


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