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Horner's Syndrome in Cats: Causes, Symptoms & Treatment

Horner's Syndrome in Cats: Causes, Symptoms & Treatment

Horner's syndrome is a neurological disorder that can affect your cat's eye and facial muscles. Today, our Renton veterinarians explain what can cause the condition. We also list symptoms and discuss treatment and management.

What is Horner's syndrome?

Horner's syndrome is caused by dysfunction in the sympathetic nervous system.

Some people wonder whether Horner's is classified as a disease or a disorder in cats. It's officially referred to as a neurological disorder that affects the muscles around the eyes and face. Typically, this condition only impacts one side of the face, but can affect both sides in rare cases. 

What is the sympathetic nervous system?

The sympathetic nervous system is part of the body's autonomic nervous system, and controls the body's automatic or involuntary functions. These include the normal functioning of the face and eye muscles and can cover muscle tone, pupil dilation and constriction, and blinking. 

What causes Homer's syndrome in cats? 

The pupil can be affected by both the sympathetic and parasympathetic systems. It may become impossible for the eye muscles to contract and relax. Some triggers for this can include: 

  • Blood Clots - An abnormal blood clot (infarction) in the spinal cord can cause a lesion that affects typical function, leading to Hormer's syndrome. 
  • Eye Diseases - Certain eye conditions, such as conjunctivitis, glaucoma, and keratitis, can cause symptoms related to Horner's syndrome. 
  • Middle Ear Infection - Some facial nerves travel into the middle ear. If the middle ear becomes infected or inflammation is present, this can lead to Horner's syndrome. 
  • Trauma - Horner's syndrome can result from Injuries to the head, neck, or spine, which can be caused by various triggers such as bite wounds from another animal, certain procedures such as thoracic surgeries, and car accidents. 
  • Tumors - A tumor can affect the nerve fibers in the brain, brain stem, or spinal cord.  

Despite all of these, it's important to keep in mind that about 40% of Horner's syndrome cases are idiopathic, meaning the cause remains unknown. The above are just some issues we already know can cause Horner's syndrome. 

What are the symptoms of Horner's syndrome?

When it comes to identifying Horner's syndrome in cats, our veterinary ophthalmologists will look for symptoms such as: 

  • Conjunctival Hyperemia: The third eyelid may appear red and raised or protruded. 
  • Enophthalmos: The eye appears sunken.
  • Miosis: The pupil will constrict or appear smaller than usual. 
  • Ptosis: The upper eyelid drops on the affected side. 

Is there treatment for Horner's Syndrome?

If Horner's syndrome has become an issue for your cat, your veterinarian may recommend eye drops as a treatment for some symptoms, such as constricted pupils. The vet may suggest eye drops with phenylephrine to make the pupil bigger and eye lubricants to prevent corneal ulcers from exposure keratitis. Horner's syndrome typically disappears on its own, with time. 

However, if another eye condition is causing your cat’s Horner’s Syndrome, it’s important to have a veterinarian treat that disease. As a symptomatic treatment, eye lubricants and phenylephrine drops may help.

How should I care for my cat with Horner's syndrome? 

It's important to bring your cat in for a regular checkup with your vet to have their eyes and other areas of their body checked for new, developing, or changing conditions and health issues. 

Our veterinary ophthalmologists can work with your vet to monitor and manage your cat's condition and to help keep their eyes as healthy as possible. 

What is the prognosis for a cat with Horner's Syndrome?

This depends on the underlying cause and your cat's general health. If caused by another disease, Horner's Syndrome will generally resolves after the disease does. Cats who develop Horner's Syndrome as thoracic surgery often improve too.

If Horner's syndrome is a result of a bulla osteotomy, about 75% will recover from Horner's Syndrome.  

Some cats only experience a partial recovery. They might still have a drooping eyelid, sunken eye, or shrunken pupil. But these are cosmetic and shouldn't affect your cat's quality of life.

Can Horner's syndrome be prevented?

Most causes of Horner's syndrome in cats are not preventable. You can best help your cat avoid physical trauma by keeping them indoors, which can help keep them from getting into fights with other animals, or falling or jumping from balconies or other high platforms. 

Debris or redness in your cat's ears should be addressed as soon as possible by a veterinary ophthalmologist. 

Note: The advice provided in this post is intended for informational purposes and does not constitute medical or behavioral advice regarding pets. Please make an appointment with your vet for an accurate diagnosis of your pet's condition.

Is your cat displaying signs of Horner's syndrome or another eye condition? Contact our Renton vets to book an appointment with our veterinary ophthalmologist.

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We are accepting new patients! Our experienced vets are passionate about the eye health of animals. Talk to your vet today about getting a referral to Northwest Animal Eye Specialists serving patients from Renton, Kirkland, and the surrounding areas.

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