Horner’s Syndrome in Cats - Causes and Treatment

It is challenging to explain the exact mechanisms that can lead to the appearance of feline Horner’s syndrome. It results from a communication error in the affected cat’s nervous system, which then manifests itself as problems in their eyes. This issue stems from a problem in the sympathetic nervous system, part of the autonomic nervous system. These are the controls the body uses for automatic or involuntary actions.

This neurological disorder in cats can be unilateral or bilateral, depending on whether it affects one or both eyes, respectively. According to a report by Iowa State University, the ‘syndrome...is characterized by enophthalmos, ptosis, miosis, and anhidrosis (due to paralysis of the sympathetic innervation of the eye)’.^[1]

Understanding these terms is crucial: enophthalmos refers to the retraction of the eyeball within the orbit, ptosis is the drooping of the eyelid, miosis is the constriction of the pupil, and anhidrosis refers to the lack of sweating in the affected area, which in cats, is the inability to properly moisten the eye.

As mentioned earlier, Horner's syndrome affects the sympathetic nervous system of cats. As this system controls autonomic movements, symptoms often affect parts of the body known for involuntary action, specifically the eyes. Horner’s syndrome in cats can be observed in a cat that is showing the following signs:

• Protrusion of the nictitating membrane (third eyelid): this membrane is in the cat's eye, between the eyeball and the eyelid. When issues such as Horner's syndrome and other conditions occur, the membrane extends over the eye to protect it. It is not only eye conditions that cause this to happen but also other systemic problems. For more, we also recommend reading our article on third eyelid showing in cats - causes and treatment.
• Miosis: defined as the fixed appearance of the pupil, which is permanently contracted.
• Palpebral ptosis: consisting of the slight droop of the upper eyelid on the eye.
• Enophthalmia: the eye seems smaller in size, appearing retracted in its socket.

Any of these symptoms warrant a veterinary consultation. Even if the symptoms are not due to Horner's syndrome, their presence suggests a potential neurological problem.

Image: adelaidevet.com.au

The underlying cause that triggers Horner’s syndrome in cats is not always easy to determine. In these cases, the origin is idiopathic, meaning the exact cause is unknown.

One of the most common causes of Horner’s syndrome in cats is linked to physical trauma. Such trauma can occur for various reasons. The cat may have fallen from a significant height, been involved in a road traffic collision, or been in a fight with another animal. Since these incidents may have happened without our knowledge, pinpointing the exact cause can be challenging.

Another frequent cause of Horner’s syndrome is otitis in cats, which can affect the outer, middle, or inner parts of the ear. For example, when a cat suffers from a severe ear infection or inflammation (otitis), it can cause damage to the cat’s nervous system, particularly if the infection is left untreated.

Causes of Horner’s syndrome in cats can also include:

• Poisoning
• Other types of bacterial, viral, or fungal infections
• Tumors in cats

For related information, we recommend reading our article where we discuss common ear problems in cats.

It should be noted that certain surgeries or procedures involving the neck or chest could inadvertently damage the sympathetic nerves, potentially leading to Horner’s syndrome.

Horner's syndrome symptoms are unmistakable when they appear together. However, identifying the underlying cause of the syndrome is crucial. A veterinarian will likely inquire if you suspect your cat has fallen or been involved in a fight. As mentioned earlier, you may not have witnessed the incident. The cat may not even show other signs of pain as they are adept at concealing discomfort.

A veterinarian can also differentiate Horner’s syndrome causes by performing blood tests, X-rays, MRIs, or CAT scans. These tests provide the necessary information to apply the correct Horner’s syndrome treatment. Additionally, Horner’s syndrome in cats usually requires a neurological, ocular, and otic examination.

Once the cause is established, Horner's syndrome in cats treatment can begin. It's crucial to address any underlying issues, as this is key to resolving the symptoms.

The typical symptomatology of Horner’s syndrome can alleviate on its own in a matter of weeks. Nevertheless, a veterinarian will still need to guide the appropriate treatment. If your cat has suffered an accident or an attack, it's essential to assess whether they have additional injuries, such as bone fractures. In such cases, a cat usually requires analgesics, anti-inflammatories, and possibly antibiotics.

If it is a case of otitis in cats, the cause needs to be identified to treat it adequately. Anesthesia may be administered to a cat suffering from this syndrome, allowing the veterinarian to examine and clean the ear thoroughly. In many cases, tumors can also be treated, but prognosis will vary based on the specific case.

When the underlying cause is an infection, the veterinarian will need to determine the responsible pathogen. In viral infections, supportive therapy will be used to manage symptoms. For bacterial and fungal infections, the corresponding antibiotic and antifungal medications will be administered.

Does Horner's syndrome in cats go away?

As noted earlier, Horner's syndrome can alleviate on its own. In many instances, once the underlying problem is addressed, the symptoms that constitute Horner's syndrome disappear. In some cases, the underlying cause may remain unidentified, complicating treatment. Other cats may experience more permanent damage to their sympathetic trunk (part of the sympathetic system). Fortunately, feline Horner's syndrome is relatively rare.

In cases where the syndrome does not resolve spontaneously, more extensive intervention may be necessary, and ongoing veterinary care will be crucial to manage the condition effectively.

If you found this article helpful, you may like to have a look at our following YouTube video where we discuss the 10 most common diseases in cats:

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Horner’s Syndrome in Cats - Causes and Treatment, we recommend you visit our Neurological diseases category.