How to prevent and treat Horner’s syndrome in cats

Horner’s syndrome refers to a set of changes to the appearance of the eye that occur when the nerves supplying the eye are damaged or aren’t working properly. Symptoms of Horner’s syndrome usually only appear on one side of the face. Signs are an elevated third eyelid, constricted pupil, slightly droopy eyelid, and retraction of the eyeball deeper into the socket. Horner’s syndrome can be caused by a wide variety of health issues, such as ear infections, traumatic injury, and tumors that affect the sympathetic nervous system. In some cases, the underlying cause can’t be identified. Treatment options vary depending on the cause of the symptoms.

It’s important to seek veterinary care when you notice changes to your cat’s face or eyes. Learning more about Horner’s syndrome can help you know what to expect, including:

• Symptoms of Horner’s syndrome in cats
• What causes feline Horner’s syndrome
• How the cause of Horner’s syndrome is diagnosed and treated in cats
• When owners can and cannot prevent Horner’s syndrome

Symptoms associated with Horner’s syndrome are commonly seen with many other health problems, so it’s important to get an accurate diagnosis from a veterinarian. Some causes of Horner’s syndrome, such as traumatic injuries and complications of diseases that cats are commonly vaccinated for, can be prevented, while others cannot. If you’re unsure if your cat’s eyes appear normal or want more information on how to prevent Horner’s syndrome, an online vet is a convenient source of professional advice.

Horner’s syndrome describes a collection of clinical signs that occur when the nerves supplying the eye and its surrounding structures are disrupted. The syndrome itself is not a diagnosis and can be caused by many different health issues.

Horner’s syndrome consists of four symptoms:

• Constricted pupil
• Elevated third eyelid
• Retraction of the eyeball into the head
• Slight drooping of the eyelid

“Symptoms of Horner’s syndrome develop on only one side of the face in most cases,” explains Dr. Jo Myers, a veterinarian on the Vetster platform. “Some signs may be easier to detect than others, and all four may not be apparent at once.” While the “classic” presentation of Horner’s syndrome includes all four signs, not all of the signs have to be present, and they may come and go.

Horner’s syndrome itself is not painful and does not affect vision, though the underlying cause, such as an injury, may cause pain.

Horner’s syndrome occurs when trauma or disease disrupts the function of the sympathetic nervous system that supplies the face and eyes.

The sympathetic nervous system is related to the reflexes and controls bodily functions that occur automatically and without awareness, such as pupil dilation and positioning of the eye in the socket. The sympathetic pathway to the eye is long, involving the brain, spinal cord, chest cavity, neck, middle ear, and eyes. Disruption anywhere along the pathway can lead to Horner’s syndrome.

Treatment options and prognosis depend on the underlying cause of the nervous system disruption.

• Injuries: Head, neck, chest, or spinal cord injuries may damage sympathetic nerves. Treatment often focuses on stabilizing the cat, controlling pain, and allowing time for healing. Symptoms may improve gradually, depending on the type of injury.
• Infections: Middle ear disease is one of the most common causes of nerve disruption leading to Horner’s syndrome in cats. Veterinarians typically prescribe antibiotics and occasionally antifungals to treat infections in the ear or surrounding tissues. Symptoms typically improve quickly as the infection goes away.
• Tumors: Chest, neck, or brain tumors can put pressure on the nerve pathway. Depending on the tumor’s type and location, treatment may involve surgery, radiation, or chemotherapy. Prognosis depends on how advanced the disease is.
• Other systemic or neurological conditions: Systemic or neurological disorders, such as intervertebral disc disease, vascular disease (stroke-like events), or nerve damage in the shoulder region, require specific therapies tailored to those diseases. Prognosis varies between conditions and based on how the cat responds to treatment.

Many cases of Horner’s syndrome in cats are idiopathic, meaning there is no identifiable cause. If no known cause can be identified, there is no specific treatment for Horner’s syndrome. In many cases, cats with idiopathic Horner’s syndrome spontaneously get better without treatment. Depending on the underlying cause, some cats may never improve. These symptoms are not usually associated with pain or other health issues.

Prevention efforts focus on reducing the risk of underlying conditions that may lead to Horner’s syndrome. Some common underlying causes, like ear infections and injuries, can be prevented:

• Keeping cats indoors to help prevent injuries, fights, and the spread of infectious diseases
• Up-to-date vaccinations to reduce the risk of upper respiratory infections that may affect the middle ear
• Seeking veterinary care for upper respiratory symptoms like coughing, sneezing, and nasal or eye discharge
• Seeking veterinary care for ears that are red, swollen, crusty, itchy, or painful
• Year-round parasite prevention to help protect against pests like ear mites

Ear infections are one of the most common causes of Horner’s syndrome in cats, so it’s important to seek early diagnosis and treatment any time your cat shows symptoms that could lead to one. Not all causes can be prevented, but many can be caught before symptoms show with routine veterinary care and checkups.

It’s important to talk to a veterinarian if you notice changes in your cat’s eye health, such as unequal pupils, a raised third eyelid, or other changes to the eyes. Some eye and neurological conditions have similar symptoms to Horner’s syndrome, such as changes in pupil size, eyelid position, or third eyelid elevation. These conditions include:

• Eye injuries, infection, or cancer
• Haws syndrome
• Feline infectious peritonitis (FIP)

In some cases, an in-person examination is necessary to look deeper into the eye or ear, since these areas can’t be fully evaluated over video. Examination helps identify or rule out underlying problems, such as infection, injury, or tumors along the nerve pathway.

However, given that many cases of Horner’s syndrome are idiopathic and resolve on their own, an in-person visit may not always be necessary. While a more thorough hands-on exam always provides additional insight, it’s not always practical or accessible, especially when a cat is otherwise healthy and showing no other symptoms. A virtual veterinarian can play an important role in these situations by:

• Reviewing your cat’s history and symptoms
• Observing visible changes through video and photos
• Providing guidance on how urgent the situation is
• Helping you understand what tests or in-person care may be needed next
• Offering specific treatment in some cases, including prescriptions

The level of care a virtual veterinarian can provide varies depending on local laws and regulations. To learn more about what’s available where you live, visit this interactive map from the Virtual Veterinary Care Association.

While Horner’s syndrome sometimes resolves on its own, there are no proven home or over-the-counter treatments that can speed recovery or safely correct the nerve dysfunction. Because the condition can look similar to other eye or neurological problems, trying home remedies or natural products can delay proper diagnosis or even cause harm.

The best way to help an affected cat is to seek professional veterinary guidance. A veterinarian can confirm that the signs are truly consistent with Horner’s syndrome, rule in or out underlying issues that require specific treatment, and provide advice on how to monitor your cat safely while recovery takes place.

What are the signs of Horner’s syndrome in cats?

Signs of Horner’s syndrome in cats usually affect only one side of the face and include a constricted pupil, an elevated third eyelid, retraction of the eyeball in the socket, and a slightly drooping eyelid. Some symptoms may be more pronounced than others, and an affected cat may or may not have all four signs of Horner’s syndrome.

Can I treat my cat’s Horner’s syndrome at home?

Because Horner’s syndrome isn’t a single disease but rather a group of signs that can result from many different underlying problems — some of which can be serious — there’s no safe or effective home treatment. The best thing to do is seek veterinary guidance. A vet can determine whether your cat’s symptoms are truly due to Horner’s syndrome, identify or rule out underlying conditions, and recommend the most appropriate care or monitoring plan for your cat’s unique situation.

Can Horner’s syndrome in cats go away on its own?

Some cases of Horner’s syndrome, especially idiopathic Horner’s syndrome, can go away on their own. In other cases, the symptoms often go away once the underlying health issue is appropriately treated. Occasionally, and depending on the underlying cause, some cats may have the clinical signs of Horner’s syndrome for the remainder of their life. It’s important to talk to a veterinarian to determine the underlying cause of your cat’s symptoms and get appropriate treatment.

Disclaimer: This article, its content, and its related references do not constitute veterinary advice and should not be considered a substitute for veterinary care. If your pet is showing any symptoms that could indicate a medical emergency, please seek immediate emergency care.