What is Horner's Syndrome in Cats?

The eyes of your cat can tell you more about its neurological health than you’d expect. If you notice that your cat’s eye is different from the other, there’s a possibility that your cat might have Horner’s syndrome. The physical attributes of the syndrome that you should look for includes a sunken eye, droopy eyelids, an abnormally smaller pupil compared to the other eye, and even an exposed nictitating membrane or third eyelid. All of these physical manifestations point directly to the neurological condition that affect the eyes and facial muscles of your cat.

What is Horner’s syndrome?

A collection of physical symptoms is exactly what Horner’s syndrome is, but it’s nothing more than that. Horner’s syndrome is not the actual disease that causes the syndrome. When these physical symptoms present themselves, there’s usually an underlying problem or disease in the neurological pathways in your cat’s brain that requires immediate attention. When Horner’s syndrome presents itself, the goal is to figure out what disease is causing it.

Normally, the eye muscles of your cat help to keep each eyeball in its proper place in the eye socket. These muscles are also responsible for keeping your cat’s eyelids open. A normal healthy cat’s eye will have the nictitating membrane retracted in its proper place in the corner of each eye, and the pupil will dilate accordingly upon exposure to low light.

When a cat develops Horner’s syndrome, it means that damage has been incurred on the sympathetic nervous system. This damage is basically what causes the muscles behind the various parts of one eye to look different and be all skewed. The sympathetic nervous system pathway to the eye happens to be extremely long as well. This makes diagnosing the underlying problem a little bit more complicated. This pathway also doesn’t just stay inside the brain. The pathway actually travels throughout the body, so the damage could be at a wide range of locales in the body. Any damage to any part of this pathway could lead to the development of Horner’s syndrome, and in order to treat Horner’s syndrome, the underlying damage has to be addressed.

Symptoms of Horner’s syndrome

As previously mentioned, Horner’s syndrome manifests itself around one eye of your cat. The four symptoms are quite distinctive and easy to identify, and they all have to occur at the same time for the condition to be legitimately Horner’s syndrome. One eye will look slightly smaller than the other due to drooping eyelids. You’ll also see the nictitating membrane exposed on the corner of the same eye. You’ll also see that the pupil on the same eye is smaller and unable to dilate properly in low lighting. In addition to these four symptoms, the eye may feel warm to touch, and the skin around the eye may have an abnormally pinkish hue.

Diagnosis of Horner’s syndrome

To properly diagnose Horner’s syndrome, a veterinarian will have to perform a complete physical and neurological evaluation on your cat. Even if you only see a couple of the symptoms present, it will be a smart move to take your cat to the vet for a possible early diagnosis. If your veterinarian suspects Horner’s syndrome, he or she should be able to localize the damage on the sympathetic nervous system pathway through a series of tests. Some of these tests might include blood work, urinalysis, and imaging such as x-rays, MRI, or a CT scan.

Once the damage has been localized, then a treatment plan can be started. If the cause of Horner’s syndrome is treatable, then your cat should recover from the syndrome completely. However, if a severe neurological injury or disease is causing the damage to the pathway, then your cat will likely sustain the symptoms of Horner’s syndrome for the rest of its life. There are situations when a cat will maintain the symptoms of Horner’s syndrome even after the underlying problem has been treated.

In either case, it’s important to pay attention to your cat’s eye health to catch Horner’s syndrome early on or to just keep its ocular health in check. Even if your cat doesn’t have Horner’s syndrome, you’ll want to make sure that its eyes are not experiencing other problems that might be affecting its vision or overall wellbeing.