Horner’s syndrome in Cats: what it is, causes, symptoms and treatment


Horner’s syndrome in cats is a disease that begins suddenly and should not be underestimated. Let’s find out the causes, symptoms and how to treat cat.

Anyone who has a cat knows perfectly well that in order for it to live well, it is necessary to monitor not only its nutrition but also its health constantly.

In fact, there are many pathologies that can affect our cat suddenly, some mild that heal within a few days but others much more complex that if not treated promptly can cause serious and permanent disturbances.

One of the little known pathologies that can affect the cat is Horner’s syndrome : a neuro-ophthalmological condition whose diagnosis is very difficult and has really annoying and abnormal symptoms. Symptoms that, however, are most often confused with those of other pathologies.

Precisely for this reason it is important to know what Horner’s syndrome in cats consists of, what are the causes that trigger it, the symptoms and what to do to ensure a quick recovery for the cat.


Horner’s syndrome in cats: what is it

Horner’s syndrome in cats, which most often begins suddenly, occurs as a result of damage or malfunction of the sympathetic nervous system.

Also known as “oculosympathetic paralysis”, it is not difficult to understand that the cat’s eyes and facial muscles are affected, and it is certainly not to be underestimated.

When this pathology occurs, there is a real interruption of communication between the brain and the eyes, which lose or “see” their functionality diminishing.

Most of the time it is unilateral, that is, it is only one side of the face that is affected, and consequently only one eye, but there are cases in which it is bilateral (obtaining a diagnosis in this circumstance is much more complicated).

Furthermore, its symptoms are most often confused with those of other pathologies, and it is precisely for this reason that it is difficult to recognize it immediately.

Horner’s syndrome in cats is not considered a serious disease, but it becomes so when the causes that triggered it are serious, that is, underlying diseases connected to it.


What are the causes

Recent surveys have stated that in 50% of cases it is not possible to trace the cause that triggered Horner’s syndrome in cats, which is why it is most often defined as “idiopathic”.

But as previously mentioned, it has been established that this syndrome occurs due to damage or malfunction of the sympathetic trunk, with the consequent interruption of communication between the brain and the eyes.

But what is the cause of this damage? Following the many cases recorded, it was possible to classify some causes connected to this “problem” in the cat, the most common are:

  • Trauma to the neck, chest and eye : sometimes due to an accidental bite or fall;
  • Otitis media , and in rare cases internal;
  • Facial nerve paralysis ;
  • Facial muscle atrophy ;
  • Infections affecting the central nervous system ;
  • Surgery, involving the rib cage;
  • Chest drainage ;
  • Pathologies affecting the intervertebral discs ;
  • Mediastinal tumors , which affect the area between the sternum, spine and lungs;
  • Inflammations and tumors of the trigeminal nerve.

But still: myelitis, tetanus, dehydration, diabetes mellitus, hypothyroidism and many more. It is not impossible to admit that the diagnosis for this pathology is really complicated, its known causes are many and only after a careful medical examination will the vet be able to establish the right diagnosis for the cat.


Symptoms of Horner’s syndrome in cats

As we have seen, the causes that can trigger this pathology in cats are so many, as are its symptoms: which we often confuse with those of other diseases.

In our eyes it will be almost impossible to say that the cat is affected by Horner’s syndrome, but our trusted veterinarian will be able to do so following a specific visit and the support of a neurologist.

But what are the symptoms of this disease that it is good to know and be able to identify? Let’s find out:

  • Anisocoria : If unilateral it is possible to notice a difference in the size of the pupils in the cat, in practice one will be more dilated than the other;
  • Miosis : There will be a narrowing of the “affected” pupil;
  • Enophthalmos : The affected eye, or both if bilateral, will be more sunken;
  • Prolapse of the third eyelid : The nictitating membrane will be enlarged and therefore its “exit” from the eyelid will be highlighted;
  • Eyelid ptosis : There will be a lowering of the upper eyelid, the eye will be almost closed. This condition is commonly known as “drooping eyelid”;
  • Conjunctival hyperamy : redness of the eyes ;
  • Conjunctival discharge ;
  • Increase in skin temperature : Affecting the affected area.

A clarification must be made: Horner’s syndrome in cats is most often unilateral so if we pay the utmost attention to possible visible “variations” between one eye and the other (facial asymmetry) it will be much easier to associate these symptoms with this pathology.


Diagnosis and treatment

Horner’s syndrome in cats is absolutely not to be underestimated. It is important to take your cat to the vet immediately as soon as we notice any of the symptoms listed above or facial asymmetry.

Thanks to the support of a neurologist, the veterinarian will subject the feline to a very careful and specific examination: radiography, magnetic resonance and a CT scan are the most important tests to which the cat will be subjected.

Thanks to these imaging tests it will be possible to find out what is the cause that triggered this syndrome : if a neurological lesion or intracranial spinal cord, or if an underlying pathology was damaging the sympathetic nervous system. Only in this way will it be possible to treat cat in the best way.

Unfortunately, to date, a specific cure for Horner’s syndrome in cats does not exist, as damage to the nervous system is permanent. However, it will still be possible to subject your cat to symptomatic drug therapy, the same thing when you are not able to discover the cause.

On the other hand, in the event that the damage is due to a further pathology, the veterinarian will proceed by administering to the cat a specific treatment for this underlying pathology : once this has been resolved, we will witness the regression of Horner’s syndrome in the cat.


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