CVMA | Documents | Horner’s Syndrome in Cats

Horner’s Syndrome in Cats

December 7, 2012

Horner’s Syndrome is a nervous system disorder which results from the malfunction of a nerve and produces symptoms in the eyes. When a cat has Horner’s Syndrome, the pupil becomes small, the upper eyelid droops and the eyeball is recessed into the globe more than normal. The third eyelid is sometimes visible and may be sitting partly up over the eye. These symptoms generally occur on one side only but may be present in both.

There are a range of underlying conditions which may lead to nerve dysfunction/Horner’s Syndrome in cats. The signs of Horner’s may be produced if  a problem occurs anywhere along the nervous tracts which run between the brain and the eye. The pathway runs from the brain, via the brain stem, through the spinal cord, down through the thorax (chest), then through the ear, and along a branch of cranial nerve V. The affected pathway is termed Sympathetic. The word does not have the same meaning here as the word you know in its common use but rather refers to one part of the body’s autonomic nervous system.

Horner’s Syndrome is not life-threatening and will often clear up on its own. In cats, almost half of the cases of Horner’s Syndrome have no obvious identifiable cause (idiopathic). In these instances, without a specific cause to treat, recovery can take 16 weeks or more. Some cats never normalize. If the underlying cause of the Horner’s is diagnosed, specific therapy tailored to the inciting disease will be performed.

Examples of conditions associated with Horner’s include:

  • Inflammation, infection of nerve tissues, middle ear
  • Trauma
  • Tumors of the spine, brain stem or nerves