Pet Education Cats
Pet Education Cats Pet Education Cats Pet Education Cats

Learn about Vetco
Dog Food Cat Food New Brands - Healthy Choices Just Added!
Free Shipping on orders over $49
Video Center
Horner's Syndrome in Cats
Veterinary & Aquatic Services Department, Drs. Foster & Smith
Muscle & Nervous System Diseases
Print Article | Email Article
Bookmark and Share
Click here for a pdf version of this article. 
What is Horner's Syndrome, and what causes it?

Horner's Syndrome is a group of signs that occurs when specific muscles of the face lose their stimulation by certain nerves, specifically the sympathetic nerves. It is caused by some type of injury to, or lesion of, the nerves. The injury may occur at the level of the brain, upper spinal cord, or between the spinal cord and the face. In the cat, the most common causes are:

  • Idiopathic
  • Car accidents with trauma to the head, neck, or chest
  • Bite wounds
  • Foreign body
  • Tumor of the spine
  • As a result of a treatment (e.g.; ear cleaning) or medication

Approximately 25-42% of the cases of Horner's Syndrome in cats are idiopathic.

What are the signs of Horner's Syndrome? Horner's Syndrome

The classic signs of Horner's Syndrome occur on the same side of the face as the injury, and include:

  1. Small pupil size (miosis)

  2. Protrusion of the third eyelid

  3. Drooping of the upper eyelid (ptosis)

  4. Sunken appearance to the eye (enophthalmos)

  5. Dilation of blood vessels on affected side of the face, which makes the area feel warmer to the touch

How is Horner's Syndrome diagnosed?

Horner's Syndrome is diagnosed by the presence of the signs listed above. What is more difficult, is the diagnosis of the cause of the condition. A complete physical and neurologic exam, radiographs (x-rays), a chemistry panel, complete blood count (CBC), and perhaps a CAT scan or MRI will help determine the cause. Epinephrine may be administered to the eye to assist in locating the site of the injury by measuring the time between administration and dilation of the pupil. When the injury to the nerves occurs outside of the brain and spinal cord, the epinephrine will cause the pupil to dilate within 20 minutes of administration. If the lesion is in the brain or spinal cord, pupil dilation generally does not occur until 30 or 40 minutes after the epinephrine is administered.

How is Horner's Syndrome treated?

Depending upon the location of the injury, phenylephrine eye drops are administered to relieve the clinical signs. The underlying cause such as a bite wound or middle ear infection should be treated. In cases of idiopathic Horner's Syndrome, the condition often resolves after 6-8 weeks. Horner's Syndrome caused by injuries to nerves outside of the brain and spinal cord generally have a better prognosis.

References and Further Reading

Collins, BK. Neuro-ophthalmology. In Ettinger, SJ; Feldman, EC. Textbook of Veterinary Internal Medicine. W.B. Saunders Co. Philadelphia, PA; 2000.

Cottrill, NB. Differential diagnosis of anisocoria. In Bonagura, JB. (ed) Kirk's Current Veterinary Therapy XIII: Small Animal Practice. W.B. Saunders Co. Philadelphia, PA; 2000.

Slatter, D. Fundamentals of Veterinary Ophthalmology. W.B. Saunders Co. Philadelphia, PA; 2001.

Click here for a pdf version of this article.   
Print Article | Email Article

Facebook YouTube Blog Connect with us

Subscribe to email newsletters:
featuring helpful articles, tips and online only product specials from Drs. Foster & Smith. Learn more here !

About Us Article Reprints Awards & Memberships Request a FREE Catalog Tell a Friend
Meet Our Staff Terms & Use Site Map Free Newsletters Links to Us
Visit our other websites: Doctors Foster and Smith Pet Supplies - Quality Aquatic Life Direct to Your Door
For product information, call 1-800-826-7206

Copyright © 1997-2016, Petco Wellness, LLC. All rights reserved.
2253 Air Park Road, P.O. Box 100, Rhinelander, Wisconsin, 54501.
Terms of Use | Privacy Policy | Your CA Privacy Rights | Copyright Claims | Pet Medical Records Policy