Horner's Syndrome
Horner's Syndrome
Horner's syndrome is a collection of clinical signs that are seen together and often have a limited number of causes. These clinical signs occur due to damage to the sympathetic nerve supply to the eye.
What's really going on
The signs of Horner's syndrome include a constricted pupil that does not dilate (miosis), drooping of the upper eyelid (ptosis), a sunken appearance of the eye (enophthalmos), and an elevation of the third eyelid. These symptoms are not painful though they may interfere with vision due to the third eyelid elevation.
The sympathetic nerve supply to the eye originates at the base of the brain and has 3 sections. Damage can occur anywhere along this nerve pathway. Damage within the brain and spinal cord is called First order Horner's syndrome. Damage between the chest cavity and the base of the skull is called Second order Horner's syndrome. Damage between the base of the skull and eye is called Third order Horner's syndrome, which is the most commonly seen form in dogs and is most often associated with inner or middle ear disease.
How a specialist helps
We can temporarily treat the symptoms of Horner's syndrome with eye drops. If your pet is having difficulty with vision, your veterinary ophthalmologist may prescribe eye drops called sympathomimetics that mimic the sympathetic system supply. Determining and treating the underlying cause of this syndrome can be important as some diseases are very serious and potentially life-threatening. Luckily, most patients have few complications from Horner's syndrome and the signs clear up on their own in a few months.