Horner's syndrome is more of a collection of clinical symptoms than a true diagnosis. Nevertheless, horner's syndrome in dogs is a result of neurological insufficiencies that result in ocular symptoms. There are numerous causes from trauma, masses, or inner ear infections. There is no definitive treatment for Horner's syndrome in dogs and treatment is targeted at the underlying cause. Horner's syndrome only affects one eye as having horners in both eyes is very rare and usually involves diseases in the brainstem.
The causes of Horner's syndrome in dogs
It is important to understand the neurological pathway to better appreciate the causes of horner syndrome in dogs. The neurological pathway travels from the midbrain to the thoracic spinal cord and then back up through the neck, and through the ear to eventually dilate the pupil in the eye. Any defect that affects this pathway can cause Horner syndrome. The most common causes however are:
- Idiopathic (unknown cause or reason) *Most common*
- Trauma
- A mass in the chest
- Inner ear infection
- Cancer of the nerves along the pathway
- Neuropathy, such as hypothyroidism
The age groups and breeds that are most affected by Horner's syndrome
Any age group can develop Horner's syndrome but most are 5-8 years of age. Common breeds affected are the Golden Retriever, Labrador retriever, Collie, Shetland sheepdog, Weimaraner, and Doberman pinscher. Both males and females are equally affected.
The clinical symptoms of Horner's syndrome in dogs
A typical Horner syndrome presentation will include 3 features:
- Miosis (constricted pupil)
- Ptosis (droopy upper eyelid)
- Enophthalmos (sunken eyeball); Elevated third eyelid as a result
Having all 3 of these symptoms confirms Horners syndrome. Your veterinarian should perform a thorough, detailed physical examination in an attempt to determine the underlying cause of Horner syndrome in your dog. Your veterinarian may also recommend blood work and chest X-rays to identify any underlying conditions that may be causing Horners syndrome.
Treatment and prognosis for Horner's syndrome in dogs
Treatment is directed toward the underlying problem. There is no known treatment for Horner syndrome itself. The prognosis for idiopathic diseases is generally good with spontaneous improvement typically occurring within 8 weeks. Some animals only recover partially and recurrence is rare.
Horner's Syndrome is a collection of symptoms that result from neurological insufficiencies. There are numerous causes of horners syndrome in dogs, but the most common are trauma, masses, or inner ear infections. Treatment varies depending on the underlying cause and prognosis is generally good with spontaneous improvement typically occurring within 8 weeks. If you notice any clinical signs of horners syndrome in your dog contact your veterinarian immediately to help determine what's wrong.