Horners Syndrome in Dogs

Horners syndrome is a rare condition that may affect canines, causing lack of control over the facial muscles. The facial muscles are controlled by the sympathetic nerves and when these are affected, the dog may display some unusual symptoms. The condition is treatable if the causes are detected and dealt with.

Causes of Horners Syndrome

Horner’s syndrome is typically caused by an injury affecting the sympathetic nerves. Other possible causes of this condition include:

• Traffic accidents that cause injuries to the head or the spinal cord
• Bites, affecting the head or the spinal cord
• Ear infections that are in an advanced stage and affect the inner ear
• Intervertebral disk disease (affecting the vertebrae in the neck area)
• Eye infections that involve the orbit
• Brain tumors/ tumors behind the eyes
• Tumors in the spinal cord area

However, in some cases (up to 50% of all dogs with Horner’s syndrome), the condition is idiopathic (has no known causes). Some dog breeds (i.e. Golden Retrievers) are more prone to the disease.

Symptoms of Horner’s Syndrome

The sympathetic nerves control the facial muscles and the blood vessels and there will be several symptoms present in a pet with Horner’s syndrome:

• Reduced pupil size (miosis), but only in 1 of the eyes, typically in the side that has been injured
• Visible third eye lid
• Drooping of eye lid or even closed eye (only on the affected side)
• The face will feel warmer, due to the dilatation of the blood vessels

The symptoms may affect only 1 side of the face, which can make it easier to detect the area that may have been injured.

Diagnosis for Horners Syndrome

A dog can be diagnosed with Horner’s syndrome judging by the symptoms displayed. However, some blood tests will also be needed, to establish the possible causes.

The vet will also examine the dog and see if there are any visible injuries that may have caused the symptoms.

X-rays, CAT scans or a MRI may be performed to detect injuries or tumors.

If the vet finds no causes and the dog is not affected by any other condition, he will consider that the dog is affected by Horner’s syndrome and this is most likely idiopathic.

Treatment Options for Horners Syndrome

Dogs that are affected by Horner’s syndrome may be treated if the condition has known causes.

If the dog has a head or spinal cord injury, treatment and surgery will be the solution. Once the dog is cured, the symptoms of Horner’s syndrome will also disappear. If the dog has a tumor, this should be biopsied and if possible, surgically removed. 

Ear infections should be treated immediately with antibiotics.

If the condition is idiopathic, the symptoms will typically go away within 8 weeks and there is no need for treatment. However, the condition may be recurrent.