Horner syndrome

Horner syndrome is a rare disease which affects the sympathetic nerves that supply from the brain to the face and eye.


Horner syndrome shows a combination of signs and symptoms. It is characterized by a triad of symptoms namely

  • Miosis: constricted pupil which persists
  • Anhidrosis: loss or decrease of hemifacial sweating (on the affected side)
  • Partial ptosis: drooping eyelids

The other symptoms include:

  • Difference in the pupil size (black part of the eye) between the two eyes
  • Delayed or inadequate opening of the affected pupil in dim light
  • Sunken eyeballs into the face

Causes and Risk factors

Horner syndrome occurs as a consequence of interruption of the nervous supply from the brain to the face and eye of one side of the body. The following are the causes of Horner syndrome:

Nerve fiber injury which can occur due to:

  • Injury to the main artery of the brain
  • Injury to the nerves supplying the base of the neck
  • Tumor in the top of the lung
  • Stroke or tumor or any other damage to a part of the brain
  • Migraine or cluster headache
  • Surgery of the nerve fibers to relieve pain

Rarely, Horner syndrome can be congenital, i.e. it is present at the time of birth. Such cases are detected by a lack of pigment in the iris of the eye.


Treatment is based on the cause of the condition. There is no treatment for Horner syndrome. Treatment is focused on the underlying condition which has caused the Horner syndrome.

In the case of tumors of the nervous or endocrine system, surgical removal of the tumors, chemotherapy or radiotherapy may be beneficial.


Horner syndrome does not produce any direct complications. But the complications can arise from the underlying cause or its treatment.

For a proper diagnosis of Horner syndrome, your doctor initially will conduct a thorough physical examination of the eye. Medical history of the patient is also taken to get a clue of the underlying cause.

Pharmacological testing is done by putting drops of the drugs such as epinephrine, phenylephrine, or hydroxyamphetamine into the suspected eye to check for the reaction of the pupil size to these dilation causing drugs. By comparing this with the reaction of the normal eye, the physician confirms if the patient has Horner syndrome associated with nerve damage.

Additional tests are conducted to identify the location of nerve damage. One or more of the below tests may be required to detect the site of abnormality in the nerve:

Test type Purpose of the test
Magnetic resonance imaging (MRI) Produces detailed images of the inside of the nerves using radio waves and magnetic field
Computerized tomography (CT) Uses specialized imaging technology and X-rays to create images of required structures inside the body
X-rays Uses simple X-rays to generate images

In the case of children, blood tests may be required to diagnose the presence of tumors of the nervous or the endocrine system (hormonal system).