Horner syndrome also known as Horner-Bernard syndrome or oculosympathetic palsy is a combination of symptoms caused by an obstruction of a nerve pathway from the brain to the face and eye on one side of the body.

General signs of Horner syndrome include decreased pupil size, drooping eyelid and reduced sweating on the affected side of the face.

Horner syndrome can result from a stroke, tumor or spinal cord injury. Some cases reveal no underlying condition. There is no particular treatment for Horner syndrome but treatment of the underlying condition can sometimes restore nerve function.



Signs and symptoms of Horner syndrome include:


  • Persistently small pupil (miosis)
  • Considerable difference in pupil size between the two eyes (anisocoria)
  • Little or delayed opening (dilation) of the affected pupil in dim light
  • Drooping of the eyelid (ptosis)
  • Little or no sweating (anhidrosis) on the entire side of the face or an isolated area of skin on the affected side


Symptoms of Horner syndrome in children include:


  • Lighter iris color in the affected eye (affects children under the age of 11)
  • Lack of redness (flushing) on the affected side of the face that usually occurs from heat, physical exertion or emotional reactions.



Horner syndrome is a result of damage to a certain pathway in the sympathetic nervous system. The sympathetic nervous system regulates hart rate, perspiration, blood pressure, pupil dilation and other reactions typical to changes in the environment.

The nerve pathway that is damaged due to Horner syndrome can be divided into 3 groups of nerve cells (neurons):


First-order neurons

This pathway ranges from the hypothalamus at the base of the brain through the brainstem and into the upper part of the spinal cord. Conditions specific to that region that can interrupt nerve function include:


  • Stroke
  • Tumor
  • Neck trauma
  • Cyst or cavity in the spinal column (syringomyelia)
  • Diseases that destroy the protective sheath on neurons (myelin)


Second-order neurons

The second-order neurons extend from the spinal column across the upper chest and into the side of the neck. Conditions that can cause nerve damage in this area include:


  • Lung cancer
  • Tumor of the myelin sheath (schwannoma)
  • Damage to the aorta
  • Traumatic injury
  • Surgery in the chest cavity


Third-order neurons

The third area of the nerve pathway extends along the side of the neck leading to the facial skin and muscles of the iris and eyelids. Conditions that can affect this region and cause nerve damage include:


  • Damage to the carotid artery (located along side of the neck)
  • Damage to the jugular vein (located along side of the neck)
  • Tumor or infection near the base of the skull
  • Migraines
  • Cluster headaches (cyclical patterns of severe headaches)



The most common conditions that cause Horner syndrome in children include:


  • Defect of the aorta at birth
  • Injury to the neck or shoulders during delivery
  • Tumor of the hormonal and nervous systems (neuroblastoma)


Finally, in rare cases the cause of Horner syndrome cannot be determined. This is called idiopathic Horner syndrome.