Horner Syndrome

Medically Reviewed by Zilpah Sheikh, MD on March 12, 2024
Written by Susan Bernstein, Alicia Garceau, Amy Gopal
5 min read

Horner syndrome is a rare condition that causes problems with your face and eye on one side of your body. It's also called Horner-Bernard syndrome or oculosympathetic palsy.

The condition is neurological, meaning it’s linked to your body’s nervous system. Certain nerves related to involuntary body functions (like how your eye’s pupils dilate or constrict) are affected.

You can get Horner syndrome at any age. In rare cases -- about 1 in 6,250 births -- a baby will be born with it.

A key sign of Horner syndrome is when the following symptoms affect just one side of your face:

  • Less or no sweat on one side of your face
  • A droopy upper eyelid (ptosis)
  • A lower eyelid that’s slightly raised (inverse ptosis)
  • A small pupil, the black circle in the middle of your eye (miosis)
  • Pupils that are of different sizes (anisocoria)
  • A pupil that doesn’t open (dilate) widely or is slow to open in dim light
  • A sunken or bloodshot eye

You may have additional symptoms depending on the cause of your condition.

Horner syndrome alone isn’t life-threatening, but it can be a sign of a serious health condition. See your doctor if you notice any of its symptoms.

Symptoms of Horner syndrome in children

Children who get Horner syndrome also can have:

  • One iris (the colored circle around the pupil) that's lighter in color than the other (heterochromia iridis). This usually occurs in children under 2 years.
  • A change of color on one side of their face that would normally happen in response to heat, physical exertion, or emotional reactions such as being angry, embarrassed, or upset.

Horner syndrome happens when a specific group of nerves (called a pathway) is damaged. Pathways are part of your sympathetic nervous system, which controls things such as your heart rate and blood pressure. It also controls your ability to sweat and how your pupils get bigger or smaller in response to light. If you have Horner syndrome, one of three different pathways may be involved:

First order (central)

This pathway involves the nerves that run from the hypothalamus in your brain to your chest, through your brain stem and spinal cord. Conditions that can affect it include:

  • Sudden interruption of blood flow to your brain stem
  • Tumors on your hypothalamus
  • Spinal cord lesions
  • Stroke
  • Damage to myelin (a thin sheath around your nerves)

Second order (preganglionic)

These nerves go from your chest to the top of your lungs and along the carotid artery in your neck. They might be affected by:

  • Tumors in your upper lung or chest
  • Injury or surgery involving your neck or chest

Third order (postganglionic)

This path runs from your neck to your middle ear and eye. Things that can affect it include:

  • Carotid artery lesions
  • Middle ear infections
  • Injury to the base of your skull
  • Migraine or cluster headaches

In about 35%-40% of cases, doctors aren’t sure what exactly causes Horner syndrome. Some researchers think it can be tied to your genes, but no specific genes have been linked to it yet.

Horner syndrome causes in children

Neuroblastoma, a type of cancer, can cause Horner syndrome in some kids. It's called congenital Horner syndrome when a baby is born with it. Only 5% of cases are congenital.

Babies can get Horner syndrome from neck or shoulder injuries during birth. Those born with damage to their aorta, or a lack of development (agenesis) of the carotid artery, can also have it.

In extremely rare cases, mutated genes from one parent can cause a baby to have a congenital form of the condition.

Your regular doctor or an eye doctor (ophthalmologist) can do tests to check for Horner syndrome.

They’ll do a physical exam and ask about your medical history to find out if you've had any illness or injury that could have caused nerve damage. Then, they’ll put drops in your eyes to see how your pupils react.

Other tests may show a growth, damage, or injury that could cause Horner syndrome. The doctor might order one or more of these imaging tests:

  • X-rays
  • MRI: Powerful magnets and radio waves make detailed images.
  • CT scan: Several X-rays from different angles are put together to show a more complete picture.
  • Carotid ultrasound: Sound waves make an image of your carotid artery.

Your doctor also may want to test your blood or urine to check for any health problems that could cause nerve damage.

There aren’t any treatments specifically for Horner syndrome. The best way to ease your symptoms is to treat the health problem that caused it. 

For example, if you have a tumor or lesion, your doctor might remove it through surgery. You could also have radiation and chemotherapy.

Certain symptoms, such as ptosis, can be corrected with cosmetic surgery or eye drops.

Often, Horner syndrome happens because of another health problem, so there’s no way to prevent it.

To avoid getting the condition from an injury, don’t take unnecessary risks that could result in an accident.

Nerve damage causes Horner’s syndrome, and it can happen at any age. If you have symptoms such as no sweating, a droopy eyelid, or problems with your pupil on one side of your face, you should talk to your doctor. With a diagnosis, you can learn how to manage the condition.

Is Horner syndrome life-threatening?

No, but it can be a sign of another serious health problem, so it's important to talk to your doctor about your symptoms.

How do you fix Horner syndrome?

There is no specific treatment for Horner syndrome. Symptoms usually improve when the condition that is causing it is treated.

Which cranial nerve causes Horner syndrome?

There are three groups of nerves, or pathways, that may be damaged and can cause Horner syndrome. They include:

  • First order (central)
  • Second order (preganglionic)
  • Third order (postganglionic)