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Horner Syndrome

Medically reviewed by Last updated on Jan 5, 2023.

What is Horner syndrome?

Horner syndrome is a nerve condition that affects one side of your face. The condition is caused by an injury to a nerve that controls that side of the face. Horner syndrome may be a sign of a serious condition such as a stroke or aneurysm. It is important to seek immediate care if you develop other problems, such as head or neck pain.

What are the signs and symptoms of Horner syndrome?

  • Smaller pupil in one eye, and the pupil does not dilate (widen) well
  • Drooping upper eyelid, or a higher lower eyelid
  • Less sweating on one or both sides of your face or in a small area on one side
  • Redness on the white part of your eye

How is Horner syndrome diagnosed?

Your healthcare provider will examine your eyes and face. Your signs and symptoms may be enough for a diagnosis. Tell your healthcare provider about your symptoms, including when they began and if they have worsened over time. Tell the provider about your health conditions, such as cancer or a history of cluster headaches. The provider will also ask if you had any recent injuries. You may also need any of the following:

  • Eyedrops may be used to check how well your pupils dilate. The drops may make your affected pupil larger or your unaffected pupil smaller.
  • X-ray, CT, or MRI pictures may help your healthcare provider find the cause of the nerve damage, such as an injury or tumor. You may be given contrast liquid to help problems show up better in the pictures. Tell the healthcare provider if you have ever had an allergic reaction to contrast liquid. Do not enter the MRI room with anything metal. Metal can cause serious injury. Tell the healthcare provider if you have any metal in or on your body.

How is Horner syndrome managed?

Treatment of Horner syndrome depends on the cause. Signs and symptoms usually go away after the cause is treated. You may need any of the following:

  • An ophthalmologist (eye specialist) may be able to find and treat vision problems that develop.
  • Occupational therapy may be helpful if you have trouble seeing because of eyelid drooping. An occupational therapist can help you strengthen affected eye muscles. The therapist can also help you find ways to do your work or daily activities more easily if you are having vision problems.
  • Surgery or medication may be used if you have severe eyelid drooping.

When should I seek immediate care?

  • You have head or neck pain.
  • You have sudden vision changes or problems.
  • You are dizzy or weak.

When should I contact my healthcare provider?

  • You have new or worsening signs or symptoms.
  • You have questions or concerns about your condition or care.

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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