Horner's syndrome

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at June 30, 2016
StartHorner's syndrome

Horner's syndrome, also known as Horner syndrome, oculosympathetic palsy or Horner-Bernard syndrome, is a relatively rare syndrome that affects the nerves that run from the brain to the eye. To date, Horner syndrome remains somewhat of a mystery to medical researchers. What is known is that prior history of certain diseases or traumas may lead to the later onset of Horner syndrome.


Definition & Facts

Horner syndrome is considered to be in the family of neurological disorders that affect the brain, spinal cord, and central nervous system of the body. Horner syndrome can strike anyone of any age, gender or ethnicity and affects females and males equally. The syndrome can arise all on its own, or it can be prompted by another pre-existing condition, disease, or trauma.

In some individuals, it is present from birth and is a congenital disorder. In these rarest of cases, it is termed "congenital Horner syndrome." If the syndrome presents before the individual has reached two years of age, the iris portion of each eye may be different colors. Horner syndrome is sufficiently rare that no statistics exist on incidence in the population today. 

Symptoms & Complaints

While the causes for Horner syndrome are many and varied, the symptoms are remarkably consistent from case to case. Commonly reported symptoms include the following:

  • Drooping eyelid (ptosis) on the side of the face that is affected.
  • Lack of sweating (anhidrosis) on the side of the face that is affected.
  • Decreased size in the pupil (miosis) of the eye that is affected.

These three symptoms, when occurring together, can accurately point to Horner syndrome. Sometimes the eyeball on the affected side will also sink further into the socket (orbit). In young children who have Horner syndrome, there may also be a noticeable paleness on the affected side of the face.


The causes for Horner syndrome can vary greatly. In some cases, Horner syndrome can occur on its own in an individual of any age. In other rarer cases, Horner syndrome is present at birth though the exact genetic mutations at play have not yet been identified. Inheritance appears to be autosomal dominant.

The underlying cause of Horner syndrome is nerve damage. The damage occurs in the nerves leading from the brain to one eye. There are three main groups of cells that exist along the nerve pathway that is affected by Horner syndrome. Sometimes physicians can extrapolate the cause of Horner syndrome by matching the triggering disease to the group of neurons that disease affects.

There are many pre-existing conditions or injuries that may either be risk factors for Horner syndrome or cause damage to one of the three neuron groups that can trigger the onset of Horner syndrome. Lesions of the first order (central) neurons may be caused by or linked to:

Lesions of the second-order neurons may be caused by or linked to:

Lesions of the third-order neurons may be caused by or linked to:

It is important to remember that, in some cases, it is not possible to determine the cause of Horner syndrome. These cases are called idiopathic. These cases are also different from congenital Horner syndrome.

Diagnosis & Tests

Diagnosing Horner syndrome begins with taking a thorough medical history of the patient and his or her family. The physician will look for any family history of Horner syndrome and also look for prior personal history of any of the diseases or injuries that have been linked to the onset of Horner syndrome. From here, the physician will catalog the chief symptoms before requesting and performing tests. Tests that are commonly done include the following:

Treatment & Therapy

At this time, there is no one uniform treatment or cure for Horner syndrome. Treatment focuses on resolving the condition(s) thought to be causing the symptoms of Horner syndrome. Surgery may be required for any aneurysms associated with Horner syndrome. If lung cancer is the culprit, treatment may incorporate chemotherapy and/or radiotherapy.

Sometimes, cosmetic surgery is recommended to correct the drooping eyelid on the side of the face affected by Horner syndrome. In some cases, no additional treatment is necessary. So long as the underlying condition can be successfully resolved, Horner syndrome will often resolve on its own.

Prevention & Prophylaxis

The only known way to prevent Horner syndrome is to prevent the onset of any one of the underlying conditions known to trigger Horner syndrome symptoms. The best method of prevention is to prevent trauma to the brain, neck, spine and chest, to forgo smoking and use of tobacco products and to maintain a healthy heart and lung function.

These preventative measures can help avoid the onset of Horner syndrome, but they are not a guarantee. Where there is no known cause for the onset of Horner syndrome, there is no prevention.