What is Horner's syndrome and what are its symptoms and causes?

What is Horner's syndrome and what are its symptoms and causes?
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Horner's syndrome is caused by damage to the nervous system and has typical manifestations. What causes it and how is it treated?

Most common symptoms

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Horner syndrome (also known as Claude-Bernard-Horner syndrome = CBH syndrome) is characterized by a triad of symptoms:

  • miosis (Latin for myosis), i.e., narrowing of the pupil.
  • ptosis of the eyelid (drooping)
  • apparent monophthalmos (eye sunken into the orbit)

It occurs when the sympathetic nervous system is disrupted, both at the level of central damage and at the preganglionic (oppression of the cervical sympathetic) and postganglionic (oppression in the plexus caroticus) levels.

Who discovered Horner's syndrome?

The first description of this disorder was published in 1727 by Francois Pourfour du Petit after an experimental nerve severance in a dog. Claude Bernard described it even more accurately in 1982. The definitive description came in 1869 from the Swiss ophthalmologist (eye disease physician) Johann Friedrich Horner.

What is Horner's syndrome?

Claude-Bernard-Horner syndrome is thus a type of peripheral autonomic syndrome that develops when there is a lesion of the superior cervical sympathetic nerve (segment C8-Th1 of Budge's ciliospinal centre - damage to the spinal roots, ramus communicans albus, ganglion cervicale craniale and plexus caroticus).

Simply put, it is a set of three symptoms that occur when the sympathetic nervous system in the neck is disturbed. The sympathetic nervous system is a set of nerves and nerve ganglia that regulate certain bodily functions and are independent of our will. The cervical sympathetic system controls the eye, among other various functions.

Clinically, it manifests itself

  • ptosis - drooping of the eyelid
  • miosis - narrowing of the pupil
  • Onophthalmia - an eye that is sunken into the orbit
  • hyperhidrosis - excessive sweating
  • hyperthermia - increased body temperature on the relevant side of the face.

Claude-Bernard-Horner syndrome can also develop when there is damage to the nuclei in the hypothalamus and brainstem, but then it is part of the pontine syndrome.


What can cause sympathetic damage and the development of Horner's syndrome?
What are its causes?

Horner's syndrome is caused by a number of different conditions, including sudden stroke, brain tumours or trauma. However, there is also a congenital form of Horner's syndrome in which the syndrome is present from birth.

Sometimes the cause of Horner's syndrome cannot even be determined.

The most common causes include...


A genetic disease that causes tumors to form from nerve tissue.

Neuralgia of the trigeminal nerve

Trigeminal nerve pain.

Inflammation of the spinal cord

And other diseases that cause damage to the protective coverings of neurons, so-called demyelinating diseases, such as sclerosis multiplex - multiple sclerosis.


Especially in the head and neck area.

Myasthenia gravis

Mutation of a gene responsible for the work of neuromuscular synapses.

Myasthenia gravis


Localized in the hypothalamus, spinal cord, brain, thyroid gland, larynx, lungs, nerve sheaths - so-called neurinomas or schwannomas and tumors of other structures of the neck, oral cavity or chest.


Or other pathological cavities of the spinal cord (syringomyelia).

Iatrogenic lesions

Damage to a patient caused by a doctor, for example, during surgery or cannulation of veins in the neck (central venous catheterisation), insertion of chemoports (to administer chemotherapy) or dialysis catheters.

Migraine pain

Recurrent attacks of intense, unilateral, throbbing headaches that are accompanied by nausea (feeling like vomiting), photophobia (lightheadedness), aura.

Migraine: what kind of headache is it, what are its causes, symptoms and treatment?

Frequent drinking of alcohol

And other types of intoxication.

Bleeding in the brain

As a result of a sudden stroke.

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Blockage or damage to blood vessels supplying the brain (a. carotis, a. vertebralis)

Causing an underblooded or impaired blood supply to the brain.

Damage to the large blood vessels leading out of the heart, aortic aneurysm

Life-threatening condition.

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An inflammatory process localized in the middle ear.

A tumor in the middle ear, a tumor caused by a tumor in the ear.

Most commonly of the heart, aorta, pulmonary artery and other vessels (coarctation of the aorta or tetralogy of Fallot).

Unknown causes

In some cases, the cause of Horner's syndrome cannot be identified. In this case, we speak of idiopathic Horner's syndrome.


Horner's syndrome usually affects only one half of the face.

The typical triad of symptoms appearing on the affected side is:

  1. narrowing of the pupil of the affected eye (miosis).
    • different pupil size in the two eyes (anisocoria)
    • the affected pupil does not dilate at all or insufficiently in the dark
  2. drooping of the upper eyelid
    • easy lifting of the lower eyelid on the affected eye (inverted ptosis)
  3. apparent slight retraction of the eye into the eye socket (enophthalmos)

Redness of the face on the affected side is also present, which is usually caused by dilated subcutaneous blood vessels.

Anhidrosis is also an accompanying symptom. It is a condition in which the affected person is unable to produce sweat or produces sweat at a reduced rate (hypohidrosis).

It is particularly dangerous when the body temperature is elevated. Hyperpyrexia (fever above 40 °C) may occur as a result of the body's inability to cool itself.

This condition also occurs, for example, during physical activity and being in a warm environment.

Another symptom is the ciliospinal reflex and transient hyperemia (bloodshot) of the conjunctivae.

Some of the symptoms, especially ptosis and anhidrosis, may be very mild. In this case, they are very difficult to detect.

In addition, children with Horner's syndrome may still have the following symptoms:

  • lighter iris colour in the affected eye in children under one year of age
  • the affected half of the face is not red when in a warm room, during physical exertion or as part of an emotional reaction, as in a healthy person


When to see a doctor? How is Horner's syndrome diagnosed?

Horner's syndrome can be caused by both serious and minor illnesses. Therefore, it is important to see a doctor as soon as possible and not to delay your visit unnecessarily.

If you develop any of the above symptoms of Horner's syndrome, you should seek medical attention immediately.

However, if any of the following symptoms appear, it is better to call the emergency medical services:

  • sudden deterioration or loss of vision, including blurred vision
  • dizziness, nausea or vomiting
  • muscle weakness or inability to control muscles
  • sudden onset of severe headache or neck pain
  • photophobia (increased sensitivity to light)

A person with Horner's syndrome should be examined by an ophthalmologist and a neurologist.

The latter will then refer the sufferer for an examination:

  • CT scan (computed tomography) or MRI to rule out brain disease.
  • an ultrasound scan (also called a sonogram or ultrasound) of the neck to rule out oppression of the nervous structures

Pharmacological tests:

  • cocaine test
  • hydroxyamphetamine test
  • phenylephrine test


The complex triad of symptoms is easily recognizable.

In patients with Horner's syndrome, the damaged pupil is proportionally smaller than the intact pupil. The eyelid droops and can only be lifted with minimal force.

In response to light, the pupil dilates slowly and usually incompletely in Horner's syndrome.

The physical damage affects only the eye and the eye muscles. For example, as a result of the constriction of the pupil, the perceptual behaviour of the eye may change in a negative way. The field of vision is reduced as a result of the drooping eyelid and three-dimensional vision may be severely impaired.

Sufferers may suffer from psychological distress as their facial expression may change significantly as a result of the symptomatic triad.

Horner's syndrome in dogs

Interestingly, this syndrome also affects dogs, especially the Golden Retriever breed.

It is most commonly caused by a severe ear infection. This can affect any of the fibres that are responsible for transmitting nerve impulses to the muscles of the face.

It can also be caused by a bite, where the nerves can be damaged.

There are several distinguishing features of Horner's syndrome in dogs. Usually all these symptoms occur on the same side of the body.

  • Slightly drooping upper eyelid
  • An eye ball that appears to be slightly sunken into the eye socket
  • A protruding eyelid that partially covers the side of the eye closest to the nose
  • One pupil is smaller than the pupil in the other eye and does not dilate fully in dim/dark lighting
  • Rarely, the affected side may be warmer to the touch and the skin may appear "pink" compared to the unaffected side.

Prevention of occurrence is by strict ear hygiene and avoidance of contact with another dog in which a bite might occur.

How it is treated: Horner's syndrome

Horner's syndrome and its treatment

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Interesting resources

  • Gašparec P, Köppl J, Tomová Z. Vascular accesses. Osveta: Martin, 2009: 240.
  • Kusminski RE. Complications of Central Venous Catheterization. J Am Coll Surg, 2007; 204: 681-696.
  • Best AE. Pourfour Du Petit´s experiments on the origin of the sympathetic nerve. Med Hist, 1969; 13: 154-174.
  • Georgie A, Haydar AA, Adams WM. Imaging of Horner's syndrome. Clinical Radiology 2008; 63: 499-505.
  • Suominen PK, Korhonen AM, Vaida SJ. Horner´s syndrome secondary to internal jugular venous cannulation. Journal of Clinical Anesthesia, 2008; 20: 304-306.
  • pediatriepropraxi.cz - Claude Bernardov - Horner's syndrome after catheterization of the vena jugularis interna
  • mayoclinic.org - Horner's syndrome in English