Horner syndrome


The face and eye on one side of the body may be impacted by Horner syndrome. The condition caused by a disturbance of the nerve pathway from the brain to the head and neck.

The sympathetic nerves that connect your brainstem to your eyes and face are disrupted, which causes it to happen. These nerves regulate involuntary functions, including sweating (perspiration) and the constriction and dilation of your eye pupils.

Horner syndrome frequently manifests as drooping eyelids, smaller pupils, and reduced facial perspiration on the affected side.

A stroke, tumor, spinal cord damage, or another medical condition may cause Horner syndrome. Sometimes there is no underlying reason for a problem. Horner syndrome doesn’t have a specific treatment, however addressing the underlying cause may help nerve function return.

Oculosympathetic palsy and Bernard-Horner syndrome are other names for Horner syndrome.


Only one side of the face is often affected by Horner syndrome. Typical warning signs and symptoms include:

  • Miosis or constricted pupil
  • A significant disparity between the size of the pupils in the two eyes (anisocoria)
  • The affected eye appears sunken.
  • Slow or delayed dilation of the afflicted pupil in low light
  • Ptosis where in the upper eyelids appear to drop
  • Upside-down ptosis, a slight elevation of the lower lid.
  • Little to no facial perspiration (anhidrosis) on the afflicted side

Ptosis and anhidrosis are two signs and symptoms that might be subtle and challenging to recognize.


Children with Horner syndrome may sometimes show additional symptoms like:

  • A child under the age of one with a lighter iris color in the afflicted eye
  • A change in hue on the side of the face that is being impacted, which is often brought on by heat, physical activity, or emotional responses.

Horner syndrome can be brought on by several things, some of which are more significant than others. Obtaining a timely and correct diagnosis is crucial.

Get immediate medical attention if Horner syndrome symptoms occur unexpectedly, follow a traumatic event, or are accompanied by other symptoms, such as:

  • Eyesight problem
  • Dizziness
  • Slurring of speech
  • Walking problem
  • Weakness or poor control of the muscles
  • A sudden or severe headache or neck pain


Damage to a specific sympathetic nervous system circuit results in Horner syndrome. The sympathetic nervous system controls your heart rate, breathing, sweating, blood pressure, and other bodily processes that let you react promptly to environmental changes.

There are three different types of nerve cells (neurons) along the nerve pathway that are impacted by Horner syndrome.

First-order neurons

The hypothalamus at the base of the brain serves as the starting point for this neuron pathway, which continues via the brainstem and into the upper part of spinal cord. Horner syndrome-related issues in this area that may impair nerve function include:

  • Tumor
  • Stroke
  • Conditions that result in the loss of neurons’ myelin sheaths
  • Syringomyelia or cyst growth in the spinal column
  • Trauma on the neck

Second-order neurons

From the spinal column, this neuron tract travels through the upper chest and into the side of the neck. The following factors could contribute to nerve injury in this area:

  • Having schwannoma or myelin sheath tumor
  • Malignancy in the lung
  • Surgical intervention in the chest
  • Impactful or traumatic injury
  • Damage to the aorta

Third-order neurons

Damage to this neural pathway, which runs alongside the neck, and leads to facial skin, muscles controlling the iris and the eyelids. Impairment in this area can be linked to the following conditions or symptoms:

  • Migraines
  • Cluster headaches
  • An injury to the carotid artery on the side of the neck
  • An injury to the jugular vein on the side of the neck
  • An infection or tumor close to the skull’s base


Children’s Horner syndrome is most frequently caused by:

  • Neck or shoulder injuries sustained during childbirth
  • Aortic anomaly present at birth
  • Neuroblastoma, a tumor of the neurological and hormonal systems.

Unknown causes

In some circumstances, it is impossible to determine what causes Horner syndrome. Idiopathic Horner syndrome is the term for this.