Congenital Horner’s Syndrome and Birth Trauma

Horner’s syndrome is characterized by certain facial asymmetries, mainly involving the eye. The affected eye will have an abnormally small pupil. It may also have a droopy upper lid and/or an elevated lower lid, and have a lighter colored iris than the other eye. Additionally, the affected side of the face may produce less sweat (1). Horner’s syndrome can be congenital (present at birth) or acquired later in life. Of congenital cases, most are caused by birth trauma (2).

Causes of Congenital Horner’s Syndrome

Although congenital Horner’s syndrome can occasionally be caused by vascular malformations or abnormal tissue growth such as a neuroblastoma, most cases are the result of traumatic birth injuries (2). Horner’s syndrome is associated with brachial plexus injuries, such as Klumpke’s palsy (1, 2).

Risk factors for Horner’s syndrome, birth trauma, and brachial plexus injuries include:

Medical professionals should be vigilant of warning signs that birth trauma may occur, and be prepared to intervene with measures such as an emergency C-section. Moreover, doctors must be very careful not to misuse labor-enhancing drugs, forceps, or vacuum extractors. Under very specific circumstances, these interventions can be beneficial, but there are also substantial risks involved. For example, in cases of true cephalopelvic disproportion, safe vaginal birth is impossible, so stronger contractions or pressure from birth-assisting tools will only cause harm.

Eye Anatomy

In order to really understand the ways in which Horner’s syndrome can affect an individual, it is important to know a bit of background information about the eye.

The iris, or colored part of the eye, is a circular muscle surrounding the pupil, which is a hole that enables light to enter the eye. A healthy pupil constricts (gets smaller) in a bright environment, and dilates (gets bigger) in a dark environment. Most people’s pupils dilate and constrict together; in other words, their right eye always looks the same as their left eye. Some people have anisocoria, which means that their pupils may be different sizes at the same time, because one pupil has difficulty responding to changes in light. Anisocoria is actually a relatively common condition, affecting approximately 20% of the population. People with anisocoria may have miosis or mydriasis:

  • Miosis: This means that the affected pupil is unable to dilate sufficiently. In darker environments, the difference between pupils will be more noticeable because the normal pupil will dilate (become larger), while the miotic pupil will remain small.
  • Mydriasis: This means that the affected pupil is unable to constrict sufficiently. In brighter environments, the difference between pupils will be more noticeable because the normal pupil will constrict (become smaller) while the mydriatic pupil will remain large.

Many cases of anisocoria are not associated with any serious medical conditions, and often the difference in pupil size is small enough not to be noticeable to a casual observer. Horner’s syndrome, however, may involve more obvious signs and symptoms.

Signs and Symptoms of Horner’s Syndrome

People with Horner’s syndrome may have the following signs and symptoms:

  • A miotic pupil, or one that appears to be abnormally small. The difference is more pronounced in darker environments
  • Ptosis (droopy upper lid) and/or inverse ptosis (elevated lower lid). Combined, these conditions make the eye itself appear smaller than it is. (It is important to note that if ptosis is on the side of the face with the larger pupil, this could be a sign of cranial nerve palsy, which is associated with serious medical conditions that require immediate attention.)
  • Heterochromia, which means that the iris of the affected eye appears lighter in color than the other iris
  • Lower pressure in the affected eye
  • Anhydrosis, or decreased sweating on the side of the face with the affected eye (1)
  • Redness on the affected side of the face

More serious symptoms include:

  • Dizziness
  • Vision issues
  • Severe headaches or neck pain
  • Weak muscles or a lack of muscle control (3)

Diagnosis of Horner’s syndrome

If Horner’s syndrome is suspected, doctors should refer the child to a pediatric opthamologist, who can evaluate their vision, how the pupils respond to different conditions, the position of the eyelids, and other variables.

Doctors should also look into underlying causes, such as potential birth trauma or signs of a neuroblastoma.

Management of Horner’s Syndrome

The focus of treatment is usually on addressing the underlying condition. For example, associated birth injuries such as Klumpke’s palsy may require certain medications or surgeries, as well as physical therapy. Likewise, neuroblastomas and other malignant tumors may require surgical removal, radiation, and chemotherapy (3, 4).

Horner’s Syndrome and Medical Malpractice

Congenital Horner’s syndrome is often the result of birth trauma, which in some cases could have been prevented had medical professionals followed standard of care. Standard of care is defined as what a reasonably prudent professional would do under similar circumstances. If you suspect your doctor may have failed to follow standard of care, and your child has Horner’s syndrome or associated conditions, a medical malpractice attorney may be able to help.

The malpractice attorneys at Reiter & Walsh ABC Law Centers focus exclusively on birth injury cases, and have decades of experience helping children and their families obtain the compensation they deserve. We can provide a free case evaluation to determine if your child suffered injuries due to the negligence of a physician or medical staff, and you never pay any money until we win your case. Please reach out to us today for more information:


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  1. Anisocoria and Horner’s Syndrome
  2. Incidence of Pediatric Horner Syndrome and the Risk of Neuroblastoma: A Population-Based Study
  3. What Is Horner’s Syndrome?
  4. Horner’s Syndrome