Horner's Syndrome

Horner's syndrome is an uncommon health condition in which nerve damage disrupts the brain's control over the eye. Although Horner's syndrome can occur in adults it usually occurs in infants as a result of a birth injury. Horner's syndrome is the result of damage to the nerve connections between the brain and the eyes.

The eyes and surrounding facial muscles are directly connected to the brain by delicate nerve fibers that run through channels going down either side of a person's face. The brain exercises control over the eyes by transmitting electrical signals across these facial nerve channels. Horner's syndrome (which is also known as "oculosympathetic palsy" or sometimes "Horner-Bernard syndrome") is unique disorder which occurs when one of these nerves on either side of the face is injured.

The damage to the nerve disrupts and distorts the normal communication between the brain and the eyes resulting in a very distinct collection of physical symptoms. Horner's syndrome almost always occurs on just one side of the face. The primary symptoms associated with Horner's syndrome are:

• Miosis: the pupil remains persistently small / contracted
• Anisocoria: pupils are not the same size in both eyes
• Ptosis: the upper eyelid remains droopy or dropped down
• Anhidrosis: absence of sweating on the affected side of the face

The affected eye may also have a somewhat sunken appearance in comparison to the other eye and the pupil will not expand in dim light conditions. In infants the eye affected by Horner's syndrome will often have a lighter color pigmentation that the other.

The biomechanics of Horner's syndrome are fairly well understood. Horner's syndrome is caused by injury or damage to one of the sympathetic nerves running down either side of the face. The brain uses these nerves to control the eyes so when one of the nerves is damaged it interferes with the brain's communication pathway to the eye. What is much more varied is the source of the injury to the nerve. Injury to the nerve can result from external physical trauma or from internal events such as a stroke or carotid artery damage.

Physical trauma to a baby's face during childbirth is the leading cause of facial nerve injuries resulting in Horner's syndrome. About 65% of all Horner's syndrome cases are connected to birth trauma. Facial nerve damage is one of the most common types of physical injury occurring during vaginal childbirth. When the baby is pushed head-first through the narrow birth canal the crown of the head and sides of the face are often subjected to significant pressure. The larger the baby and/or more narrow the birth canal the more significant this pressure will be. A prolonged labor will also increase the chance of facial nerve damage during delivery.

Another common source of trauma during childbirth that can damage facial nerves and caused Horner's syndrome is the use of birth assistance instruments. The primary birth assistance instruments used in modern delivery rooms are obstetrical forceps and vacuum extractor pumps. Forceps look like a large pair of salad tongs with spoon-like metal cups at the end. The cups are designed to fit around and grip the baby's head so that the doctor can maneuver them through the birth canal. Vacuum extractors have a special suction cup with a handle that attaches to a pump. The cup is fitted to the baby's head and the pump is used to create vacuum suction and seal the cup to the baby's head. Both of these tools, but particularly obstetrical forceps, can subject the baby's head and face to increased pressure and increase the potential for facial nerve damage.

A baby's pediatrician will typically make a diagnosis of Horner's syndrome based on a clinical examination alone. If symptoms of Horner's syndrome are noted in the exam the doctor may use special eye drops to dilate the baby's pupils. This allows the doctor to further confirm the diagnosis of Horner's syndrome by examining how the pupils respond to light. Diagnostic imaging tools such as an MRI are sometimes used to give doctors a picture of the damage to the facial nerve or pocket.

Treatment for Horner's syndrome is largely dependent on the underlying cause which triggers the condition. In adults Horner's syndrome may be caused by a number of health conditions which can be effectively treated. However, Horner's syndrome in infants is typically caused by birth trauma during vaginal delivery. The treatment options for Horner's syndrome resulting from birth trauma are much more limited. In some cases a baby's Horner's syndrome will go away on its own as the nerve injury gradually heals. In other cases Horner's syndrome can be more or less permanent if the damage to the facial nerve does not fully heal. Even with permanent damage to the nerve, however, the symptoms of Horner's syndrome will often fade as the baby gets older.

Whether permanent or short-term, Horner's syndrome is not really a serious health condition. However, Horner's syndrome is often an indication of more serious neurologic injuries suffered during childbirth.