In Horner's syndrome, on one side of the face, the eyelid droops, the pupil is small (constricted), and sweating is decreased. The cause is disruption of the nerve fibers that connect the eye and the brain.

• Horner's syndrome may occur on its own or result from a disorder that disrupts nerve fibers connecting the eyes and brain.
• The upper eyelid droops, the pupil remains small, and the affected side of the face may sweat less.
• Doctors test the pupil to see whether it can widen, and may do imaging tests to look for a cause.
• The cause, if identified, is treated.

Horner's syndrome can develop in people of any age.

Causes

Some of the nerve fibers that connect the eyes and brain take a circuitous route. From the brain, they go down the spinal cord. They exit the spinal cord in the chest, then go back up the neck beside the carotid artery, through the skull, and into the eye. If these nerve fibers are disrupted anywhere along their pathway, Horner's syndrome results. Horner's syndrome may occur on its own or be caused by another disorder. For example, it can be caused by disorders of the head, brain, neck, or spinal cord, such as lung cancer, other tumors, swollen lymph glands in the neck (cervical adenopathy), dissection of the aorta or carotid artery, a thoracic aortic aneurysm, and injuries. Horner's syndrome may be present at birth (congenital).

Symptoms

Horner's syndrome affects the eye on the same side as the disrupted nerve fibers. Symptoms include a drooping upper eyelid (ptosis) and a constricted pupil (miosis). The affected side of the face may sweat less than normal or not at all, and rarely, it appears flushed. In the congenital form, the iris of the affected eye remains blue-gray as it is at birth.

Diagnosis and Treatment

The disorder is suspected based on symptoms. To confirm the diagnosis, doctors may apply eye drops that contain small amounts of cocaine to the affected eye. If the pupil does not widen (dilate) after 30 minutes, Horner's syndrome is diagnosed. Doctors may apply other drugs to the eye later. How the pupil reacts to them indicates the general location of the damage. Magnetic resonance imaging (MRI) or computed tomography (CT) of the brain, spinal cord, chest, or neck is often needed to look for tumors and other serious disorders.

The cause, if identified, is treated. However, there is no specific treatment for Horner's syndrome. Often, no treatment is necessary because, typically, the eyelid only droops very slightly.

Last full review/revision November 2006 by Phillip Low, MD