G90.2: Horner syndrome

The vertebrae form the vertebral canal on the rear of the spinal column. The spinal cord runs in the vertebral canal. Nerve fibers run from the brain via the spinal cord to the various parts of the body. Various processes in the body are controlled by the nerve fibers, for example.

Certain of your nerve fibers are damaged. These nerve fibers first run downwards from the brain to the spinal cord in the neck. Further forwards in the neck, the nerve fibers then run upwards again to the eyes. The nerve fibers ensure that you can open your eyes wide, for example. The nerve fibers also control the width of the pupils. For example, the pupils are narrowed in bright light, and widened in the dark.

Damage to these nerve fibers can result in you no longer being able to open your eye fully, for example. The eyeball may also look slightly sunken. Moreover, the pupil can no longer widen as much as it should, so it looks smaller. Depending on exactly where the nerve fibers are damaged, there can be other symptoms. For example, you may sweat less from the side of the face affected, or from your arm.

There are different causes behind the damage to these nerve fibers. For example, a tear in an artery in the neck may also damage the nerve fibers. Other causes can be circulatory disorders in the brain or tissue changes that get larger.