Horner syndrome is a rare disorder that occurs when certain nerves that travel from your brain to your eyes and face are damaged.

Horner syndrome isn't a disease itself. Rather, it's a sign of another medical problem — such as a stroke, tumor or spinal cord injury. In some cases, however, no underlying cause can be found.

Horner syndrome usually affects only one side of your face. Typical symptoms of Horner syndrome include a drooping eyelid, decreased pupil size and decreased sweating on the affected side of your face.

There's no specific treatment for Horner syndrome. Instead, treatment is directed at the underlying cause, when possible.

Apr. 16, 2011