what causes horner's syndrome
Back to Top Causes. Horner syndrome can be caused by any interruption in a set of nerve fibers that start in the part of the brain called the hypothalamus and travel to the face and eyes. Sympathetic nerve fiber injuries can result from: 1  Injury to one of the main arteries to the brain (carotid artery).
Horner syndrome is caused by damage to a certain pathway in the sympathetic nervous system. The sympathetic nervous system regulates heart rate, pupil size, perspiration, blood pressure and other functions that enable you to respond quickly to changes in your environment.