Horner's syndrome consists of:
1) ptosis (droopy eyelid)
2) miosis (small pupil on the same eye where the eyelid is droopy)
3) anhidrosis (only some cases with lesions in specific anatomic sites)
It happens when there is damage to the sympathetic fibers (a type of nerve
fiber having to do with involuntary bodily functions including the size of
the pupil for example).
There are sympathetic fibers all along the thoracic spinal cord, brainstem
and up to a place called :hypothalamus" in the brain.
Also there are fibers of this type around the carotid artery (a large
artery in the neck that carries blood to the brain), forming like a very
Thus, lesions anywhere in these locations can produce a HORNER'S SYNDROME.
Did this help?