Horner’s Syndrome

Abstract

Homer’s syndrome is due to damage to the sympathetic pathway anywhere in its long course from the diencephalon down to the lateral gray in the upper thoracic spinal cord, and up again through the neck to the eye and upper eyelid. This pathway has three neurons. The central neuron passes from the hypothalamus through the posterolateral brain stem to the lateral gray in the spinal cord (Clarke’s column), ending at the level T1. The peripheral presynaptic neuron travels up the cervical sympathetic chain to end in its superior cervical ganglion. The peripheral postsynaptic neuron runs up on the surface of the carotid artery and branches off toward the eye at the level of the orbit to innervate the pupil, the upper eyelid, and the blood vessels of the eye, in particular those of the conjunctiva.