- Horner's syndrome appears when the three-neuron sympathetic pathway is interrupted anywhere from the posterior-lateral nuclei of the hypothalamus through the spinal cord to the eye. In children, Horner's syndrome can be either congenital or acquired, but overall it is a rare finding. There are several causes of Horner's syndrome, some of iatrogenic. Although uncommon in the paediatric population, prompt recognition of the syndrome and immediate treatment may prevent permanent damage to the neuronal pathway. Awareness of the risk of developing iatrogenic Horner's syndrome and early detection of signs are recommended to minimise future disability.