Horner’s syndrome Any condition or injury that destroys the sympathetic trunk ascending from the thorax through the neck into the face results in Horner’s syndrome, characterized by a drooping eyelid (ptosis), sunken globe (enophthalmos), narrow palpebral fissure, contracted pupil (meiosis), vasodilation and lack of thermal sweating (anhydrosis) on the affected side. Classically, this is seen in patients with bronchial carcinomas that have invaded the sympathetic trunk and is also a recognized complication of cervical sympathectomy or a radical neck dissection. Avulsion of the first thoracic nerve from the spinal cord may be diagnosed by development of the syndrome after closed traction lesion of the supraclavicular brachial plexus. Congenital Horner’s syndrome has been reported in association with ipsilateral internal carotid artery agenesis (Fons et al 2009). Special features of congenital Horner’s syndrome are iris heterochromia, a difference in colour between the two eyes that results from interference with melanocyte pigmentation of the iris by a lack of sympathetic stimulation during development, and unilateral straight hair.