There are many potential causes of Horner's Syndrome resulting from an interruption of the oculosympathetic pathway at any point between its origin in the hypothalamus and the eye. Cases have been reported resulting from head, neck and chest surgery, trajectory injury, and any neoplasm or infection affecting the oculosympathetic pathway. Horners syndrome is characterised by drooping eyelid, constriction of the pupil of the eye, and eyes that are unequal in size (Shuker, 2010). Moreover, it can include facial sweating and spasm (Shuker, 2010). Horner's syndrome can be confirmed and topographically (CT Scan) defined as involving a central, preganglionic, or postganglionic lesion through sequential pharmocologic testing. the importance of such localisation lies in differentiating neoplasia versus a benign condition such as congential Horner's as a cause of the syndrome. Topical cocaine (5 to 10 percent soultion) is used to confirm the presence of an actual Horner's syndrome. Two drops should be instilled in both eyes, by a qualified surgeon, every 5 minutes over a 30 minute period, after which time pupillary measurements are made. It is reported that individuals with Horner's Syndrome react poorly to cocaine, due to a increase in the amount of norepinephrine released at the neuromuscular junction, and thus an increase in the level of anisocoria (different sized pupils) is seen (Shuker, 2010).
Shuker, S.T. 2010. Horner's syndrome caused by penetrating AK47 assault rifle bullet neck injury. Journal of Oral Maxillafacial Surgery, 68, 2597-2601.