Horner Syndrome: A Clinical Review.

Horner syndrome results from an interruption of the oculosympathetic pathway. Patients with Horner syndrome present with a slightly droopy upper lid and a smaller pupil on the affected side; less commonly, there is a deficiency of sweating over the brow or face on the affected side. This condition does not usually cause vision problems or other significant symptoms, but is important as a warning sign that the oculosympathetic pathway has been interrupted, potentially with serious and even life-threatening processes. The oculosympathetic pathway has a long and circuitous course, beginning in the brain and traveling down the spinal cord to exit in the chest, then up the neck and into the orbit. Therefore, this syndrome with unimpressive clinical findings and insignificant symptoms may be a sign of serious pathology in the head, chest, or neck. This clinical review discusses how to identify the signs, confirm the diagnosis, and evaluate the many causes of Horner syndrome.