Horner syndrome.

Horner syndrome refers to the constellation of signs resulting from the interruption of sympathetic innervation to the eye and ocular adnexae. Classically, the clinical findings include a triad of ipsilateral blepharoptosis, pupillary miosis, and facial anhidrosis. The history, additional clinical examination features, and pharmacologic testing may help localize the lesion and suggest an etiology. An appropriate evaluation of Horner syndrome and a timely elucidation of the etiology may allow for a potentially life-saving intervention.