Acquired infantile Horner syndrome and spontaneous internal carotid artery dissection: a case report and review of literature.

Horner syndrome, a triad of ptosis, anisocoria, and anhidrosis, results from interruption in the oculosympathetic pathway. It is classically described as either congenital or acquired to depict its underlying pathophysiology and requisite work-up. We report a case of a 10-month-old infant presenting with an acute onset of left Horner syndrome secondary to a spontaneous extracranial internal carotid artery dissection. To the best of our knowledge, this is the first case report in the literature of acute onset of acquired infantile Horner syndrome in association with spontaneous carotid artery dissection confirmed with magnetic resonance angiogram.