Incomplete Horner syndrome: Report of a case and description of the sympathetic nervous system anatomy involved in Horner syndrome.

Horner syndrome, in which ptosis, miosis, and anhidrosis occur concomitantly, can arise from injury to the sympathetic nerve pathways anywhere from the brain to the end organs. Incomplete Horner syndrome lacks the sign of anhidrosis. We present a case of incomplete Horner syndrome caused by internal carotid artery dissection and provide a road map of the cervical sympathetic nerves involved in Horner syndrome to explain its etiology. We also discuss the imaging of and therapy for internal carotid artery dissections.