Identical Horner Syndrome in Homozygotic Twins Caused by Non-Traumatic Internal Carotid Artery Dissection.

Internal carotid artery dissection is an uncommon entity and the result of a spontaneous or traumatic tear in the vessel lining. We present two almost identical cases of Horner syndrome caused by spontaneous, non-traumatic internal carotid artery dissection within 4 months in two 52-year-old homozygotic twin brothers.