Horner syndrome with transient visual impairment.

A 57-year-old female presented with headache, miosis, and ptosis diagnosed as Horner syndrome (HS). After delaying the recommended diagnostic imaging, she experienced transient, unilateral visual impairment in bright light. The patient was subsequently determined to have a spontaneous internal carotid artery dissection (ICAD) and secondary retinal ischemia with minimal cardiovascular risk factors and no history of preceding trauma. She wore dark glasses, received gabapentin for pain control, and was anticoagulated for a total of 4 months at which time the ICAD resolved despite a residual blepharoptosis and anisocoria.