Isolated Horner's syndrome caused by intraoral gunshot

A 45-year-old man developed Horner's syndrome after sustaining an intraoral gunshot in a suicide attempt. Examination did not show any major vascular injury or other neurological symptoms. Radiograph of the skull and helical computed tomography angiography of the brain and neck detected a bullet embedded in the interior of the left internal carotid artery (ICA) sheath. Surgical examination showed an intact left ICA. Horner's syndrome resulting from intraoral trauma rarely presents as an isolated sign and is generally associated with carotid injuries. It may herald a life-threatening artery injury and needs urgent investigation.