Beyond the Headache: A Subtle Horner's Syndrome Revealing Carotid Artery Dissection.

Partial Horner's syndrome, characterized by ptosis and miosis without anhidrosis, is a classic but often underrecognized manifestation of internal carotid artery (ICA) dissection and may represent the sole clinical indicator of an evolving vascular pathology. Horner's syndrome is a neurological disorder caused by interruption of the sympathetic nerve pathways that supply the eye and face. Despite its clearly defined clinical features, Horner's syndrome is relatively uncommon, and standardized management guidelines are limited. Early detection relies on CT angiography (CTA), as the initial non-contrast CT can often be unremarkable. We report a 60-year-old male who presented with headache and features of partial Horner's syndrome, subsequently diagnosed with ICA dissection. This case highlights the need for clinicians to maintain a high index of suspicion for cervical artery dissection in patients presenting with unexplained Horner's syndrome, even in the absence of trauma or neurological deficit. Early recognition and urgent vascular imaging are essential for accurate diagnosis and prevention of potentially life-threatening complications.