Lessons of the month: Giant cell arteritis with Horner's syndrome and vertebral dissection.

We present a case of an 82-year-old woman presenting with left-sided Horner's syndrome and stroke. She also had a 6-week history of intermittent dizziness, reduced appetite, lethargy, muscle stiffness and weight loss. Examination revealed left temporal artery and left posterior auricular artery tenderness. Her ESR showed 62 mm/hr and imaging showed left vertebral artery dissection. Temporal artery biopsy was positive.The case highlights a rare presentation of giant cell arteritis with Horner's syndrome and left vertebral artery dissection. High clinical suspicion is required to prevent delay in diagnosis and treatment.