Progressive visual loss in a patient with presumed temporal arteritis despite treatment: how to make the diagnosis.

Giant cell (temporal) arteritis is a severe potentially fatal systemic vasculitis characterized by focal involvement of the cranial arteries resulting in ischaemic arterial occlusion. The case is presented of a 75-year-old woman with presumed giant cell arteritis and normal bilateral temporal artery biopsies. Despite a seemingly adequate course of systemic steroid therapy, the patient developed sudden catastrophic vision loss. Cerebral angiography and ultrasonography were useful investigations to determine the most appropriate artery to biopsy to confirm the diagnosis of giant cell arteritis.