Abstract 455: Using External Carotid Artery Injection in Digital Subtraction Angiography to Assist in the Diagnosis of Giant Cell Arteritis

Giant cell arteritis (GCA) is characterized by granulomatous inflammation of medium to large sized blood vessels. GCA is the most prevalent vasculitis, occurring in about 10 patients per 100,000 (1). Diagnosis remains challenging because biomarkers for this condition are not available. Current biomarkers, including elevated serum erythrocyte sedimentation rate (ESR) and C‐reactive protein (CRP), lack specificity (41.3%) and positive predictive value (29.3%) even in patients with disease confirmed with temporal artery biopsy (2). Invasive temporal artery biopsy typically performed under anesthesia itself has a sensitivity estimated to be 70‐90%, albeit a specificity around 99% (3). Other tests including temporal artery ultrasound and PET scans may be elucidating, though these are often nondiagnostic. Prompt identification and treatment is crucial in preventing permanent vision loss, aortic disease and rarely ischemic stroke. We describe a case of biopsy proven GCA initially identified with conventional DSA with selective injections of external carotid arteries. A 65‐year‐old female presented with sudden onset, severe headache with bilateral oculomotor palsy. The patients’ workup included CTA head and neck, MRI brain, orbits and cervical spine which were unremarkable. Initial serum testing including ESR, CRP were normal. Lumbar puncture was bland. The patient underwent digital subtraction angiography (to rule out intracranial pathology) which showed moderate tortuosity of bilateral external carotid artery branches (see figure 1A and 1B). She then underwent temporal artery biopsy which showed granulomatous inflammation consistent with giant cell arteritis. The patient was started on intravenous glucocorticoids and an oral prednisone taper and at follow up endorsed almost complete resolution of visual symptoms and headache. Given the limitations of standard methods in diagnosing GCA and morbidity associated with the disease, DSA with selective ECA injections should be considered in appropriate patients to obtain objective vessel characteristics and potentially aid surgeons in identifying optimal targets for biopsy.