Extended Color Doppler Ultrasound in the Diagnosis of Giant Cell Arteritis: Clinical Insights and Literature Review with Emphasis on Posterior Circulation Involvement

Background: Giant cell arteritis (GCA) is a systemic granulomatous vasculitis affecting large and medium-sized arteries, predominantly in individuals over 50 years. While it traditionally involves cranial branches of the external carotid artery, particularly the temporal arteries, growing evidence underscores frequent extracranial involvement, especially in the supra-aortic trunks. Objective: We aimed to critically review the diagnostic utility of extended Color Doppler Ultrasound (CDUS) in GCA, with a focus on vertebrobasilar involvement and current international imaging guidelines. Methods: Taking inspiration from a representative case of extracranial GCA with vertebrobasilar ischemic events, the current literature and international recommendations (e.g., EULAR, ACR, BSR and SIR) were reviewed. Results: Diagnostic accuracy significantly improves when CDUS is extended to include carotid, vertebral, subclavian and axillary arteries. Elevated inflammatory markers such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) correlate with large-vessel involvement and support the use of extended scanning protocols. International guidelines vary in their emphasis on extended CDUS, but consensus is growing toward ultrasound imaging-first strategies in expert hands. Conclusion: Extended CDUS is a sensitive, non-invasive first-line diagnostic tool for GCA. In patients with symptoms of the posterior cerebral circulation and elevated inflammatory indices, early comprehensive vascular imaging reduces diagnostic delay and may obviate the need for temporal artery biopsy.