In what instances might a diagnosis of Giant Cell Arteritis be supported by radiography or nuclear medicine studies?
Giant Cell Arteritis patients presenting with aortitis and large-vessel involvement alone typically do not have cranial symptoms and have a negative temporal artery biopsy in up to 40% cases. In this clinical situation, characteristic MRI/MRA, FDG-PET, or CTA findings are adequate to confirm a diagnosis of GCA. Recent EULAR recommendations suggest early imaging in all GCA patients when available using MRI/MRA, CT, and/or FDG-PET as the preferred modalities in evaluating aortitis and large-vessel predominant GCA. High-resolution MRI may also be reasonable as an initial diagnostic study for evaluating predominantly cranial GCA if ultrasound is unavailable. Fig. 27.1 outlines the use of these studies in the diagnosis of GCA.