Giant cell arteritis (GCA) is a primary vasculitis that affects especially extracranial medium-sized arteries, such as superficial temporal arteries (TAs). Three findings are important for the ultrasound (US) diagnosis of TA: „dark halo” sign, which represents vessel wall edema, stenosis, and acute occlusions. US has a high sensitivity to detect vessel wall thickening in the case of large vessels GCA. The eye involvement in GCA is frequent and consists in arteritic anterior ischemic optic neuropathies or central retinal arterial occlusion, with abrupt, painless, and severe loss of vision of the involved eye. Because findings of TAs US do not correlate with eye complications in GCA, color Doppler imaging of the orbital vessels is of critical importance (it reveals low end diastolic velocities, and high resistance index), in order to quickly differentiate the mechanism of eye involvement (arteritic, versus non-arteritic). The former should be treated promptly with systemic corticosteroids to prevent further visual loss of the fellow eye.
Clues to the pathogenesis of giant cell arteritis from the study of the vessel wall