Giant cell arteritis (GCA) should be suspected in patients 50 years and older with new onset of headaches. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels are often elevated in patients with GCA.¹ Temporal artery biopsy and vascular ultrasonography are two modalities that can be used to diagnose GCA. Ultrasonography of the temporal artery is the preferred method of diagnosis in Europe. Key findings that suggest GCA on ultrasonography include the halo sign (hypoechoic arterial wall thickening due to edema), the compression sign (inability of the technician to compress the lumen of the superficial temporal artery due to vessel wall inflammation), vessel stenosis, or total occlusion.² There is no standard cutoff for halo sign thickness that is universally considered diagnostic of GCA.³