DWI scalp dot sign: superficial temporal artery restricted diffusion in giant cell arteritis.

Abstract

Dear Editor, We would like to report a novel finding on standard diffusion-weighted magnetic resonance imaging (DWI-MRI) in a case series of four patients with giant cell arteritis (GCA) in the superficial temporal artery (STA). GCA is considered a clinical emergency and is the most common vasculitis in adults, which, if untreated, can rapidly cause irreversible sight loss and ischaemic stroke [1]. Unfortunately, clinical presentation is variable and classic symptoms such as headache and scalp tenderness can be absent, delaying diagnosis and therapy [1]. Temporal artery biopsy (TAB) is considered the reference standard for diagnosis, but sensitivity can be as low as 40% due to skip lesions and inadequate specimens [2]. The European Alliance of Associations for Rheumatology recommends temporal and axillary artery ultrasound (US) as a first-line investigation in patients suspected of having GCA [3]. The finding of an arterial halo on US, reflecting inflammatory oedema of the arterial wall, is thought diagnostic for GCA with a specificity of 96% [4]. However, the sensitivity of US is lower (43–77%) and is highly technique and operator dependent [4, 5]. In both TAB and US, sensitivity drops further if performed after commencing steroid therapy. Post-contrast vessel wall magnetic resonance imaging (VW-MRI) has been proposed as a potential alternative first-line imaging investigation, with experienced units reporting a sensitivity of 80% and a specificity of 100% [5]. VW-MRI is still a relatively new technique and not yet readily available.