Look beyond the temporal arteries when using ultrasound to diagnose giant cell arteritis (GCA)
Ultrasound is very popular in Europe to diagnose GCA. Many centres have a specialised GCA ultrasound service and use it in preference to temporal artery biopsy. This practice was supported in the 2018 European (EULAR) guidelines for diagnosing GCA. The temporal arteries on the scalp are the most convenient and highest yield region for ultrasound and classically show a halo sign (artery wall is thickened and looks darker than the surrounding scalp) if a patient has GCA. Given that GCA affects a large number of medium and large arteries throughout the body, however, should we routinely look beyond the temporal arteries?
This paper by Hop et al. helps to answer this question in the affirmative – yes we do need to look beyond the temporal arteries. It was published on 2nd April 2020 and is from Groningen Hospital in the Netherlands. This hospital has been performing ultrasound of the temporal and axillary (armpit) arteries since 2013 for patients newly suspected of having GCA. The study found that ultrasound was more accurate when both the temporal and the axillary arteries were examined.
The most important finding was that 8 of the 41 patients with GCA (20%) had normal temporal arteries and the only ultrasound evidence of GCA in these patients was in the axillary arteries. Unfortunately, this centre did not routinely assess other arteries affected by GCA such as the vertebral, carotid, subclavian and occipital arteries so the additional benefit of including these could not be rigorously assessed.
Our current GCA ultrasound protocol incorporates the temporal and axillary arteries along with the occipital, carotid, vertebral and subclavian arteries. We believe this has the benefit of maximising the detection of GCA, providing a baseline assessment in case the disease progresses despite standard therapy, and identifying other vascular conditions which may mimic GCA including atherosclerosis.