Ultrasound is gaining in importance as a diagnostic method for rheumatic diseases such as giant cell arteritis. It can show thickenings of the intima media in detail and diagnose vasculitis with high sensitivity. Unlike the biopsy of the temporal artery, it is non-invasive, cheaper than an MRI, and more readily available in many places.
Researcher Valentin Schäfer has recently summarised the most important points on this subject in an overview analysis. Die to his work on the topic of ultrasound of joints and larger vessels in rheumatic diseases, he was also awarded the 2020 Rudolf Schoen Prize by the German Rheumatology Society (Deutschen Gesellschaft für Rheumatologie).
Giant cell arteritis, also called cranial arteritis or arteritis temporalis, belongs to the group of granulomatous vasculitis of large vessels and is the most common vascular inflammation in Germany.
It usually affects the arteries and branches of the external carotid artery. The eye vessels are involved in 40% of cases. The aorta, aortic arch, and the arteries of the upper and lower extremities are also involved in 40% of those affected.
Giant cell arteritis must be diagnosed as soon as possible in order to start treatment in time and avoid complications such as blindness. In addition to typical clinical practice and increased blood sedimentation rate, the biopsy is considered the gold standard in the diagnosis of vasculitis and is an integral part of the diagnostic criteria.
In the meantime, however, ultrasound is playing an increasingly important role, especially since it can detect inflammation of the temporal artery with high sensitivity. Thus, if the findings are clear and the clinic is suitable, it is already possible to dispense with the invasive biopsy, which must cover 20 mm (!) of the temporal artery and is often inconspicuous in the case of extracranial disease.
If giant cell arteritis is suspected, the temporal artery and the axillary artery should be assessed. Depending on the clinic and the findings, carotid arteries and facial vessels may be added. The sensitivity of the test increases with the number of vessels examined.
During sonography, intima-media thickness and flow velocities in the vessel are measured, among other things. Intima media values of 0.2 mm for the temporal artery and 0.6 mm for the axillary artery are considered normal for 70-year-old patients. The limit for pathological values is 0.4 mm and 1.0 mm respectively.
In the case of temporal arteritis, the ultrasound also shows a typical "halo" sign, a homogeneous, hypoechogenic wall thickening of the affected vessel. Classically, the thickened wall remains clearly visible under compression (compression sign).
While sonography is becoming increasingly important in the case of temporal arteritis, in the second granulomatous inflammation of the large vessels, Takayasu's arteritis, MRI remains the diagnostic method of choice.
PET-CT and CT also continue to be important for both vasculitis types in special cases. They can show the aorta and its branches well. Other new procedures include PET-MRI and contrast-enhancing ultrasound.
Ultrasound promises to be of great benefit in the diagnosis of giant cell arteritis and can be used extensively with appropriate training of the examiners. It remains to be seen whether it could also be used as a parameter for the course of the disease and the success of therapy in the future. Studies on this very issue are currently underway.
Sources:
1. Schäfer VS, Jin L, Schmidt WA. Imaging for Diagnosis, Monitoring, and Outcome Prediction of Large Vessel Vasculitides. Curr Rheumatol Rep. 2020 Sep 21;22(11):76. doi: 10.1007/s11926-020-00955-y. PMID: 32959107.
2. Press Release (Only in German): https://dgrh.de/Start/DGRh/Presse/Pressemitteilungen/Pressemitteilungen/2020/Pressemitteilung-Nr.-14-2020.html
3. Herold, Innere Medizin 2019 (Only in German)