Ultrasound in the diagnosis and management of giant cell arteritis (GCA)

David Goldemund M.D.
Updated on 22/10/2024, published on 22/10/2024

in the acute GCA, ultrasound shows a non-compressible, hypoechoic wall thickening of the temporal and other arteries
reliability is excellent and comparable to biopsy
ultrasound should be used as a first-line diagnostic test for patients with suspected GCA; rapid examination and initiation of therapy reduce the risk of permanent vision loss

permanent vision loss due to anterior ischemic optic neuropathy is a serious complication of GCA, occurring mainly in untreated patients ⇒ prompt diagnosis and treatment are thus crucial
glucocorticoid therapy should be started immediately
ultrasound (US) is a safe, inexpensive, and readily available diagnostic tool with characteristic findings in both GCA and Takayasu arteritis
immediate US examination has 2 advantages:
- physicians performing both clinical and ultrasound exams can provide instantaneous diagnosis and treatment, reducing the risk of delayed treatment or unnecessary glucocorticoid use.
- rapid ultrasound visualizes pathologic changes before treatment alters their appearance (the visibility of the halo sign decreases rapidly after 2-3 days of treatment) (Schmidt, 2018)
- delayed US may yield false-negative results
temporal artery biopsy may remain positive for weeks

imaging should be performed by specialists with appropriate equipment (> 300 US examinations are required).
modern high-resolution linear probes with Doppler mode should be used, especially for temporal artery studies
US resolution increases with higher frequencies, and tissue penetration increases with lower frequencies
probes with ≥ 15MHz frequency should be used to detect minor wall thickening.
- probes with frequencies >20MHz are increasingly available, and such probes allow visualization of the normal intima-media complex of the temporal arteries

a normal arterial intima-media complex appears on ultrasound as a homogeneous, hypo- or anechoic structure bounded by two parallel hyperechoic margins
the following pathological features may be seen on the US in patients with GCA:
- hypoechoic wall thickening (halo sign)
  - high-frequency probe is required (≥ 15-20 MHz)
  - edema/fluid is black
  - the cut-off for the common superficial temporal artery 0.42 mm, frontal branch 0.34 mm, parietal branch 0.29 mm, and axillary artery 1.0 mm (Schäfer, 2017)
- non-compressible arteries
  - a positive compression sign is defined as the visibility of the TA during transducer-imposed compression of the artery (Aschwanden, 2013)
- lumen stenosis (turbulent flow, increased velocity) or occlusion (absence of Doppler signal)
  - stenosis should be considered only to assess the severity of damage and not to confirm the diagnosis of GCA

temporal and axillary arteries (routinely examined in suspected GCA)
- routine examination of the axillary arteries is essential in suspected GCA cases, as temporal arteries may be spared in 40% of cases
- superficial temporal arteries should be scanned in both longitudinal and transverse planes + frontal and parietal branches
- axillary arteries are commonly involved in younger, predominantly female patients
occipital and facial arteries
- facial arteries wind around the body of the mandible; occipital arteries are located behind the ear
- involved in 30-40% of GCA patients
- facial arteritis causes more often jaw claudication and blindness
carotid arteries – CCA is more often involved than ICA and ECA; arteriosclerosis and vasculitis can be difficult to differentiate
- arteriosclerosis is characterized by heterogeneous (sometimes hyperechoic), irregular, and eccentric changes int he vessel wall
subclavian and vertebral arteries
- reversed flow in the VA indicates high-grade subclavian stenosis (subclavian steal phenomenon)
- subclavian arteries are insonated from above and below the clavicle
aorta
- the lungs interfere with examination of the thoracic aorta
- only part of the ascending aorta and the arch can be examined with low-frequency probes
- transesophageal echocardiography providing high-resolution images of the thoracic aorta is not routinely used
- CTA or MRA are preferred in this indication

axillary artery imaging is typically performed in the axilla
the patient’s arm is abducted and externally rotated to expose the axilla
for a transverse view, the probe is placed perpendicular to the artery, visualizing a cross-section of the vessel
for a longitudinal view, the probe is aligned parallel to the artery, providing a longitudinal view of the vessel
the axillary artery should be differentiated from:
- the axillary vein (which is typically more compressible and larger)
- lymph nodes
- brachial plexus
- muscles (such as the pectoralis major and minor)

ultrasound – when performed by experienced staff, along with clinical examination, can confirm or exclude a suspected diagnosis of GCA in most patients
US vs. biopsy
- temporal artery biopsy (TAB) may be necessary when US results are unclear, especially in those on long-term glucocorticoid treatment
- US-guided TAB does not significantly increase sensitivity over standard TAB
- US is faster and less expensive than TAB, reducing costs and waiting time
- TAB is less sensitive because it covers a limited area, whereas the US covers more regions in generalized disease
US vs. MRI/CT/PET
- MRI, CT, and PET are better for visualizing large vessels such as the thoracic aorta but they are expensive and involve radiation ⇒ US is a better choice for most patients unless there is suspicion of aortic involvement

with treatment, the halo becomes brighter, and its diameter decreases
- it may resolve within days to months after treatment is initiated (Hauhenstein,2012)
- residual wall thickening may remain visible for years, particularly in patients with temporal artery halo or occlusion
- in extracranial arteries (CCA, axillary artery), wall thickening usually remains visible for months or years
ultrasound monitoring might become more important in the future with treatments involving IL-6
- inhibition may reduce the usefulness of CRP and ESR measurements
wall thickness can be checked twice a year; increasing thickness suggests undertreatment
newer techniques may visualize other markers of disease activity, such as neovascularization on contrast-enhanced US