Giant cell arteritis

Last revised by Arlene Campos on 13 Jun 2024

Giant cell arteritis (GCA) is a common granulomatous vasculitis affecting medium to large-sized arteries. It is also known as temporal arteritis or cranial arteritis, given its propensity to involve the extracranial external carotid artery branches such as the superficial temporal artery. Although temporal artery biopsy (TAB) is the gold standard in diagnosis of giant cell arteritis, imaging is increasingly playing a role in non-invasive evaluation.

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Giant cell arteritis is the most common primary systemic vasculitis. It has an incidence of 200 per million persons per year 6. It typically affects older individuals with patients usually being older than 50 years, with a peak incidence between the ages of 70 and 80 years 3. There is a recognized female predilection 17.

There are many possible clinical features that present subacutely 10,25:

It is histologically similar to other large vessel vasculitides (such as Takayasu arteritis) showing granulomatous inflammation of arteries with infiltration predominantly by histiocytes, lymphocytes, and multinucleated giant cells. The characteristic multinucleated giant cells are only found in ~50% of cases 1.

Areas of normal superficial temporal artery interspersed within inflamed sections of artery, known as skip lesions, result in false negatives in up to 8-28% of cases 12,13,15.

In a study of 285 patients with biopsy-proven giant cell arteritis there were four main histological patterns 12:

  1. adventitial pattern: inflammatory cells restricted to the adventitia

  2. adventitial invasive pattern: local invasion of the media with preservation of the intima

  3. concentric bilayer pattern: inflammatory infiltration of adventitia and intima with preservation of the media

  4. panarteritic pattern: inflammatory infiltrates in the three arterial layers

Can potentially affect any medium to large-sized vessels. Vessel involvement can be broadly dichotomised into two overlapping phenotypes 27:

  • cranial giant cell arteritis (C-GCA): classic clinical presentation, particular involvement of the extracranial branches of the external carotid artery, more likely to have a positive temporal artery biopsy 6,27

  • large vessel giant cell arteritis (LV-GCA): more likely to have an atypical presentation (e.g. more constitutional symptoms), particular involvement of the aorta and its major branches, less likely to have a positive temporal artery biopsy 7,27

  • increased diameter and hypoechoic wall thickening (halo sign) of the superficial temporal artery (and/or other imaged arteries, e.g. vertebral artery 20, axillary artery 21)

    • with duplex ultrasound of the superficial temporal artery, sensitivity is 87% and specificity is 96% 9

    • more specific for giant cell arteritis if bilateral 8

    • reversible under corticosteroid treatment; this is reflected in the normalization of the sonographic features

  • stenosis may be present but is not a specific sign for giant cell arteritis 8

CT may be normal and is inferior to MRI in the diagnostic work-up of giant cell arteritis. Abnormal findings on CT are non-specific and may include:

  • wall thickening of affected arterial segments

  • calcification

  • mural thrombi

Arterial phase CT (angiography) may be useful for assessing luminal abnormalities:

  • stenoses

  • occlusions

  • dilatations

  • aneurysm formation

MRI brain with MR vessel wall imaging has a very high negative predictive value in evaluating giant cell arteritis 2, indeed it has been suggested in one study to obviate the need for temporal artery biopsy if the MRI is normal 24. MR vessel wall imaging should be interpreted alongside time of flight angiography to ensure the correct vessels, namely the superficial temporal arteries, are being reviewed.

On MR vessel wall imaging, giant cell arteritis is characterized by mural inflammation in the superficial temporal arteries, best seen on T1 C+ (Gd) sequences, whereby there is mural enhancement and thickening 2. This can be graded as either physiologic (grades 0 and 1) or pathologically indicative of mural inflammation (grades 2 or 3) 2:

  • grade 0: no mural thickening (<0.5 mm) and no mural contrast enhancement

  • grade 1: no mural thickening (<0.5 mm) and only slight mural contrast enhancement

  • grade 2: mural thickening (>0.6 mm) and prominent mural contrast enhancement

  • grade 3: strong mural thickening (>0.7 mm) and strong mural contrast enhancement

Additionally, MRI brain may demonstrate:

  • mural involvement, indicating arteritis, of other arteries

  • complications of mural involvement, e.g. stenoses, occlusions, dilatations, aneurysm formation, ischemic stroke

  • enhancement of the temporalis muscle: seen in ~20% of cases 22

  • orbital inflammation, e.g. optic perineuritis, orbital apex inflammation 23

18F-FDG PET/CT shows vascular 18F-FDG uptake in affected arteries, particularly affected large vessels 26,27. According to one study, the most common arteries where this uptake is demonstrated include 26:

There may also be concurrent uptake in a pattern consistent with polymyalgia rheumatica, such as within the shoulders and hips 28.

Treatment is primarily with immunosuppression. Agents that may be used include 11,14,17,18:

  • corticosteroids (e.g. prednisolone)

  • tocilizumab (interleukin-6 inhibitor)

  • methotrexate

  • secukinumab (interleukin-17 inhibitor)

Aspirin is often used adjunctively for prevention of ischemic events 19.

Imaging differential considerations include:

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