Giant cell arteritis (GCA) (plural: arteritides) 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.
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Epidemiology
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.
Associations
polymyalgia rheumatica: seen in ~50% of cases
Clinical presentation
There are many possible clinical features that present subacutely 10:
headache (most common clinical feature) with or without scalp tenderness
systemic symptoms (e.g. fever, fatigue, weight loss)
jaw claudication
transient vision loss (amaurosis fugax)
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permanent vision loss (e.g. due to anterior ischemic optic neuropathy, central retinal artery occlusion, ischemic stroke, etc.)
in such cases, there may be accompanying Charles-Bonnet syndrome
weak pulse over affected arteries
bruits on auscultation over the affected arteries
clinical features of an aortic aneurysm or dissection if the aorta is involved
Markers
serum erythrocyte sedimentation rate (ESR): markedly raised
serum C-reactive protein (CRP): often markedly raised
Pathology
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:
adventitial pattern: inflammatory cells restricted to the adventitia
adventitial invasive pattern: local invasion of the media with preservation of the intima
concentric bilayer pattern: inflammatory infiltration of adventitia and intima with preservation of the media
panarteritic pattern: inflammatory infiltrates in the three arterial layers
Location
Can potentially affect any medium to large-sized vessels, affecting the aorta (~20% of cases 7) and its major branches, particularly the extracranial branches of the external carotid artery 6.
Radiographic features
Ultrasound
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increased diameter of the superficial temporal artery (or other imaged vessels, e.g. vertebral artery 20) and hypoechoic wall thickening (halo sign)
with duplex ultrasound, 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
edematous wall swelling of superficial temporal artery 16
stenosis may be present but is not a specific sign for giant cell arteritis 8
CT
Findings on CT include:
wall thickening of affected segments
calcification
mural thrombi
Arterial phase CT (angiography) is useful for assessing luminal abnormalities:
stenoses
occlusions
dilatations
aneurysm formation
MRI
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T1 C+ (Gd)
best sequence for assessment
shows mural inflammation very well 2,4
mean wall thickness increased in the affected region
luminal diameter correspondingly decreased in the affected region
reported approximate sensitivity and specificity is 80% and 97%, respectively 2
Treatment and prognosis
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.
Complications
thoracic aortic aneurysms (more commonly ascending aorta) 7
aortic dissection (more commonly ascending aorta) 7
vision loss 17
focal neurological deficits from ischemic stroke
Differential diagnosis
Imaging differential considerations include:
Takayasu arteritis: affects younger patients (<50 years) and affects more proximal vessels