Giant cell arteritis

Giant cell arteritis (GCA) is a common granulomatous vasculitis affecting medium- to large-sized arteries. It may also be known as temporal arteritis or cranial arteritis, given its propensity to involve the extra-cranial carotid artery branches such as the temporal artery. 

Epidemiology

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

Clinical presentation

There are many possible clinical features that present in a subacute fashion ¹⁰:

• headache (most common) with or without scalp tenderness
• systemic symptoms (e.g. fever, fatigue, weight loss)
• jaw claudication
• transient vision loss (amaurosis fugax)
• permanent vision loss (e.g. due to anterior ischaemic optic neuropathy, central retinal artery occlusion, ischaemic stroke, etc.)
  • in such cases, there may be accompanying Charles-Bonnet syndrome
• weak pulse over the affected arteries
• bruits on auscultation over the affected arteries
• clinical features of an aortic aneurysm or dissection if the aorta is involved

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.

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 carotid artery ⁶.

Markers

• serum erythrocyte sedimentation rate (ESR): markedly raised
• serum C-reactive protein (CRP): often markedly raised

Associations

• polymyalgia rheumatica: seen in ~50% of cases

Complications

• thoracic aortic aneurysms (more commonly ascending aorta) ⁷
• aortic dissection (more commonly ascending aorta) ⁷

Radiographic features

Ultrasound

• increased diameter of the temporal artery 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 normalisation of the sonographic features
• stenosis may be present but is not a specific sign for giant cell arteritis ⁸

CT angiography

• may be useful for assessing luminal abnormalities, such as stenoses, occlusions, dilatations, and aneurysm formation
• may also show wall thickening of affected segments, calcification and mural thrombi

MRI

• T1 C+ (Gd)
  • the best sequence for assessment, and is reported to show 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 with corticosteroid therapy and aspirin ¹¹.

Differential diagnosis

Imaging differential considerations include:

• Takayasu arteritis: affects younger patients (<50 years) and affects more proximal vessels
• atherosclerotic disease