giant cell arteritis

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.

Epidemiology

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

Clinical presentation

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

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 .

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

In a study of 285 patients with biopsy-proven giant cell arteritis there were 4 main histological patterns :

  • 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 ) and its major branches, particularly the extracranial branches of the carotid artery .

    Markers
    Associations
    Complications

    Radiographic features

    Ultrasound
    • increased diameter of the superficial temporal artery and hypoechoic wall thickening (halo sign)
      • with duplex ultrasound, sensitivity is 87% and specificity is 96% 
      • more specific for giant cell arteritis if bilateral
      • 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
    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
    • T1 C+ (Gd)
      • the best sequence for assessment
      • shows mural inflammation very well
      • 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  

    Treatment and prognosis

    Treatment is with corticosteroid therapy and aspirin . Methotrexate may be used in combination with corticosteroid therapy initially, or as a corticosteroid-sparing drug .

    Differential diagnosis

    Imaging differential considerations include: