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Giant Cell Arteritis

Summary

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  • Chronic granulomatous vasculitis affecting large and medium-sized arteries, particularly the extracranial branches of the carotid artery
  • Typically presents in older adults with headache, scalp tenderness, jaw claudication, and visual disturbances
  • Diagnosis confirmed by temporal artery biopsy; imaging plays a crucial role in assessment and monitoring

Pathophysiology

  • Characterised by granulomatous inflammation of the vessel wall, leading to:
    • Intimal hyperplasia
    • Luminal stenosis or occlusion
    • Fragmentation of the internal elastic lamina
  • T-cell-mediated immune response against arterial wall antigens
  • Associated with polymyalgia rheumatica in up to 50% of cases

Demographics

  • Predominantly affects individuals over 50 years of age
  • Incidence increases with age, peaking in the 7th and 8th decades
  • More common in women (female to male ratio 2-3:1)
  • Higher prevalence in Northern European populations

Diagnosis

  • Clinical presentation:
    • New-onset headache (70-80% of cases)
    • Scalp tenderness
    • Jaw claudication
    • Visual disturbances (up to 20% of cases)
    • Constitutional symptoms (fever, weight loss, fatigue)
  • Laboratory findings:
    • Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
    • Normocytic anaemia
    • Thrombocytosis
  • Temporal artery biopsy:
    • Gold standard for diagnosis
    • Sensitivity of 70-90%

Imaging

  • Ultrasound:
    • 'Halo sign': hypoechoic thickening of the vessel wall
    • Non-compressible temporal arteries
    • Sensitivity 68%, specificity 81%
  • CT angiography:
    • Mural thickening and enhancement
    • Luminal stenosis or occlusion
    • Useful for assessing large vessel involvement
  • MRI/MRA:
    • Mural oedema and enhancement
    • High sensitivity for detecting early vessel wall inflammation
    • Can assess both cranial and extracranial arteries
  • PET/CT:
    • Increased FDG uptake in affected vessels
    • Particularly useful for detecting large vessel involvement
    • Can aid in monitoring treatment response

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  • 75-year-old patient presented with visual impairment and right-sided jaw claudication.
  • CTA showed a vertebral artery occlusion (not shown) and bilateral occipital infarcts with haemorrhagic transformation on the admission scan.
  • CTA showed soft tissue thickening around both subcalvian arteries (red arrows) and the internal thoraic arteries (blue arrows) that corresponded to marked tracer uptake on FDG-PET.
  • VWI imaging showed mural enhancement along the length of the right temporal artery without a significant stenosis on the MRA (green arrows). This correlated to the halo sign on US (not shown).

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  • A 70-year-old patient presented with left sided visual impairment, orbital pain and a headache.
  • CT showed a haematoma in the left frontal lobe.
  • MRI showed diffusion restriction in the left optic nerve and hyperenhancement and swelling of the left extra-occular muscles.
  • VWI showed concentric enhancement within a stenosed segment of the left ICA (which was causing abnormal left MCA territory perfusion).
  • The vessel wall enhancement corresponded to increased tracer uptake on FDG-PET.
  • Following a biopsy of the inferior rectus muscle, a putative diagnosis of giant cell arteritis was made.

Treatment

  • Immediate initiation of high-dose corticosteroids upon suspicion of GCA
  • Initial dose: prednisolone 40-60 mg daily or equivalent
  • Gradual tapering of steroids over 12-24 months
  • Adjunctive therapy:
    • Methotrexate or other immunosuppressants for steroid-sparing effect
    • Tocilizumab (IL-6 receptor antagonist) approved for GCA treatment
  • Aspirin for prevention of ischaemic complications
  • Regular monitoring of disease activity and treatment response:
    • Clinical assessment
    • ESR and CRP
    • Imaging (ultrasound, MRI, or PET/CT) to evaluate vascular inflammation

Differential diagnosis

Differential diagnosis Differentiating feature
Takayasu's arteritis Younger patients (<40 years); predominantly affects the aortic arch and its branches; similar vessel wall thickening and enhancement on MRI/CTA; large vessel PET uptake
Primary angiitis of the CNS (PACNS) Small and medium intracranial vessel involvement; multifocal brain infarcts on MRI; leptomeningeal enhancement; no temporal artery involvement
Atherosclerosis Eccentric calcified plaques on CTA; no mural oedema or halo sign on ultrasound; no PET uptake in vessel wall