Temporal Arteritis (Giant Cell Arteritis)

Giant cell arteritis (GCA), or temporal arteritis, is a granulomatous large- and medium-vessel vasculitis affecting the extracranial branches of the carotid artery, the aorta and its major branches, occurring almost exclusively in people over 50 years.

It is the commonest primary systemic vasculitis of older adults; peak incidence is between 70 and 80 years, with women affected two to three times more often than men. Incidence is highest in Northern European populations and lower in India and Asia, although under-diagnosis contributes.

Men are more likely to have ocular manifestations. GCA and PMR are closely linked; Pathy's also notes that GCA must be considered as a cause of cerebrovascular disease and vertigo in older people.

It is a medical emergency — untreated it causes irreversible blindness, aortic aneurysm and stroke.

Dendritic cells in the adventitia are activated, recruiting CD4+ T cells that differentiate into Th1 (interferon-γ) and Th17 (IL-17) lineages; macrophages fuse to form multinucleate giant cells.

Histology: transmural granulomatous panarteritis with mononuclear infiltrate, giant cells adjacent to a fragmented internal elastic lamina, and intimal hyperplasia causing luminal occlusion — the intimal proliferation, not the inflammation itself, causes the ischaemic events.

Involvement is segmental and patchy ("skip lesions"), which is why a short or unilateral biopsy may be falsely negative.

IL-6 drives the systemic inflammatory response and the acute-phase reactants — the rationale for tocilizumab and sarilumab.

Cranial: new-onset temporal or occipital headache, scalp tenderness (pain on combing hair or lying on a pillow), and a thickened, tender, nodular, pulseless temporal artery.

Jaw claudication — pain in the masseters on chewing — is the most specific symptom; tongue claudication and, rarely, tongue or scalp necrosis occur.

Visual: amaurosis fugax, diplopia, and sudden painless monocular visual loss from arteritic anterior ischaemic optic neuropathy (chalky-white swollen disc), central retinal artery occlusion, or posterior ischaemic optic neuropathy. Untreated, the second eye is involved within days to weeks.

Systemic: fever, weight loss, anorexia, malaise, depression — GCA is an important cause of pyrexia of unknown origin in older people and may present as isolated unexplained inflammation.

Polymyalgic: shoulder and hip girdle pain and stiffness in 40–50%.

Large-vessel disease: limb claudication, asymmetrical blood pressures, absent or unequal pulses, subclavian or carotid bruits; late thoracic aortic aneurysm and dissection.

Neurological: transient ischaemic attack and stroke, predominantly in the vertebrobasilar territory; GCA-related stroke is defined as an ischaemic infarct within three to four weeks of diagnosis and treatment.

ESR and CRP are markedly elevated; ESR is often above 75–100 mm/hour. CRP is the more sensitive; up to 4% of biopsy-proven cases have normal inflammatory markers.

Supporting bloods: normocytic anaemia, thrombocytosis, raised alkaline phosphatase, hypoalbuminaemia, raised IL-6.

Temporal artery biopsy is the diagnostic gold standard. Practical rules: take a segment of at least 1–2 cm with serial sectioning to overcome skip lesions; consider bilateral biopsy; do not delay steroids for the biopsy — histology remains positive for up to 2–4 weeks after starting treatment. Kane's emphasises that any symptom suggestive of temporal artery involvement — headache, jaw claudication, recent visual change — especially with an ESR above 75 mm/hour, should prompt consideration of temporal artery biopsy.

Colour Doppler ultrasound of temporal and axillary arteries showing the non-compressible "halo sign" is now a first-line, non-invasive test.

Cross-sectional imaging for large-vessel disease: FDG-PET/CT, CT angiography or MR angiography of the aorta and branches; MRI of the cranial vessels with contrast can show mural enhancement.

1990 ACR classification criteria (3 of 5): age at onset ≥50 years, new headache, temporal artery abnormality, ESR ≥50 mm/hour, and abnormal artery biopsy. The 2022 ACR/EULAR criteria add imaging findings and a positive biopsy weighting.

Acute treatment of temporal arteritis with high-dose steroids is needed to prevent blindness (Kane's) — start immediately on clinical suspicion, before biopsy.

Dosing: uncomplicated GCA — prednisolone 40–60 mg/day. Visual loss or amaurosis fugax — IV methylprednisolone 500–1000 mg/day for 3 days then high-dose oral prednisolone. Visual loss already established in one eye is rarely reversed; treatment protects the fellow eye.

Taper slowly over 12–24 months, guided by symptoms and CRP; most patients need 1–2 years or longer, and relapse is common.

Low-dose aspirin 75–150 mg may be added to reduce ischaemic events, weighed against gastrointestinal bleeding risk with steroids.

Steroid-sparing therapy: tocilizumab (IL-6 receptor blocker, GiACTA trial) is licensed for GCA; methotrexate is an alternative with modest evidence.

Mandatory adjuncts in older adults: calcium, vitamin D and a bisphosphonate from day one; gastroprotection; monitoring for steroid-induced diabetes, hypertension, cataract, glaucoma, insomnia, mood disturbance, infection and steroid myopathy; and falls prevention.

Long-term surveillance: annual assessment for thoracic aortic aneurysm by imaging, since aortic complications occur years after the acute illness.

With prompt treatment, visual loss is largely preventable and life expectancy approaches that of the general population; the dominant long-term burden is glucocorticoid toxicity, followed by aortic aneurysm and relapse.