Temporal Arteritis (Giant Cell Arteritis)

Overview

Giant cell arteritis (GCA), also known as temporal arteritis or cranial arteritis, is the most common systemic vasculitis in adults. It is a granulomatous panarteritis that selectively targets medium and large-sized arteries, displaying a strong tropism for the branches of the external carotid artery (particularly the superficial temporal artery) and the aorta.

The disease occurs almost exclusively in individuals older than 50 years of age and is closely associated with Polymyalgia Rheumatica (PMR). GCA is considered a medical emergency: transmural inflammation and luminal stenosis of ophthalmic arteries can lead to irreversible anterior ischemic optic neuropathy (AION) and sudden, permanent blindness. Prompt recognition and immediate empiric corticosteroid therapy are critical to prevent catastrophic visual loss.

Giant cell arteritis does not always involve the temporal artery and can affect other medium and large arteries including the aorta.

Classification

Under the Chapel Hill Consensus Conference criteria, GCA is classified as a Large Vessel Vasculitis (LVV) alongside Takayasu Arteritis.

Feature	Giant Cell Arteritis (GCA)	Takayasu Arteritis
Age of Onset	> 50 years (peak 70–80 years)	< 50 years (peak 20–30 years)
Geographic / Ethnicity	Northern European descent	Asian descent
Primary Vessels	Cranial branches of external carotid, aorta	Aorta and its major primary branches
PMR Association	Strongly associated (~50% of cases)	Not associated

Pathophysiology

1. Immune Activation in Adventitia: Resident dendritic cells in the arterial adventitia become activated, releasing chemokines that recruit circulating CD4+ T-lymphocytes (differentiating into Th1 and Th17 subsets).
2. Granulomatous Panarteritis: Activated T-cells secrete Interferon-gamma (IFN-gamma), which transforms macrophages into multinucleated giant cells within the media and intima, forming characteristic granulomas.
3. Arterial Wall Destruction: Macrophages release Matrix Metalloproteinases (MMPs) and Reactive Oxygen Species (ROS), causing fragmentation of the internal elastic lamina.
4. Intimal Hyperplasia & Luminal Occlusion: Vascular Endothelial Growth Factor (VEGF) and Platelet-Derived Growth Factor (PDGF) drive smooth muscle proliferation and intimal thickening, culminating in arterial lumen stenosis, thrombosis, and distal tissue ischemia.

Clinical Manifestation

Diagnosis

• Elevated ESR/CRP
• Temporal artery biopsy (Gold Standard)
  • Histopathology: Shows transmural inflammation, multinucleated giant cells, histiocytes, T-cell infiltration, intimal hyperplasia, and fragmentation of the internal elastic lamina.
  • Biopsy Length: Specimen length must be at least 1.5–2.0 cm to account for “skip lesions”.
  • Biopsy should be performed within 1–2 weeks of starting steroids; do NOT delay steroid administration while awaiting biopsy.
• Imaging Studies (support diagnosis and can be used second line for diagnosis)
  • Temporal Artery Ultrasound: Non-invasive first-line alternative showing the “Halo Sign” (hypoechoic circumferential wall edema around the arterial lumen).
  • PET-CT / CT Angiography / MR Angiography: Used to evaluate extracranial large-vessel involvement (aortitis, subclavian, or axillary artery involvement).

Treatment

Management centers on rapid suppression of arterial inflammation using systemic corticosteroids and steroid-sparing biologic agents.

Corticosteroid Therapy (Immediate Initiation)

• Uncomplicated GCA (No visual loss or amaurosis fugax):
  • Start Oral Prednisone 40–60 mg daily immediately upon clinical suspicion.
• Complicated GCA (Active visual loss or amaurosis fugax):
  • Start IV Pulse Methylprednisolone 500–1000 mg daily for 3 consecutive days before transitioning to high-dose oral Prednisone.
• Tapering Schedule: Maintain high dose for 2–4 weeks until symptoms resolve and inflammatory markers normalize, then slowly taper over 12–24 months.

Steroid-Sparing Biologic Agents

• Tocilizumab (Anti-IL-6 Receptor Monoclonal Antibody)

Adjuvant & Preventative Care

• Low-dose Aspirin (75–100 mg daily) to reduce cranial ischemic events.
• Bisphosphonates, Calcium, and Vitamin D co-prescription for all patients on long-term steroid therapy.
• PPI

Complications & Prognosis

Complications

• Permanent Blindness: Bilateral in up to 20–50% of untreated cases due to irreversible AION or central retinal artery occlusion (CRAO).
• Thoracic aortic aneurysms occur 17 times more frequently in GCA patients than age-matched controls, often presenting late (years after initial diagnosis).
• Ischemic stroke secondary to vertebrobasilar or carotid artery occlusion.
• Iatrogenic Corticosteroid Toxicity
  • Osteoporosis/fractures
  • Diabetes mellitus
  • Hypertension, cataracts
  • Secondary infections
  • Myopathy.

Prognosis

• Vision lost prior to initiating steroid therapy rarely recovers, but immediate treatment protects the contralateral eye in > 95% of cases.
• Relapses occur in 30–50% of patients during steroid tapering, requiring prolonged treatment (average duration 2 years).
• Periodic imaging (e.g., chest X-ray, CT, or MRI every 2–5 years) is recommended to screen for late thoracic aortic aneurysms.

References

1. Weyand CM, Goronzy JJ. Clinical practice. Giant-cell arteritis and polymyalgia rheumatica. N Engl J Med. 2014;371(1):50-57. doi:10.1056/NEJMcp1214825
2. Dejaco C, Brouwer E, Mason JC, et al. To scan or not to scan in giant cell arteritis: imaging first strategy. Ann Rheum Dis. 2023;82(2):167-174. doi:10.1136/ard-2022-223326
3. Stone JH, Tuckwell K, Dimonaco S, et al. Trial of Tocilizumab in Giant-Cell Arteritis. N Engl J Med. 2017;377(4):317-328. doi:10.1056/NEJMoa1613849