Giant Cell Arteritis: The Primary Autoimmune Disorder Causing Headache in Older Adults
Giant cell arteritis (GCA) is the autoimmune disorder that causes headache, particularly in adults over 50 years of age, and represents the most common primary systemic vasculitis in this population. 1, 2
Clinical Presentation
Cardinal Symptoms
Headache is the hallmark symptom of GCA, occurring in approximately 90% of patients with biopsy-confirmed disease. 2, 3 The headache is typically new-onset or represents a significant change in headache pattern in someone over 50 years old. 2, 4
Key diagnostic features include:
- Jaw claudication (pain with chewing) is the most specific symptom with a positive likelihood ratio of 4.90, present in approximately 50% of patients 2
- Temporal artery abnormalities including thickening (LR+ 4.70), loss of pulse (LR+ 3.25), or tenderness on palpation (LR+ 3.14) 1, 2
- Visual disturbances occur in 20% of patients before blindness, including transient vision loss, diplopia, or blurred vision 2
- Constitutional symptoms such as fever, malaise, and weight loss may dominate the presentation 3, 5
High-Risk Complications
Untreated GCA carries a 14-18% risk of vision loss, which can increase to 50% without treatment, making this a medical emergency. 2 Other serious ischemic complications include stroke, cranial nerve palsy, and scalp necrosis. 6
Diagnostic Approach
Laboratory Testing
Elevated inflammatory markers are present in more than 95% of GCA cases at diagnosis: 2
- ESR >100 mm/h has a positive likelihood ratio of 3.11 2
- Absence of ESR >40 mm/h has a negative likelihood ratio of 0.18 (essentially rules out GCA) 2
- CRP ≥2.5 mg/dL absence has a negative likelihood ratio of 0.38 2
- Platelet count >400 × 10³/μL has a positive likelihood ratio of 3.75 2
Confirmatory Testing
Temporal artery biopsy remains the gold standard for diagnosis, but treatment must not be delayed while awaiting biopsy results. 1, 7 The biopsy specimen should be at least 1 cm in length and performed by an experienced surgeon. 2
Alternative imaging modalities when biopsy is negative or unavailable include: 2, 7
- Color duplex ultrasonography (showing circumferential arterial wall thickening)
- MRI
- PET-FDG (showing increased tracer uptake in arterial walls)
Immediate Management
Emergency Treatment Protocol
High-dose glucocorticoid therapy must be initiated immediately upon clinical suspicion of GCA, without waiting for biopsy confirmation, to prevent irreversible vision loss. 1, 2
The treatment algorithm is:
Initiate prednisone 40-60 mg/day (or 0.7-1 mg/kg/day) immediately when GCA is suspected based on clinical presentation and elevated inflammatory markers 1, 3
Add low-dose aspirin (75-150 mg/day) for all GCA patients to protect against cardiovascular and cerebrovascular events 2
Consider tocilizumab as adjunctive therapy to reduce glucocorticoid requirements and flare rates, particularly in patients at high risk for steroid-related complications 1, 2, 5
Methotrexate may be considered as a steroid-sparing agent in patients with frequent relapses or significant corticosteroid-related morbidity 1, 5
Critical Pitfalls to Avoid
Do not withhold corticosteroids while awaiting temporal artery biopsy results—the risk of permanent blindness outweighs any diagnostic uncertainty. 1, 7 Corticosteroid treatment can be initiated up to several days before biopsy without significantly affecting diagnostic yield. 7
Do not dismiss the diagnosis in patients with atypical presentations, including those with normal or low ESR (rare but possible), fever of unknown origin, or chronic cough as the primary symptom. 1, 7 The disease can present with overlapping features of tension-type headache, leading to diagnostic delays. 8
Infliximab should not be used to treat GCA, as it is associated with higher rates of disease activity and recurrent ocular symptoms. 1
Monitoring and Long-Term Management
Patients require prolonged treatment with gradual corticosteroid taper based on clinical symptoms and inflammatory markers, as relapse is common, especially during the first year. 1, 3, 5 Clinical monitoring should include periodic assessment for both disease activity and corticosteroid-related complications. 2
Periodic imaging may be necessary to assess for large-vessel involvement and development of complications such as aortic aneurysms and vascular stenoses. 2, 6