Temporal arteritis, also known as giant cell arteritis (GCA) is a medium and large vessel vasculitis. It involves the extracranialbranches of the common carotid, internal carotid, and external carotid arteries, with the temporal artery (a branch of the external carotid) being the most commonly affected vessel. It is common in individuals >50 years of age.
Pathophysiology
The cause of temporal arteritis is not known. Genetics and environmental factors both seem to be implicated:
- Genetic factors - HLA class II mutations.
- Environmental factors - certain infections may contribute but evidence is not conclusive.
What occurs in temporal arteritis is T-cells and macrophages infiltrate the adventitial (outer) layer of the arteries. These T-cells release interferon-γ (IFN-γ) which stimulates the macrophages. Chronic stimulation of macrophages results in formation of multinucleated giant cells (they are present in about 50% of cases). Inflammatory cytokines such as IL-1 and IL-6 cause systemic inflammation. Matrix metalloproteinases (MMPs) and reactive oxygen species (ROS) released into the tunica media layer of the artery results in tissue injury and separation of the media and intima layers.
The artery subsequently releases growth factors which stimulates the development of new vessels as well as thickening of the tunica intima layer of the injured artery. This then leads to narrowing of the vessel and ischaemia which can lead to the symptoms felt.
⚠️ Risk factors
- Aged ≥50 years old
- Female sex
- Northern European ancestry
😷 Presentation
Temporal arteritis may have an acute or insidious onset. Features present on the face, eyes and systemically:
- Facial features:
- Temporal headache - we have to consider GCA in any elderly person with temporal headache, as >85% of patients have GCA
- Thickened & tender, palpable temporal arteries - which may be pulseless.
- Jaw claudication - due to affectation of the internal maxillary artery and facial artery.
- Ophthalmic features:
- Diplopia - results from the involvement of any part of the oculomotor system such as the cranial nerves
- Vision loss - due to:
- Amaurosis fugax (transient monocular visual loss)
- Central retinal artery occlusion - as the central retinal artery is the first branch of the ophthalmic artery.
- Irreversible painless blindness (permanent monocular vision loss) - due to untreated anterior ischaemic optic neuropathy (AION). AION accounts for the majority of ocular complications of GCA. It results from occluding the posterior ciliary artery (a branch of the ophthalmic artery) → ischaemia of the head of the optic nerve.
- Fundoscopy typically shows a swollen pale disc and blurred margins.
- Systemic features:
- GCA and polymyalgia rheumatica (PMR) are strongly linked, and so symmetrical proximal muscle stiffness (usually shoulders neck and pelvic girdle) and an oligoarthritis may occur. 50% of patients who have GCA will also have PMR features.
- Lethargy
- Depression
- Low-grade fever
- Anorexia
- Night sweats
🔍 Investigations
- 🥇 Bloods
- ESR - elevated. ESR is highly specific for GCA and is highly unlikely if ESR is not elevated.
- LFTs - abnormal in 1/3rd of patients (especially ALP).
- FBC - normocytic normochromic anaemia and thrombocytosis are often present.
- 🥇 Fundoscopy - key in all patients. AION shows a swollen pale disc and blurred margins.
- 🥇 Vascular ultrasonography - a non-compressible halo sign (wall thickening) is the finding that most indicates GCA.
- 🏆 Temporal artery biopsy - confirms the diagnosis, but, due to skip lesions, a negative biopsy does not rule out GCA.
🧰 Management
A combination of specialties manages patients with GCA:
- Rheumatology for specialist diagnosis and management
- Vascular surgeons for a temporal artery biopsy
- Ophthalmology review for visual symptoms
- Neurology in the case of stroke of neurological deficits
GCA is a medical emergency due to the risk of permanent blindness. Therefore, treatment with steroids must be started as soon as GCA is suspected.
The type of steroids given are dependent on the presence of vision loss or jaw claudication:
- Urgent ophthalmology review - is necessary but should not delay steroid treatment.
- No vision loss or jaw claudication:
- 🥇 Oral prednisolone - 40-60 mg OD, dose is normally reduced very slowly over several months. Treatment is often required for 1–2 years, but people may require low doses for several years.
- 🥈 Azathioprine - may be given in place of steroids if weaning off of steroids are problematic.
- Acute or intermittent visual loss or jaw claudication:
- 🥇 IV methylprednisolone - 500-1000 mg.
- 🥈 Oral prednisolone (60-100 mg) may be given for up to 3 consecutive days if IV steroids are not possible.
- This is followed by oral prednisolone. Treatment is often required for 1–2 years, but people may require low doses for several years.
Other medications that may be prescribed:
- Bisphosphonates, calcium vitamin D to protect against osteoporosis due to steroid use.
- PPIs to protect against gastric ulcers due to steroid use.
- Aspirin to reduce risk of stroke and amaurosis fugax.
🚨 Complications
- Irreversible painless blindness - due to AION.
- Stroke - due to bilateral damage to the vertebral arteries, branches of the subclavian arteries.
Stroke is uncommon in GCA. The occurrence of stroke within the first 4 weeks of the diagnosis of GCA is reported in 3% of patients. Though strokes due to GCA can occur in the distribution of both the internal carotid and vertebrobasilar arteries (from the subclavian arteries), they are more common in the latter location.
Involvement of the vertebral arteries can result in vertigo, ataxia, dysarthria homonymous hemianopsia, or bilateral cortical blindness. Bilateral vertebral artery involvement can cause rapidly progressive brainstem and/or cerebellar neurologic deficits with high mortality.
The actual prevalence of GCA in ischemic stroke as a whole is low.