A 58-year-old man presents with sudden onset of severe headache, jaw claudication, and visual disturbances. Temporal artery biopsy shows granulomatous inflammation with giant cells. What is the most common site of arterial involvement in this condition?

Explanation

## Giant Cell Arteritis: Most Common Sites of Involvement **Key Point:** Giant cell arteritis (GCA), also known as temporal arteritis, predominantly affects medium and large arteries, with the temporal and ophthalmic arteries being the most frequently involved vessels. ### Pathophysiology GCA is a granulomatous vasculitis of medium and large arteries that occurs in elderly patients (>50 years). The inflammatory process preferentially targets elastic arteries, particularly those in the head and neck region. ### Most Common Sites of Involvement | Site | Frequency | Clinical Significance | |------|-----------|----------------------| | **Temporal artery** | >90% | Diagnostic site; biopsy gold standard | | **Ophthalmic artery** | 50-80% | Risk of vision loss/blindness | | **Posterior ciliary arteries** | Common | Anterior ischemic optic neuropathy | | **Aorta and branches** | 10-15% | Late complication; aortic regurgitation | | **Coronary arteries** | <5% | Rare; can cause MI | | **Mesenteric arteries** | Rare | Unusual presentation | **High-Yield:** The **temporal artery** is the pathognomonic site and the diagnostic target for biopsy. The **ophthalmic artery** involvement explains the vision-threatening complications (amaurosis fugax, permanent blindness). ### Clinical Pearl Temporal artery tenderness, prominence, and pulselessness on examination correlate with biopsy-proven GCA. The ophthalmic artery is a branch of the internal carotid (via the cavernous sinus), and its involvement leads to anterior ischemic optic neuropathy (AION) — the most feared complication. ### Why Other Sites Are Less Common - **Coronary arteries:** Involved in <5% of cases; not the typical presentation - **Aortic arch:** Involved in 10–15% as a late manifestation; not the primary site - **Mesenteric arteries:** Rarely involved; not a characteristic feature **Mnemonic:** **TEMPORAL** — The classic presentation: **T**emporal artery involvement, **E**lderly (>50), **M**onocular vision loss, **P**olymyalgia rheumatica (50% association), **O**phthalmic artery at risk, **R**aised ESR/CRP, **A**cute headache, **L**arge vessel granulomatous vasculitis.