Background/Purpose: Isolated inflammation of small vessels including capillaries, venules and arterioles surrounding a normal temporal artery (SVI) in patients suspected of having giant cell arteritis (GCA) has been described in the literature. However, the significance of this finding remains controversial. Authors have described SVI as highly suggestive of vasculitis while others consider it to be a non-specific finding associated with aging, infection and malignant disease. We performed a systematic review of the literature in order to characterize the diagnoses, clinical, and laboratory manifestations of patients with periarterial temporal small vessel inflammation as a sole finding on TAB

Methods: A search of the English language literature from 1990-2019 was performed using the following search terms: temporal artery, giant cell arteritis, vasculitis, small vessel, inflammation, vasa vasorum, and periarteritis. Data was extracted for cases that displayed isolated inflammation of small blood vessels external to a spared temporal artery on TAB. Clinical diagnosis, clinical and laboratory manifestations and treatment were recorded and included age, sex, presence of headache, polymyalgia rheumatica (PMR), temporal artery (TA) abnormality, fever, visual symptoms, and corticosteroid therapy. Data was extracted from individual studies and pooled odds ratios were calculated.

Results: Eleven studies were identified that provided data on 324 TAB demonstrating inflammation of small blood vessels external to the temporal artery.  One hundred and fifteen (35.5%) were classified as definite or probable GCA and 80 of these (69.6%) had PMR symptoms. Fifty (15.4%) had isolated PMR. Twenty (6.2%), especially those having neutrophilic infiltrates had other forms of vasculitis. The remainder (42.9%) had other illnesses including infection, malignancy or undiagnosed conditions. Five studies reported clinical data on patients with SVI classified as GCA. The mean age was 73.2 years, 65.8% were male, 43.8% had headache, 9.8% had jaw claudication 23.7% had abnormal TA, 22.3% had fever and 30.5% had visual symptoms. Corticosteroid (CS) was administered to 79.4% (range- 39-100); 79% (range 59.6-100) responded.  When SVI was compared to classical GCA, three studies reported significantly fewer SVI patients with jaw claudication whereas 2 studies reported a significant increase in PMR in SVI. Meta-analysis of 4 studies reporting jaw claudication and PMR revealed a significant increase of PMR in SVI (pooled OR 5.92; CI 3.32-10.55; P< 0.001) and less jaw claudication in SVI (pooled OR 0.248; CI 0.13-0.50; P< 0.0001).

Conclusion: Inflammation of capillaries, venules and arterioles surrounding a normal temporal artery on TAB in patients suspected of having giant cell arteritis (GCA) should not be ignored. While the clinical phenotype differs from classical GCA, the high prevalence of PMR, and response to CS suggests that this finding is associated with the PMR-GCA spectrum in a significant proportion of patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/what-is-the-significance-of-periarterial-temporal-small-vessel-inflammation-svi-on-temporal-artery-biopsy-tab-in-the-diagnosis-of-vasculitis-a-systematic-review-and-meta-analysis/