Stroke pattern in giant-cell arteritis mostly involves watershed areas☆

Context: Stroke related to giant cell arteritis (GCA) is rare and is associated with a poor outcome. One of the putative ischemic mechanisms is narrowing of the arterial lumen due to wall infiltration by inflammation and intimal proliferation, leading to reduced distal blood flow. It was hypothesized that GCA-related stroke could predominate in watershed areas (WA). Methods: Literature review including all cases of GCA-related stroke with brain images. Results: Among 75 cases of GCA-related stroke, the anterior and posterior territories were involved in 48 % and 62.6 %, respectively. Up to 88.9 % of cases of anterior stroke probably involved WA. WA lesions in the posterior territories were as follows: uni/bilateral middle cerebellar peduncle (MCP) lesions in 25.5 %, and with less confidence, non-wedge-shaped cerebellar lesions in 46.8 %, or combined lesions in 61.7 %. Stenosis or occlusion of the afferent artery was almost always observed. A few lesions were not easily explained by low flow. Discussion: Despite the limitations of arterial territory allocation especially in the posterior circulation, ischemic lesions mainly occurred in WA. MCP lesions, which were typically WA, were highly characteristic of GCA. Low flow downstream focal stenosis was the main, but not the unique, ischemic mechanism of GCA stroke.