Characterization of Extracranial Giant Cell Arteritis with Intracranial Involvement and its Rapidly Progressive Subtype

Objective The objective of this study was to characterize patients with extracranial giant cell arteritis with intracranial involvement. Methods In a multicenter retrospective study, we included 31 patients with systemic giant cell arteritis (GCA) with intracranial involvement. Clinical characteristics, pattern of arterial involvement, and cytokine profiles were assessed. Patients with GCA without intracranial involvement (n = 17), and with intracranial atherosclerosis (n = 25) served as controls. Results Erythrocyte sedimentation rate (ESR) was elevated in 18 patients (69.2%) with and in 16 patients (100%) without intracranial involvement (p = 0.02). Headache was complained by 15 patients (50.0%) with and 13 patients (76.5%) without intracranial involvement (p = 0.03). Posterior circulation arteries were affected in 26 patients (83.9%), anterior circulation arteries in 17 patients (54.8%), and both territories in 12 patients (38.7%). Patients with GCA had vertebral artery stenosis proximal and, in contrast, patients with atherosclerosis distal to the origin of posterior inferior cerebellar artery (PICA). Among patients with GCA with intracranial involvement, 11 patients (37.9%) had a rapid progressive disease course characterized by short‐term recurrent ischemic events. The median modified Rankin Scale (mRS) at follow‐up in these patients was 4 (interquartile range [IQR] = 2.0–6.0) and 4 patients (36.4%) died. Vessel wall expression of IL‐6 and IL‐17 was significantly increased in patients with rapid progressive course. Interpretation Typical characteristics of GCA, headache, and an elevated ESR, are frequently absent in patients with intracranial involvement. However, differentiation of intracranial GCA from atherosclerosis can be facilitated by the typical pattern of vertebral artery stenosis. About one‐third of patients with intracranial GCA had a rapid progressive course with poor outcome. IL‐17 and IL‐6 may represent potential future treatment targets. ANN NEUROL 2021;90:118–129