Size of affected vessels in primary angiitis of the CNS: associations with clinical features, medical management and functional outcomes

Background Primary angiitis of the central nervous system (PACNS) presents with heterogeneous clinical manifestations. Since implications of specific patterns of vessel size involvement are not well elucidated, this study aimed to investigate individual disease courses by involved vessel calibers and systematically assess clinical outcomes, relapses, and demographic data. Methods This single-center retrospective study (January 2010–April 2022) included 105 cerebral vasculitis patients. PACNS cases ( n = 49) were stratified into four groups based on radiological vessel involvement: large vessels (Group 1), large and medium-sized vessels (Group 2), small/peripheral vessels (Group 3), and mixed vessel involvement (Group 4). Data on demographics, risk factors, imaging findings, and clinical outcomes were analyzed. Results Among 49 PACNS patients (53.1% female, mean age 46.8 years), cardiovascular risk factors, specifically body weight ( p = 0.021), showed significant differences between groups. Biopsies were positive exclusively in cases with small vessel involvement across all groups ( n = 9). Cyclophosphamide usage was higher in patients with small vessel involvement ( p 0.05). Patients with exclusive small vessel involvement showed greater functional decline ( p = 0.002 for 2nd relapse), more severe imaging progression ( p = 0.012 for 3rd relapse) and a trend toward more relapses overall compared to groups without small vessel involvement. Conclusion Despite a limited sample size due to the rarity of the disease, our study highlights vessel size as a key factor in PACNS heterogeneity, associating small vessel involvement with worse functional outcomes, greater imaging progression, and distinct treatment patterns. These findings underscore the importance of vessel size in understanding PACNS pathophysiology and guiding management.