Cortical Microhemorrhage Presentation of Small Vessel Primary Angiitis of the Central Nervous System

Objective Primary angiitis of the central nervous system (PACNS) is a rare vasculitis restricted to the brain, spinal cord, and leptomeninges. This study aimed to describe the imaging characteristics of patients with small vessel PACNS (SV‐PACNS) using 7 T magnetic resonance imaging (MRI). Methods This ongoing prospective observational cohort study included patients who met the Calabrese and Mallek criteria and underwent 7 T MRI scan. The MRI protocol includes T1‐weighted magnetization‐prepared rapid gradient echo imaging, T2 star weighted imaging, and susceptibility‐weighted imaging. Two experienced readers independently reviewed the neuroimages. Clinical data were extracted from the electronic patient records. The findings were then applied to a cohort of patients with large vessel central nervous system (CNS) vasculitis. Results We included 21 patients with SV‐PACNS from December 2021 to November 2023. Of these, 12 (57.14%) had cerebral cortical microhemorrhages with atrophy. The pattern with microhemorrhages was described in detail based on the gradient echo sequence, leading to the identification of what we have termed the “coral‐like sign.” The onset age of patients with coral‐like sign (33.83 ± 9.93 years) appeared younger than that of patients without coral‐like sign (42.11 ± 14.18 years) ( P = 0.131). Furthermore, the cerebral lesions in patients with cortical microhemorrhagic SV‐PACNS showed greater propensity toward bilateral lesions ( P = 0.03). The coral‐like sign was not observed in patients with large vessel CNS vasculitis. Interpretation The key characteristics of the coral‐like sign represent cerebral cortical diffuse microhemorrhages with atrophy, which may be an important MRI pattern of SV‐PACNS. ANN NEUROL 2024