A 48-year-old man who presented with severe sudden headache. A, Axial nonenhanced CT at presentation demonstrates peripheral sulcal blood (arrow) with no hemorrhage at the basal cisterns and no history of trauma. B and C, Coronal (B) and sagittal (C) MIPs of the CTA reveal no aneurysm. D−F, Anteroposterior and lateral projections of a catheter angiogram of the right ICA (D and E) and a lateral projection of the left ICA angiogram (F) demonstrate multiple irregularities and narrowings in medium-sized vessels, including the M1 segment of the right MCA (arrows in D), A3 branches of the ACAs (arrows in E and F), P3 branches of the left PCA (black arrowheads in F), and M3 branches of the right and left MCA (white arrowheads in E and F). These findings on DSA suggest underlying vasculitis as the cause of hemorrhage. Retrospective analysis of coronal and sagittal MIP reconstructions of the CTA reveals reciprocal irregularities and narrowings at the M1 segment of the right MCA and at the A3 branches of the ACAs (arrows in B and C).