Fig. 1

Flow diagram of the subject enrollments. *Suboptimal imaging: 4 with metallic artifacts due to dental prothesis; 3 with asymmetric scans; 1 with file storage error. **Onset to MRI interval: acute ≤ 30 days; remission ≥ 90 days; non-acute and non-remission are those > 30 and < 90 days. DTI = Diffusion tensor imaging; DTI-ALPS = Diffusion-tensor imaging along the perivascular space; HC = Healthy control; HIT-6 = The six-item Headache Impact Test; ICA = Internal carotid artery; MR = Magnetic resonance; RCVS = Reversible cerebral vasoconstriction syndrome; RI = Resistance index; TCCS = Transcranial color-coded duplex sonography; T1WI = T1-weighted imaging; T2-FLAIR = T2-fluid-attenuated inversion recovery