Objective: Reversible cerebral vasoconstriction syndromes (RCVS) are characterized by thunderclap headaches and reversible cerebral vasoconstrictions. No systematic studies on cerebral hemodynamics have been published. Methods: Patients with RCVS were consecutively recruited. Sequential transcranial color-coded sonography studies were performed on the middle cerebral artery (MCA) for 3 months. Mean flow velocities (VMCA) and Lindegaard Index (LI) were recorded and compared with those of controls. Results: Thirty-two patients (all female; average age, 49-7 ± 6.8 years) were enrolled. Four developed reversible posterior leukoencephalopathy syndrome, and two of them, ischemic strokes. One hundred and twenty-six sonography studies were performed on 57 eligible MCAs. The mean maximum VMCA (109.5 ± 30.8cm/sec) and LI (2.2 ± 0.7) of RCVS patients exceeded those of controls (VMCA: 66.3 ± 9.5cm/sec, p <0.001; LI: 1.4 ± 0.3, p <0.001). The VMCA and LI levels were still at their plateau at the mean time (day 22 after headache onset) of headache resolution. Fifteen (46.9%) patients had VMCA exceeding 120cm/sec, and 5 (16%) had LI exceeding 3. Patients fulfilling the criteria of subarachnoid hemorrhage mild vasospasm (n = 4; 13%), that is, both VMCA greater than 120cm/sec and LI greater than 3, had a greater risk of posterior leukoencephalopathy (75 vs 4%; p = 0.003) and ischemic strokes (50 vs 0%; p = 0.01) than those without. Interpretation: Patients with RCVS experienced prolonged vasoconstriction, making the risk for posterior leukoencephalopathy and ischemic strokes outlast headache resolution. Patients fulfilling mild vasospasm criteria for subarachnoid hemorrhage carry a high risk.
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