Cerebral vasomotor reactivity in reversible cerebral vasoconstriction syndrome

Background Altered cerebrovascular tone is implicated in reversible cerebral vasoconstriction syndrome (RCVS). We evaluated vasomotor reactivity using bedside transcranial Doppler in RCVS patients. Methods In this retrospective case-control study, middle cerebral artery (MCA) blood flow velocities were compared at rest and in response to breath-hold in RCVS (n = 8), Migraineurs (n = 10), and non-headache Controls (n = 10). Hyperventilation response was measured in RCVS. Results In RCVS, Breath Holding Index (BHI) was severely reduced in seven of eight patients and 14/16 MCAs; seven of 16 MCAs showed exhausted (BHI < 0.1) or inverted (BHI < 0) vasomotor reactivity. Mean BHI in RCVS (0.23 ± 0.5) was significantly lower than Migraine (1.52 ± 0.57) and Controls (1.51 ± 0.32), p < 0.001. Triphasic velocity responses were seen in all groups. The maximum V_mean decline during the middle negative phase was -'15.5 ± 9.2% in RCVS, -'15.4 ± 7% in Migraine, and -'10.3 ± 5% in Controls (p = 0.04). In the late positive phase, average V_mean increase was 6.2 ± 14% in RCVS, which was significantly lower (p < 0.001) than Migraine (30.5 ± 11%) and Controls (30.2 ± 6%). With hyperventilation, RCVS patients showed 23% decrease in V_mean. Conclusion Cerebral arterial tone is abnormal in RCVS, with proximal vasoconstriction and abnormally reduced capacity for vasodilation. Further studies are needed to determine the utility of BHI to diagnose RCVS before angiographic reversibility is established, and to estimate prognosis.