Proposed criteria for differentiating RCVS vasoconstriction from SAH vasospasm10
| RCVS Vasoconstriction | Vasospasm-Aneurysmal SAH |
|---|---|
| No evidence of ruptured aneurysm or vascular malformation | Plausible target lesion identified |
| Diffuse and disproportionate extent of cerebral vasoconstriction relative to amount of SAH | Severity of vasospasm correlates with amount of hemorrhage and is most pronounced in the vicinity of the lesion |
| Beaded appearance of alternating areas of segmental vasoconstriction preferentially involving distal 2nd- and 3rd-order cerebral branches | Smooth, long segmental narrowing for proximal arteries at circle of Willis |
| Development of vasoconstriction in first 4–5 days after symptom onset, or persistence past 3 weeks | Development of vasospasm peaking between 4 and 14 days after hemorrhage |