Table 3:

Proposed criteria for differentiating RCVS vasoconstriction from SAH vasospasm10

RCVS VasoconstrictionVasospasm-Aneurysmal SAH
No evidence of ruptured aneurysm or vascular malformationPlausible target lesion identified
Diffuse and disproportionate extent of cerebral vasoconstriction relative to amount of SAHSeverity 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 branchesSmooth, 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 weeksDevelopment of vasospasm peaking between 4 and 14 days after hemorrhage