Table 1.

Susceptibility-weighted imaging collateral grades.

Collateral grade	Description of collateral status
Good	No prominent cortical or medullary vein in the affected hemisphere (prominent cortical vein score 0 or prominent medullary vein score 0)
Intermediate	Mildly prominent cortical and/or medullary veins in the affected hemisphere (prominent cortical vein score 1 and/or prominent medullary vein score 1)
Poor	1. Moderately prominent cortical and/or medullary veins in the affected hemisphere (prominent cortical vein score 2 and/or prominent medullary vein score 2)
	2. Very prominent cortical or medullary veins in the affected hemisphere (prominent cortical vein score 3 or prominent medullary vein score 3)
Very poor	Very prominent cortical and medullary veins in the affected hemisphere (prominent cortical vein score 3 and prominent medullary vein score 3)