Table 2.

Houkin’s MRA score and grading [50].

Houkin’s Score			Houkin’s Grading
Main Artery	Findings	Score	Score	Grade
ICA	Normal	0	0–1	1
	C1 stenosis	1
	Discontinuity of C1 signal	2
	Invisible	3
MCA	Normal	0	2–4	2
	M1 stenosis	1
	Discontinuity of M1 signal	2
	Invisible	3
ACA	Normal A2 and its distal signal	0	5–7	3
	A2 and its distal signal decrease or loss	1
	Invisible	2
PCA	Normal P2 and its distal signal	0	8–10	4
	P2 and its distal signal decrease or loss	1
	Invisible	2