Table 1. Classification of the Grade of Embolization Performance (E Grade).

E Grade A1:	≥50% of successful nidus embolization for compact (plexiform) type AVM
E Grade A2:	≥50% of successful nidus embolization and proximal occlusion of fistulous feeders for mixed (plexiform + fistulous) type AVM
E Grade B1:	<50% of successful nidus embolization for compact (plexiform) type AVM
E Grade B2:	<50% of successful nidus embolization and proximal occlusion of fistulous feeders for mixed (plexiform + fistulous) type
	AVM or remaining daughter nidus on diffuse type*
E Grade C:	No successful embolization (all proximal occlusion) for all feeders in any types of AVM or failed obvious size reduction (only change of vascular density)

^*: Including remnant daughter nidus on diffuse type