TABLE 3:
Relationship between degree of collateral flow and observable laterality of PCA at MRA
Degree of Collateral Flow (Ipsilateral-Contralateral)
Score of PCA Laterality
2
1
0
P4–P2p
P4–P3
P3–P2p
P2p–P2a
P4–P4
P3–P3
P2a–P2a
Prominent
1
8
1
0
1
0
0
Mild
0
0
1
1
1
7
0
Absent
0
0
0
0
0
3
1