Vascular anatomy
The demographic data of the subjects are summarized in Table 1. All 210 subjects were asymptomatic Han-Chinese adults, and only 81 (38.6%) had complete symmetric of the COW. Seven subjects with bilateral F-PCAs and symmetric A1s were not included in the symmetric group due to a lack of bilateral P1 segments. Sixty-seven subjects had asymmetric A1 segments (31.9% of all cases), including 19 (9%; AA1 group) with unilateral A1 aplasia, 33 (15.7%; AA2 group) with ≥50% A1 asymmetry, and 15 (7.1%; AA3 group) with < 50% A1 asymmetry.
Table 1 Subjects demographic data by Circle of Willis variants
All Symmetrica A1 Asymmetry (AA group)b PcomA Asymmetry (PA group)c
AA1 AA2 AA3 P-value PA1d PA2 PA3 P-value
Number of cases 210 81 (38.6%) 19 (9%) 33 (15.7%) 15 (7.1%) 15 (7.1%) 45 (21.4%) 18 (8.6%)
Age (years) 53.9 ± 9.4 50.4 ± 9.3 52.6 ± 11.5 54.6 ± 10.1 49.9 ± 8.3 0.344 55.4 ± 7.9 53.3 ± 9.5 51.8 ± 7.0 0.507
Right-side 6 (31.6%) 8 (24.2%) 7 (46.7%) 0.311 10 (66.7%) 29 (64.4%) 14 (77.8%) 0.588
Sex
 Female 77 (36.7%) 32 (39.5%) 7 (36.8%) 8 (24.2%) 4 (26.7%) 0.601 7 (46.7%) 15 (33.3%) 10 (55.6%) 0.262
 Male 133 (63.3%) 49 (60.5%) 12 (63.2%) 25 (75.8%) 11 (73.3%) 8 (53.3%) 30 (66.7%) 8 (44.4%)
Height (cm) 165.2 ± 8.1 165.2 ± 8.7 166.7 ± 8.2 165.5 ± 6.6 166.1 ± 6.1 0.841 163.3 ± 7.8 165.6 ± 8.7 163.4 ± 7.6 0.494
Weight (Kg) 68.0 ± 13.2 69.6 ± 14.6 69.4 ± 13.7 65.8 ± 9.9 69.7 ± 13.7 0.428 64.9 ± 11.4 67.9 ± 13.5 64.5 ± 11.0 0.543
Heart rate (/min) 67.3 ± 10.0 66.8 ± 11.1 65.8 ± 10.4 68.3 ± 8.0 65.5 ±12.6 0.551 67.8 ± 8.2 68.4 ± 7.9 69.7 ± 12/0 0.820
aSeven subjects with bilateral F-PCAs were excluded
bTwenty-three patients in the AA group had PcomA asymmetry, including 2 PA1, 14 PA2, and 7 PA3
cTwenty-three patients in the PA group had A1 asymmetry, including 5 AA1, 13 AA2, and 5 AA3
dThirty-seven subjects with 45 F-PCA, with 20 right-side F-PCA, 9 left-side F-PCA, and 8 bilateral F-PCAs
Seventy-eight subjects (37.1% of all cases) were included in the PA group, including 15 in the PA1 group (7.1%) with a unilateral F-PCA and absent contralateral PcomAA, 45 in the PA2 group (21.4%) with ≥50% PcomA asymmetry, and 18 in the PA3 group (8.6%) with < 50% PcomA asymmetry. Twenty-three subjects had both A1 and PcomA asymmetry. In these subjects, the dominant A1 was most likely to be on the same side as the non-dominant PcomA (19 patients, P < 0.001, McNemar’s test). Only 4 subjects had the dominant A1 and dominant PcomA on the same side.