MR angiography study on morphology of the Willis' circle in healthy Chinese male adults with variation of A1 segment of anterior cerebral artery

Objective: To investigate the variations of multi-segments of the Willis' circle in cases with ACA-A1 variation. Methods: Retrospective comparative analysis was applied to images of 2246 healthy cases which were excluded from abnormalities of physical and biochemistry examination and angiostenosis caused by angiosclerosis. We divided variant group and contrast group according to variation of ACA-A1 segment. Several aspects were carried to comparison: the variation between bilateral ACA-A1 segment within the variant group was studied by χ² test; the proportion of FTP and developing of PCA-P1 were put into test. Finally we use trend χ² test to compare the variation degree of ACA-A1, ipsilateral FTP formation and PCA-P1 variation. Results Variants of AC A-A1 contains 634 cases whereas normal cases were 1612. A prominence in variation revealed in right side of ACA-A1 (χ² = 26.19, P < 0.01) which revealed by 429 cases in right side versus 205 cases in left side respectively-paralleled with contrast group, the variant group showed immensely advantages in high proportion of FTP (χ² = 14.165, P < 0.01) which indicated by variant group 22.56% (143/634) and contrast group 18.30% (295/1612); but crippled in PCA-P1 formation (χ² = 4.32, P < 0.05) which illustrated by proportions of by dysplasia and deficiency compared by variant group and contrast group was 17.35%(110/634), 14.21%(229/1612). ACA-A1 normal, slight variation, dysplasia and deficiency together with FTP dyformation was 9.15%(58/634), 15.62%(52/333), 16.50%(34/206), 23.16%(22/95) respectively. Within the variation group, a pattern between ACA-A1 and FTP which fluctuated simultaneously with significant statistical discrepancies (χ² = 51.117, P < 0.01; linear by linear χ² = 13.340, P < 0.01) which demonstrated by ACA-A1 normal, slight variation, dysplasia, deficiency together with FTP formation was 457%(29/634), 12.91%(43/333), 16.02%(33/206), 20.00%(19/95) respectively, as far as ACA-A1 variation was concerned, The variant group were more prone to develop PCA-P1 dysplasia or deficiency (χ² = 45.87, P < 0.01; linear-by-linear χ² = 43.474, P < 0.01). Conclusions: There were more multi-variation of Willis' circle in the cases with ACA-A1 variation, MR A can value the anatomy and variation of the Willis' circle. MRA can also guide the clinic diagnosis, treatment and prognosis of the cerebrovascular diseases. (authors)