The Angles Between A1and A2Segments Of The Anterior Cerebral Artery And Association With The Formation And Rupture Of The Anterior Communicating Artery Aneurysms

Objective:To evaluate the angles between Al and A2segments of the anterior cerebral artery and the relationship with the formation and rupture of the anterior communicating artery aneurysms (ACoAA).Methods:64cases of anterior communicating artery aneurysm and188cases of non-anterior communicating artery aneurysm which were randomly chosen in the same period were analyzed in our study. And A1-A2segment angles(lateral angles)were measured on MSCTA, the angular dimensions and differences were recorded and compared between the ACoAA group and the non-ACoAA group, the ruptured group and the un-ruptured group. The morphology of Al segment was divided into predominant type and balanced type. According to the direction of aneurysm protrusion, the ACoAA were divided into5types including anterior-inferior type, anterior-superior type, posterior-superior type, posterior-inferior type and complicated type. According to the location of aneurysm protrusion on the anterior communicating artery complexus (ACoAC),the ACoAA were divided into3types including left-of-center type, right-of-center type and center type.Results:①The morphology of Al segment:the ACoAA group, Al predominant type36cases (56.3%), left Al predominant type28cases (43.8%), right A1predominant type8cases (12.5%);the non-ACoAA group, Al predominant type60cases (31.9%), left A1predominant type39cases (20.7%), right A1predominant type21cases (11.2%).Occurrence rate of the A1predominant type and the left A1predominant type, the ACoAA group was higher than the non-ACoAA group (χ2=11.99, P=0.001;χ2=12.95, P=0.001), the right Al predominant type is equal (χ2=0.083, P=0.821);②The occurrence of A1predominant:the left Al predominant type was67cases (26.6%), the right A1predominant type was29cases (11.5%), Occurrence rate of the left Al predominant type was higher than the right one.(χ2=11.87, P=0.000);③The direction of aneurysm protrusion:the anterior-superior type was28cases, the anterior-inferior type was28cases, the posterior-superior type was5cases, the posterior-inferior type was3cases, the complicated type was0case;④the A1-A2angular dimensions and differences:A1balanced type:ACoAA group, the left-of-center type was13cases, average angle (94.4±15.4)°; the left-of-center type was8cases, average angle (95.9±13.1)°; the center type was7cases, average angle (102.1±26.0)°; angular differences of21cases of un-center type ACoAA was (22.4±15.8)°; non-ACoAA group, totally128cases, the left angle (123.9±18.8)°, the right angle (121.6±18.7)°, the average angle (122.7±18.4)°, the angular differences (5.8±4.3)°; Among the Al balanced type, the A1-A2angle of the ACoAA group is smaller than the non-ACoAA group (t=-5.450, P=0.000; t=-3.838, P=0.000), while the angular differences is bigger (t=9.954, P=0.000), even the center type ACoAA, the angle is smaller than the non-ACoAA group (t=-2.820, P=0.006); Al predominant type:the ACoAA group, totally36cases, average angle (98.8±18.0)°; the left A1predominant type was28cases, average angle (100.5±17.9)°; the right Al predominant type was8cases, average angle(93.0±18.4)°; the non-ACoAA group, totally60cases, average angle (118.8±19.1)°; the left Al predominant type was39cases, average angle (122.5±19.3)°; the right Al predominant type was21cases, average angle (111.8±17.0)°; Among the Al predominant type, no matter totality or the left A1predominant type even the left one, the A1-A2angle of the ACoAA group is smaller than the non-ACoAA group (t=-5.077, P=0.000; t=-4:769, P=0.000; t=-2.602,P=0.015);⑤the A1-A2angular dimensions and differences:A1balanced type:the ruptured group, the left-of-center type was6cases, average angle (99.3±10.1)°; the right-of-center type was6cases, average angle (93.4±14.5)°; the center type was6cases, average angle (106.2±25.9)°; the angular differences of12cases of un-center ACoAA ruptured was (22.1±16.8)°; the un-ruptured group, the left-of-center type was6cases, average angle (96.8±17.8)°; the right-of-center type was3cases, average angle (105.9±4.4)°; the center type was1case, average angle77.5°; the angular differences of9cases of un-center ACoAA un-ruptured was (20.1±19.0)°; Among the Al balanced ACoAA, the A1-A2angular dimensions and differences were equal between the ruptured one and the un-rupture one (P>0.05); the A1predominant ACoAA, the ruptured group, totally was23cases, average angle (101.2±18.5)°; the left A1predominant type was18cases, average angle (102.1±18.4)°; the right A1predominant type was5cases, average angle (97.8±20.8)°; the un-ruptured group, totally was13cases, average angle (94.6±16.9)°; the left A1predominant type was10cases, average angle(97.5±17.5)°; the right A1predominant type was3cases, average angle (85.1±13.1)°; Among the A1predominant ACoAA, no matter totality or the left Al predominant type even the left one, the A1-A2angular dimensions was equal between the ruptured one and the un-rupture one.(P>0.05)。 Conclusions:the formation of ACoAA is related to the formation of A1predominant type, the occurrence rate of ACoAA is higher among the A1predominant persons. the occurrence rate of A1predominant type, the left one is higher than the right one. The A1-A2angular dimensions and differences of the anterior cerebral artery can help to predict the formation of ACoAA. The smaller of the A1-A2angular dimensions and the bigger of the angular differences, the more easily will the ACoAA format, but the A1-A2angular dimensions and differences of the anterior cerebral artery does no use for the assessment of the rupture risk with the ACoAA.