The Pathogenesis Of Internal Carotid Artery Branch Aneurysm Hemodynamic Study

Part one Relationship of aneurysm formation with age,the arterial angle and diameter at the branching sites of the ophthalmic and posterior communicating arteries in the intracranial internal carotid arteryObjective: Intracranial arterial aneurysms are common,especially at the branching sites of the ophthalmic and posterior communicating artery.The relationship between the morphological parameters of these branching arteries and aneurysm formation is not clear.This study was to investiagate the relationship of aneurysm formation at branching sites with age,bifurcation angle,and arterial diameter of the internal carotid artery and its branches.Methods: Ninety five patients with three-dimensional rotational angiography were included,with the aneurysm group of 52 patients harboring an aneurysm(30cases in the posterior communicating artery group,and 22 in the ophthalmic artery group)and the control group of 43 patients(21cases in the posterior communicating artery group,and 22 in the ophthalmic artery group).The bifurcation angle,the diameters of the internal carotid artery and its branches and the size of the aneurysm were measured and analyzed.Results: Aneurysms were more prevalent in the age range of 45-60 years(aneurysm in 23 cases)and 65-70 years(aneurysm in 8 cases),and women(aneurysm in 43 cases)had more aneurysm than men(aneurysm in 9 cases).No significant difference(P>0.05)existed between the bifurcation angle and the age.The bifurcation angle in aneurysm group(135.2°±12.8°;range108.3°-171.1°)was significantly(P<0.0001)greater than in the control group(118.7°±12.4°;range 89.3°-144.6°).The aneurysm group and control group had no significant difference between in the internal carotid artery diameter(4.5±1.9mm versus 4.4±1.8mm,P>0.05),or in the branch vessel diameter(1.7±1.2mm versus 1.7±1.1mm).The diameters of the internal carotid artery(4.5±1.9mm)and the branch vessel(1.7±1.2mm)were positively correlated with the size of the aneurysm(height×width)(R=0.22 R=0.23 P<0.001).The size of aneurysm was positively correlated with the width of aneurysm neck(R=0.52 P<0.0001).Conclusions: At the branching sites of the ophthalmic artery and the posterior communicating artery in the carotid artery,cerebral aneurysms are more prevalent in middle aged and old people,and in women than in men.Aneurysms are more prone at large bifurcation angle,and the size of the aneurysm was positively correlated with the diameter of the internal carotid artery,the diameter of the ophthalmic artery and the posterior communicating artery,and the neck size of the aneurysm.Part two Intracranial artery branch(ophthalmic artery and posterior communicating artery)angle induced hemodynamic of aneurysm formationObjective: In recent years,more and more studies have shown that the morphological parameters of the internal carotid artery branches play an important role in the formation of aneurysms.Among these parameters,the angle of the ophthalmic artery and the posterior communicating artery branch is very important to the formation of the aneurysm.The purpose of this study was to determine the relationship between the apical angle of intracranial bifurcation and the formation of aneurysms.Methods: A total of 84 patients who underwent three-dimensional rotational angiography were enrolled in this study,with 44 cases with aneurysms at the branching sites of the internal carotid artery(22cases with aneurysms in the ophthalmic artery branch,and 22 cases of aneurysms in the posterior communicating artery)and 40 patients without aneurysms.The hemodynamic parameters including dynamic pressure and wall shear stresstwo peak width,the flow area between the direct impact size,ophthalmic artery and posterior communicating artery bifurcation angle size were measured.Results: The bifurcation angle in the ophthalmic artery aneurysm group(mean 131°±10.3° with a range of 115.7°-146.8°)was significantly(P=0.0005)greater than in the control group(mean 116.9°± 12.3° with a range of 89.3°-141.2°).The bifurcation angle in the posterior communicating artery aneurysm group(mean 139.3°±13.2° with a range of 118.1°±171.1°)was significantly(P=0.0001)greater than in the control group(mean119°±12° with a range of 92.6°±144.3°).The width of the two peaks in the dynamic pressure and the wall shear stress was significantly(P<0.05)greater in patients with larger bifurcation angles than with the smaller bifurcation angles.The bifurcation angles in the aneurysm and control group(ophthalmic artery and posterior communicating artery)were significantly positively correlated with the peak width of the dynamic pressure and wall shear stress(ophthalmic aneurysms group: P=0.0040 R=0.35;posterior communicating aneurysms group P=0.0001 R=0.55;control group: ophthalmic group P=0.0089 R=0.30;posterior communicating artery group P=0.0047 R=0.40).The direct impact zone was greater in bifurcation apex with larger bifurcation angle than with smaller bifurcation apex with larger bifurcation angle than with smaller bifurcation angle.No significant(P>0.05)correlation between the total stress and the apex bifurcation angle.Conclusions: A greater bifurcation angle means a smaller angle formed between the parent vessel and its branch and greater direct flow impingement and total pressure,leading to greater endothelial damage and aneurysm formation.Part three The pathogenesis of internal carotid artery branch(ophthalmic artery and posterior communicating artery)ane-urysm hemodynamic studyObjective: In recent years is widely believed that hemodynamic cross-ophthalmic arterial and posterior communicating artery aneurysm starting,the formation and development play an important role.However,the effect of blood flow on the accuracy of the aneurysm development mechanism is still not fully understood.The purpose of this study is through using the three-dimensional vascular hemodynamics model to determine the important hemodynamic parameters and ophthalmic artery and posterior communicating artery branch contact.Methods: The 3-dimensional data of 52 patients with branch aneurysms(22 patients ophthalmic artery aneurysms and 30 cases had posterior communicating artery aneurysm)and 43 control subjects without aneurysms were enrolled in this study.The blood flow was simulated with fluid dynamic software,and the hemodynamic parameters,inculding wall shear stress(WSS),totoal pressure,dynamic pressure,vorticity,strain rate and velocity angle were examined.Results: A significant(P<0.05)difference existed in the total pressure and WSS at arterial bifurcation apex.At the direct impingement of blood flow at the bifurcation apex,the total pressure was the greatest while the WSS was the minimal,and the total pressure and the WSS increased greatly towards the branches.The dynamic pressure,vorticity and strain rate were the minimal at the bifurcation apex with direct flow impingement but increased greatly towards the branches.The initiation site of aneurysm was near the bifurcation site with direct flow impingement,and the bifurcation angle,the WSS and the pressure in the aneurysm group was significantly greater than in the control group,The WSS and the total pressure were significantly decreased after aneurysm formation compared with before aneurysm formation.Conclusions: The aneurysm is not initiated in the flow direct impinging apex,but in the acceleration region immediately adjacent to the impingement region.The aneurysm formation is caused by high total pressure and high wall shear stress which are combined to initiate an aneurysm.