Cerebral aneurysms at major arterial bifurcations are associated with the arterial branch forming a smaller angle with the parent artery

Abstract

Currently, the relationship of bifurcation morphology and aneurysm presence at the major cerebral bifurcations is not clear. This study was to investigate cerebral arterial bifurcation morphology and accompanied hemodynamic stresses associated with cerebral aneurysm presence at major cerebral arterial bifurcations. Cerebral angiographic data of major cerebral artery bifurcations of 554 anterior cerebral arteries, 582 internal carotid arteries, 793 middle cerebral arteries and 195 basilar arteries were used for measurement of arterial diameter, lateral and bifurcation angles and aneurysm deviation. Hemodynamic stresses were analyzed using computational fluid dynamic simulation. Significantly (P < 0.001) more aneurysms deviated toward the smaller branch and the smaller lateral angle than towards the larger branch and larger lateral angle at all four major bifurcations. At the flow direct impinging center, the total pressure was the greatest while the dynamic pressure, wall shear stress (WSS), vorticity and strain rate were the least. Peak 1 and Peak 2 were located on the branch forming a smaller and larger angle with the parent artery, respectively. The dynamic pressure (175.4 ± 18.6 vs. 89.9 ± 7.6 Pa), WSS (28.9 ± 7.4 vs. 15.7 ± 5.3 Pa), vorticity (9874.6 ± 973.4 vs. 7237.8 ± 372.7 1/S), strain rate (9873.1 ± 625.6 vs. 7648.3 ± 472.5 1/S) and distance (1.9 ± 0.8 vs. 1.3 ± 0.3 mm) between the peak site and direct flow impinging center were significantly greater at Peak 1 than at Peak 2 (P < 0.05 or P < 0.01). Moreover, aneurysms deviation and Peak 1 were always on the same side. In conclusion, the branch forming a smaller angle with the parent artery is associated with abnormally enhanced hemodynamic stresses to initiate an aneurysm at the bifurcation apex.

Hemodynamic Parameters in the Parent Arteries of Unruptured Intracranial Aneurysms Depend on Aneurysm Size and Are Different Compared to Contralateral Arteries: A 7 Tesla 4D Flow MRI Study

“…19 Vessel bifurcations, and specifically the branch forming a smaller angle with the parent artery, are associated with aneurysmal presence. 22 This study confirms asymmetry in the A1-segment by showing an increased lumen area of the ipsilateral anterior cerebral arteries, which is associated with a higher prevalence of Acom UIA as compared to symmetric A1-segments. 23 No significant difference in area was seen for MCA and ICA UIA, suggesting no such asymmetry as in the A1 segments.…”

“…Some specific locations or variations in the CoW have been reported to be associated with aneurysmal development, growth, and rupture through hemodynamic effects 19 . Vessel bifurcations, and specifically the branch forming a smaller angle with the parent artery, are associated with aneurysmal presence 22 . This study confirms asymmetry in the A1‐segment by showing an increased lumen area of the ipsilateral anterior cerebral arteries, which is associated with a higher prevalence of Acom UIA as compared to symmetric A1‐segments 23 .…”

Associations Between Posterior Communicating Artery Aneurysms and Morphological Characteristics of Surrounding Arteries

“…Cerebral aneurysms, usually occurring at arterial junctions, bifurcations, or bends with abrupt angles where excessive hemodynamic stresses are exerted on the arterial walls (5,6,8,(13)(14)(15)(16)(17)(18), have been increasingly detected in the general population because of the fast development of medical imaging techniques. Knowledge of the association between vasculature characteristics and the presence of cerebral aneurysms can assist in understanding the pathogenesis of aneurysms (5,6,8,(13)(14)(15)(16)(17)(18). This is why the relationship was investigated between PComA aneurysm presence and relevant cerebral vascular morphology.…”

“…Hypertension, smoking, genetics, and female sex have been identified as risk factors for the development of intracranial aneurysms (2), and hemodynamic factors which are primarily dependent on vascular morphology have also been reported to play a key role in aneurysm development (3). The geometry of the parent artery affects the hemodynamics in both the parent artery and the aneurysm (4)(5)(6)(7)(8), and in particular, the arterial morphology at the aneurysmal site and the upstream vasculature are possibly associated with the pathogenesis of aneurysm formation. The posterior communicating artery (PComA), originating from the posterolateral surface of the internal carotid artery (ICA) after the carotid siphon and ophthalmic segment, connects the posterior with the anterior cerebral circulations (9).…”

The Physics of Stroke

“…Cerebral arterial bifurcations are also the main frequent site of aneurysm formation given the greater hemodynamic stress that they are exposed to which is worse the narrower the angle of bifurcation. 17 Asymmetrical branches are more prone to this phenomenon than their symmetrical counterparts. 18 Apart from this increased tendency to form aneurysms and create vortical flow, the phenomenon of reversal of blood flow from external carotid to internal carotid artery increases stroke risk especially in the background of atherosclerotic cardiovascular disease.…”