Abstract
The objective of this study was to elucidate possible relationship between middle cerebral artery (MCA) bifurcation aneurysms and bifurcation morphology. In the present study, 799 patients with three-dimensional angiography were enrolled, including 115 patients with MCA bifurcation aneurysms and 684 subjects without aneurysms. The MCA bifurcation geometry, including angles formed between two M2 segments (φ1) and between M1 and M2 segments, vessel diameters and aneurysm sizes were measured. DA ratio (larger/smaller M2 in diameter) and LA ratio (larger/smaller lateral angle) were also analyzed. The LA and DA ratios and angle φ1 were significantly (P < 0.0001) greater in patients harboring MCA bifurcation aneurysms than in the control, whereas lateral angles and bifurcation branch diameters were significantly smaller (P < 0.01) in patients with than without bifurcation aneurysms. Angle φ1 was significantly increased (P < 0.0001) while both lateral angles significantly decreased (P < 0.0001 and P = 0.0005, respectively) with increase of patients’ age. The size of MCA bifurcation aneurysms was significantly (P < 0.05) positively correlated with the bifurcation vascular diameter and aneurysm neck at the MCA bifurcation. A significantly positive correlation existed between aneurysm neck and DA ratio (P = 0.0075), whereas an inverse correlation between aneurysm neck and LA ratio (P = 0.0219). MCA bifurcation aneurysms were mostly deviated toward the smaller lateral angles and smaller M2 branch. In conclusion, aneurysmal MCA bifurcations have asymmetrical bifurcation structures with widened bifurcation angles, narrowed lateral angles, decreased M1 diameter, imbalanced lateral angles and M2 segments, with the cutoff bifurcation angle of 125.0° and cutoff lateral angle ratio of 1.57 for predicting MCA bifurcation aneurysms, whereas normal MCA bifurcations show close to symmetrical structures in the lateral angles and M2 branches.
Highlights
The objective of this study was to elucidate possible relationship between middle cerebral artery (MCA) bifurcation aneurysms and bifurcation morphology
Cerebral arterial tree follows the optimal work principle that establishes a balance between energy dissipation due to frictional resistance of blood flow and bifurcation geometry[15], and arterial bifurcations harboring aneurysms usually disobey the optimal principle and experience abnormally increased hemodynamic stresses at the bifurcation apex[16], suggesting that the morphology of arterial bifurcations is closely related to hemodynamic stresses and aneurysm formation
We analyzed the anatomical differences in patients with and without MCA bifurcation aneurysms and investigated possible morphological parameters related to MCA bifurcation aneurysm formation
Summary
The objective of this study was to elucidate possible relationship between middle cerebral artery (MCA) bifurcation aneurysms and bifurcation morphology. MCA bifurcation aneurysms were mostly deviated toward the smaller lateral angles and smaller M2 branch. The correlation of aneurysm presence with bifurcation morphology, including bifurcation and lateral angles and branch diameter, was not thoroughly examined in this study. Several studies have revealed that wider bifurcations, including the anterior cerebral artery (ACA)[8], basilar artery (BA)[9] and MCA bifurcations[7], are associated with aneurysm presence, inferring that bifurcation angle widening can increase hemodynamic stresses to promote aneurysm formation. We hypothesized that MCA bifurcation aneurysms occurred on asymmetrical MCA bifurcations with wider bifurcation angle and deviated to the smaller lateral angle and smaller branch vessel. We sought to evaluate the anatomy differences between the bifurcations with and without MCA aneurysms for a possible link in the MCA bifurcation aneurysm presence with MCA bifurcation geometry
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