Differences between middle cerebral artery bifurcations with normal anatomy and those with aneurysms

Abstract

The objectives of this study were to elucidate the normal anatomy of middle cerebral artery (MCA) bifurcations and to analyze the differences in patients with MCA aneurysms. In the present study, 62 patients underwent three-dimensional magnetic resonance angiography, and no intracranial lesions were noted. The widths of M1 and the superior and inferior M2 branches, as well as their respective lateral angles, were measured. These values were used to calculate the daughter artery ratio (DA ratio; width of larger M2/width of smaller M2) and the lateral angle ratio (LA ratio; lateral angle between M1 and larger M2/lateral angle between M1 and smaller M2). The DA and LA ratios of 54 MCA aneurysm patients (34 with ruptured aneurysms, 20 with unruptured aneurysms) were also calculated, using three-dimensional digital subtraction angiography, and compared with the normal values. In normal patients, the widths of M1 and the branches of M2, the lateral angles, and the LA and DA ratios were not significantly different between the right and left sides. The bilateral superior and inferior lateral angles of normal MCAs were significantly wider than those of MCAs with aneurysms. The DA ratio was 1.5 ± 0.4 in normal MCAs and 1.7 ± 0.7 in MCAs with aneurysms; this difference was significant (p < 0.05). The LA ratio was 1.3 ± 0.4 in normal MCAs and 2.1 ± 1.4 in MCAs with aneurysms; these values were also significantly different (p < 0.01). Normal cerebral artery bifurcations show close to symmetric structure in the M2 branches and the lateral angles, whereas aneurysmal MCAs do not show this symmetry.

Impact of the global outflow angle on recanalization after endovascular treatment of middle cerebral artery bifurcation aneurysms

“…IA was defined according to Baharoglu et al 14. The following angles were also measured: (1) angle between the parent M1 artery and the largest daughter M2 artery (M2a), termed outflow angle 1 or OA 1 (also called in the literature lateral angle 118 or angle A19); and (2) angle between the parent M1 artery and the smallest daughter M2 artery, termed outflow angle 2 or OA 2 (also called in the literature lateral angle 218 or angle B19). The sum of these two angle values was defined as the GOA.…”

The Effect of Artery Bifurcation Angles on Fluid Flow and Wall Shear Stress in the Middle Cerebral Artery

“…This thesis will expand upon the study performed by Takashi Sadatomo, et al, [1] in 2013 where they correlated the occurrence of aneurysms in the main middle cerebral artery (MCA) to asymmetry between the bifurcation angles.…”

“…In healthy individuals, the superior M2 branch has an average bifurcation angle of 117.1±22.1° and the inferior M2 branch has an average angle of 107.2±24.9° [1]. In healthy arteries, the LA ratio is 1.3±0.5 [1].…”

“…In healthy individuals, the superior M2 branch has an average bifurcation angle of 117.1±22.1° and the inferior M2 branch has an average angle of 107.2±24.9° [1]. In healthy arteries, the LA ratio is 1.3±0.5 [1]. The larger diameter M2 branch usually has a greater branch angle, but symmetrical branch angles and asymmetrical branch angles with the smaller daughter artery having the greater angle are possible.…”

“…The DA ratio for MCA bifurcations with aneurysms increased to 1.7±0.7, but there is no correlation between the DA ratio and aneurysm genesis. However, DA ratios lower than 1.7 are correlated to ruptured aneurysms [1].…”