BACKGROUND AND PURPOSE: Some retrospective studies have found that the aneurysm wall enhancement on high-resolution MR vessel wall postgadolinium T1WI has the potential to distinguish unstable aneurysms. This study aimed to identify hemodynamic characteristics that differ between the enhanced and nonenhanced areas of the aneurysm wall on high-resolution MR vessel wall postgadolinium T1WI. MATERIALS AND METHODS: TOF-MRA and high-resolution MR vessel wall T1WI of 25 patients were fused to localize the enhanced area of the aneurysm wall. Using computational fluid dynamics, we studied the aneurysm models. Mean static pressure, mean wall shear stress, and oscillatory shear index were compared between the enhanced and nonenhanced areas. RESULTS: The aneurysmal enhanced area had lower wall shear stress (P < .05) and a lower oscillatory shear index (P = .021) than the nonenhanced area. In addition, the whole aneurysm had lower wall shear stress (P < .05) and a higher oscillatory shear index (P = .007) than the parent artery. CONCLUSIONS: This study suggests that there are hemodynamic differences between the enhanced and nonenhanced areas of the aneurysm wall on high-resolution MR vessel wall postgadolinium T1WI.

Background: Chronic cerebral hypoperfusion (CCH) is a pathophysiological hallmark of vascular dementia, the second most common form of dementia. CCH exerts complex and subtle detrimental effects on both the brain and peripheral systems. Irisin is a polypeptide primarily expressed in contracting skeletal muscle and the brain. However, its role in CCH remains unclear. This study aimed to investigate the effects of CCH on irisin metabolism and whether increasing endogenous irisin levels through forced aerobic exercise (FAE) could confer neuroprotection against secondary brain injury induced by CCH. Methods: A total of 212 adult (8-week-old) male C57BL/6 mice were randomly assigned to either sham or CCH groups. CCH was induced by bilateral common carotid artery stenosis. FAE consisted of daily swimming (1 h/day, 5 days/week, for 5 weeks). Two subgroups of CCH mice received daily intraperitoneal injections of either DMSO or cilengitide trifluoroacetate (CT), a selective inhibitor of integrin αV and β5 (the irisin receptor), during FAE. ELISA and western blotting were used to assess irisin expression, while western blotting, TUNEL, immunofluorescence staining, and neurobehavioral tests were conducted to evaluate neurofunctional outcomes. Results: Hippocampal and serum irisin levels were progressively reduced in CCH mice. Additionally, expression of integrins αV and β5 in hippocampal neurons, microglia, and astrocytes decreased post-CCH. FAE effectively enhanced both peripheral and central irisin expression. Increased endogenous irisin levels inhibited CCH-induced hippocampal neuronal apoptosis and microglial activation, thereby promoting neuronal survival and partially ameliorating white matter injury. These changes led to improvements in memory, motor function, and anxiety- and depression-like behaviors. Mechanistically, the neuroprotective effects of irisin were mediated by enhanced hippocampal neuronal and microglial autophagy through increased AMPK phosphorylation and decreased mTOR phosphorylation—effects abolished by CT treatment. Conclusion: Our findings demonstrate that enhancing endogenous irisin via FAE mitigates CCH-induced neuronal apoptosis, microglial activation, cognitive impairment, and affective behavioral deficits by promoting autophagy through the integrin αVβ5/AMPK/mTOR signaling pathway.

Background: The mechanism of aneurysm wall enhancement (AWE) in middle cerebral artery (MCA) bifurcation aneurysms on vessel wall magnetic resonance imaging (VW-MRI) remains unclear. We aimed to explore the morphologically related hemodynamic mechanism for the AWE of MCA bifurcation aneurysms. Methods: Patients with unruptured MCA bifurcation aneurysms undergoing VW-MRI were enrolled. Logistic regression analyses were performed to determine the risk factors for AWE. Based on the results of retrospective analyses, bifurcation aneurysm silicone models with a specific aspect ratio (AR) were designed and underwent VW-MRI with different inlet velocities. Computational fluid dynamics (CFD) analyses were conducted on both silicone models and patients’ aneurysms. Results: A total of 104 aneurysms in 95 patients (mean age 60; 34 males) were included for baseline analysis and morphological analysis. Logistic regression analysis indicated AR (OR, 5.92; 95% CI, 2.00–17.55; p = 0.001) was associated with AWE. In the high-AR group of 45 aneurysms with AWE, the aneurysm sac exhibited lower blood flow velocity, lower wall shear stress, a larger proportion of low-flow regions and higher wall enhancement values. In total, 15 silicone models were analyzed, divided into three subgroups based on neck width (4 mm, 6 mm, and 8 mm). Each subgroup contained aneurysms with five different ARs: 1.0, 1.25, 1.5, 1.75, and 2.0. In silicone models, contrast enhancement (CE) was mainly located beneath the dome of the aneurysm wall. With the same inlet velocity, CE gradually increased as the AR increased. Similarly, at the same AR, CE increased as the inlet velocity decreased. CFD demonstrated a moderate positive correlation between the near-wall enhancement index and the ratio of the low-velocity area (r = 0.6672, p < 0.001). Conclusions: The AR is associated with the AWE of MCA bifurcation aneurysms. A high AR may promote wall enhancement by causing near-wall slow flow.