Tag: Wall shear stress

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Competing pathways of intracranial aneurysm growth: linking regional growth distribution and hemodynamics

J Neurosurg 142:1741–1750, 2025

This study analyzes intracranial aneurysm growth, revealing two main mechanisms: high-flow impingement causing wall thinning (mainly in ACom aneurysms) and slow, oscillatory flow leading to wall thickening (mainly in MCA aneurysms). Findings support personalized monitoring and interventions based on regional hemodynamic environments.

• Intracranial aneurysm growth is driven by complex interactions of hemodynamic forces and wall remodeling mechanisms.

• Growth most commonly occurs in the aneurysm body and central flow regions, with patterns varying by location and morphology.

• Two main growth pathways are identified: high-flow impingement (causing wall thinning/degeneration, mainly in ACom aneurysms) and low-flow oscillatory conditions (causing wall thickening/remodeling, mainly in MCA aneurysms).

• High-flow impingement regions (neck, body, inflow) show higher wall shear stress (WSS) and are linked to wall degeneration and rupture risk.

• Low-flow regions (dome, central) have low WSS, high oscillatory shear index, and promote wall remodeling and thickening.

• Distinct growth patterns by aneurysm type suggest targeted monitoring and interventions could reduce rupture risk.

• Findings challenge the simplistic view that only one flow condition drives growth or rupture, emphasizing the need for personalized treatment strategies.

• Study limitations include model assumptions (rigid walls, Newtonian blood), subjective region labeling, and exclusion of nonhemodynamic factors.

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The biophysical role of hemodynamics in the pathogenesis of cerebral aneurysm formation and rupture

Neurosurg Focus 47 (1):E11, 2019

The pathogenesis of intracranial aneurysms remains complex and multifactorial. While vascular, genetic, and epidemio- logical factors play a role, nascent aneurysm formation is believed to be induced by hemodynamic forces. Hemodynamic stresses and vascular insults lead to additional aneurysm and vessel remodeling. Advanced imaging techniques allow us to better define the roles of aneurysm and vessel morphology and hemodynamic parameters, such as wall shear stress, oscillatory shear index, and patterns of flow on aneurysm formation, growth, and rupture. While a complete understand- ing of the interplay between these hemodynamic variables remains elusive, the authors review the efforts that have been made over the past several decades in an attempt to elucidate the physical and biological interactions that govern aneurysm pathophysiology. Furthermore, the current clinical utility of hemodynamics in predicting aneurysm rupture is discussed.

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Numerical Analysis of Bifurcation Angles and Branch Patterns in Intracranial Aneurysm Formation

Neurosurgery 85 (1): E31–E39. 2019

Hemodynamic factors, especially wall shear stress (WSS), are generally thought to play an important role in intracranial aneurysm (IA) formation. IAs frequently occur at bifurcation apices, where the vessels are exposed to the impact of WSS.

OBJECTIVE: To elucidate the relationship between bifurcation geometry and WSS for IA formation.

METHODS: Twenty-one bifurcation models varying in branch angles and branch diameters were made with 3-dimensional computer-aided design software. In all models, the value of maximum WSS (WSSMAX), the area of high WSS (AREA), and the magnitude of wall shear force over AREA (|Fw |) were investigated by the steady-flow simulation of computational fluid dynamics.

RESULTS: On the basis of statistical analysis, WSSMAX tended to be high when the bifurcation angle and/or branch diameter was small. AREA and |F⃗ | significantly increase as the bifurcation and/or the branch angle became larger.

CONCLUSION: The magnitude of WSS strongly correlated with bifurcation geometry. In addition to high WSS, AREA and |F⃗ | were thought to affect IA formation. Observed bifurcation geometry may predict IA formation. Large branch angles and small branch may increase the risk of IA formation.

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Hemodynamic features of offending vessels at neurovascular contact in patients with trigeminal neuralgia and hemifacial spasm

J Neurosurg 130:1870–1876, 2019

Offending vessels at the site of neurovascular contact (NVC) in patients with trigeminal neuralgia (TN) and hemifacial spasm (HFS) may have specific hemodynamic features. The purpose of this study was to investigate the wall shear stress (WSS) of offending vessels at NVCs by conducting a computational fluid dynamics (CFD) analysis.

METHODS The authors retrospectively analyzed the cases of 20 patients (10 with TN and 10 with HFS) evaluated by 3D CT angiography and used the imaging findings for analysis of the hemodynamic parameters. The 3D CFD images were directly compared with the NVCs determined by simulated multifusion images of CT angiogram and MR cisternogram, and operative photos. The magnitudes of the WSS (WSSm) at the proximal (WSSm-p), just-beginning (WSSm-j), contact site (WSSm-s), and distal (WSSm-d) areas of each NVC were analyzed. The ratios of the WSSm-j, WSSm-s, and WSSm-d areas to the WSSm-p area were calculated individually. The direction of the WSS (WSSv) and its temporal variation (WSSvV) were depicted and morphologically compared with the NVC confirmed by simulated images and operative findings.

RESULTS The ratios of WSSm at the just-beginning and the contact site to the proximal area of the NVCs (WSSm-j/ WSSm-p and WSSm-s/WSSm-p) were both significantly higher than that at the distal area (WSSm-d/WSSm-p) (p < 0.05). The WSSv and WSSvV at the NVCs showed small variation in a single cardiac cycle, especially along the areas that were in contact with the affected nerve.

CONCLUSIONS Areas of relatively high WSSm and temporal variation of WSSm (WSSmV) were observed at the NVCs. Less mobility of the WSSv and WSSvV was detected along the side of the vessels in contact with the nerves. These findings may be consistent with the actual area of the NVC. Hemodynamic features of the site of NVC can be added to the preoperative simulation for MVD surgery, which may be useful for the diagnosis and treatment planning of TN and HFS.

 

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Computational Fluid Dynamic Analysis of Intracranial Aneurysmal Bleb Formation

Computational Fluid Dynamic Analysis of Intracranial Aneurysmal Bleb Formation

Neurosurgery 73:1061–1069, 2013

The management of unruptured aneurysms is controversial, with the decision to treat influenced by aneurysm characteristics including size and morphology. Aneurysmal bleb formation is thought to be associated with an increased risk of rupture.

OBJECTIVE: To correlate computational fluid dynamic (CFD) indices with bleb formation.

METHODS: Anatomic models were constructed from 3-dimensional rotational angiography data in 27 patients with cerebral aneurysms harboring a single bleb. Additional models representing the aneurysm before bleb formation were constructed by digitally removing the bleb. We characterized hemodynamic features of models both with and without the blebs using CFDs. Flow structure, wall shear stress (WSS), pressure, and oscillatory shear index (OSI) were analyzed.

RESULTS: There was a statistically significant association between bleb location at or adjacent to the point of maximal WSS (74%, P = .019), irrespective of rupture status. Aneurysmal blebs were related to the inflow or outflow jet in 89% of cases (P < .001), whereas 11% were unrelated. Maximal wall pressure and OSI were not significantly related to bleb location. The bleb region attained a lower WSS after its formation in 96% of cases (P < .001) and was also lower than the average aneurysm WSS in 86% of cases (P < .001).

CONCLUSION: Cerebral aneurysm blebs generally form at or adjacent to the point of maximal WSS and are aligned with major flow structures. Wall pressure and OSI do not contribute to determining bleb location. The measurement of WSS using CFD models may potentially predict bleb formation and thus improve the assessment of rupture risk in unruptured aneurysms.

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