Elsevier

Surgical Neurology

Volume 70, Issue 5, November 2008, Pages 454-462
Surgical Neurology

Aneurysm
Intra-aneurysmal hemodynamics in a large middle cerebral artery aneurysm with wall atherosclerosis

https://doi.org/10.1016/j.surneu.2008.03.035Get rights and content

Abstract

Background

The remodeling of arterial extra-cellular matrix induced by hemodynamic stimuli is involved in the process of atherosclerosis in the carotid and cerebral arteries. Scarce information is available on the relationship between atherosclerotic changes in brain aneurysms itself and its intra-aneurysmal hemodynamics.

Methods

Surgical exploration of a large MCA aneurysm depicted extensive atherosclerotic changes in the aneurysm wall. Computational tomographic angiography of this aneurysm was used to create an in vitro aneurysm model. This model was used to perform intra-aneurysmal flow measurement using particle imaging velocimetry and LDV. Intra-aneurysmal hemodynamic pattern with wall shear stress distribution was compared between areas with and without atherosclerotic changes.

Results

No high oscillation of wall shear stress was observed on the atherosclerotic plaque area. However, the magnitude of wall shear stress tended to be higher in the area without atherosclerotic changes than the area with those changes (P < .001). There was no atherosclerotic change at the aneurysm inflow zone, where relatively fast flow velocity and higher magnitude of wall shear stress was noted.

Conclusions

This single case of atherosclerosis in an aneurysm shows some similarity in hemodynamic values observed in cases of carotid atherosclerotic plaques.

Section snippets

Objectives

The human artery is capable of sensing environmental changes such as the magnitude of fluid-induced wall shear stress and alters its histologic structure in responding to those changes [5], [6]. This histologic alteration is called arterial remodeling [6], [12], [21], [24]. The fluid-induced wall shear stress is a very small frictional force on the inner surface of the vessels induced by running blood, and the capacity of the endothelial cell to sense the magnitude of wall shears tress is one

In vitro aneurysm models

One unruptured large MCA aneurysm on the right was selected from the UCLA aneurysm CTA library. The aneurysm measured 16.6 mm in its largest diameter with a neck size of 5.8 mm. Moderate atherosclerotic changes were noted on the aneurysm wall during the surgical exposure, and 4 clips were used to obliterate the aneurysm (Fig. 1). An in vitro aneurysm model made of silicon rubber was constructed based on the patient's CTA (Fig. 2). The construction method of in vitro aneurysm model has been

Results

The hemodynamic spectrum of this aneurysm is presented in Fig. 3. An inward flow is noted in the anterior-superior aspect of the aneurysm (Fig. 3A, B), and the inward flow moves toward posterior-inferior direction along the lateral wall of the aneurysm (Fig. 3C, D). A slower outward flow moves superiorly along the medial wall of the aneurysm (Fig. 3B, C, and E). The plaque was located posteriorly on the lateral side and was exposed to a unidirectional flow (Fig. 3C, D).

The magnitude of the wall

Discussion

The arterial remodeling is involved in the pathogenesis of various vascular diseases such as atherosclerotic plaque formation [5], [6], [22]. The endothelial cell is sensitive to sustained changes of wall shear stress and plays a key role in the normal and pathologic arterial remodeling processes. In responding to the changes in the magnitude of wall shear stress, the endothelial cell modulates the functions of arterial wall, including regulation of the permeability of plasma lipoproteins,

Conclusions

The authors present hemodynamic data collected from an in vitro model of a large MCA aneurysm with a wall atherosclerotic plaque. The atherosclerotic portion of the aneurysm wall showed lower shear stress when compared with nonatherosclerotic portions of the wall of the aneurysm. These findings are in keeping with hemodynamic findings in other vascular diseases such as carotid atherosclerotic plaques.

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