Hydrocephalus is a cerebral disease where brain ventricles enlarge and compress the brain parenchyma towards the skull leading to symptoms like dementia, walking disorder and incontinence. The origin of normal pressure hydrocephalus is still obscure. In order to study this disease, a finite element model is built using the geometries of the ventricles and the skull measured by magnetic resonance imaging. The brain parenchyma is modelled as a porous medium fully saturated with cerebrospinal fluid (CSF) using Biot's theory of consolidation (1941). Owing to the existence of bundles of axons, the brain parenchyma shows locally anisotropic behaviour. Indeed, permeability is higher along the fibre tracts in the white matter region. In contrast, grey matter is isotropic. Diffusion tensor imaging is used to establish the local CSF content and the fibre tracts direction together with the associated local frame where the permeability coefficients are given by dedicated formulas. The present study shows that both inhomogeneous CSF content and anisotropy in permeability have a great influence on the CSF flow pattern through the parenchyma under an imposed pressure gradient between the ventricles and the subarachnoid spaces.

中文翻译：

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常压性脑积水的有限元分析：脑脊液含量和各向异性对渗透率的影响

脑积水是一种脑部疾病，脑室向颅骨扩大并压缩脑实质，导致诸如痴呆，行走障碍和失禁等症状。常压性脑积水的起源仍不清楚。为了研究该疾病，使用通过磁共振成像测量的心室和颅骨的几何形状来建立有限元模型。根据Biot的巩固理论（1941），将脑实质建模为完全充满脑脊髓液（CSF）的多孔介质。由于轴突束的存在，脑实质表现出局部各向异性的行为。实际上，在白质区域中沿纤维束的渗透率较高。相反，灰质是各向同性的。扩散张量成像用于建立局部CSF含量和纤维束方向以及相关的局部框架，其中渗透系数由专用公式给出。目前的研究表明，在心室和蛛网膜下腔之间施加压力梯度的情况下，不均匀的CSF含量和渗透率的各向异性对通过实质的CSF流动模式都有很大影响。