Simula Research Laboratory, Oslo, Norway.
Expert Analytics AS, Oslo, Norway.
PLoS One. 2023 Dec 27;18(12):e0288668. doi: 10.1371/journal.pone.0288668. eCollection 2023.
The intracranial pressure is implicated in many homeostatic processes in the brain and is a fundamental parameter in several diseases such as e.g. idiopathic normal pressure hydrocephalus. The presence of a small but persistent pulsatile intracranial pulsatile transmantle pressure gradient (on the order of a few mmHg/m at peak) has recently been demonstrated in hydrocephalus subjects. A key question is whether pulsatile intracranial pressure and displacements can be induced by a small pressure gradient originating from the brain surface alone. In this study, we model the brain parenchyma as either a linearly elastic or a poroelastic medium, and impose a pulsatile pressure gradient acting between the ventricular and the pial surfaces but no additional external forces. Using this high-resolution physics-based model, we use in vivo pulsatile pressure gradients from subjects with idiopathic normal pressure hydrocephalus to compute parenchyma displacement, volume change, fluid pressure, and fluid flux. The resulting displacement field is pulsatile and in qualitatively and quantitatively good agreement with the literature, both with elastic and poroelastic models. However, the pulsatile forces on the boundaries are not sufficient for pressure pulse propagation through the brain parenchyma. Our results suggest that pressure differences at the brain surface, originating e.g. from pulsating arteries surrounding the brain, are not alone sufficient to drive interstitial fluid flow within the brain parenchyma and that potential pressure gradients found within the parenchyma rather arise from a large portion of the blood vessel network, including smaller blood vessels within the brain parenchyma itself.
颅内压与大脑中的许多内稳态过程有关，是几种疾病的基本参数，例如特发性正常压力脑积水。最近在脑积水患者中已经证明存在一个较小但持续的脉动颅内脉动跨脑膜压力梯度（在峰值时为几毫米汞柱/米）。一个关键问题是，脉动颅内压力和位移是否可以由源自大脑表面的小压力梯度引起。在这项研究中，我们将脑实质建模为线弹性或多孔弹性介质，并在室腔和脑皮层表面之间施加脉动压力梯度，但没有施加其他外力。使用这种高分辨率基于物理的模型，我们使用特发性正常压力脑积水患者的脉动压力梯度来计算实质位移、体积变化、流体压力和流体通量。所得的位移场是脉动的，与文献中的弹性和多孔弹性模型在定性和定量上都非常吻合。然而，边界上的脉动力不足以使压力脉冲在脑实质中传播。我们的结果表明，源自大脑周围脉动动脉等的脑表面压力差本身不足以驱动脑实质内的间质液流动，并且实质内发现的潜在压力梯度可能源自包括脑实质内较小血管在内的大部分血管网络。
