Circulation of fluid through the central nervous system maintains fluid homeostasis and is involved in solute clearance. The glymphatic system is hypothesised to facilitate waste clearance in the brain, with inflow via periarterial spaces, bulk flow through the parenchyma, and outflow via perivenous spaces. The driving force for this mechanism is unknown. Previous modelling in the spinal cord suggests that timing offsets between arterial and subarachnoid space pressure pulses can enable net inflow in perivascular spaces (PVS). This study adapted the spinal pulse offset mechanism to the brain and simulated movement of tracer particles used in experiments. Both bulk flow and diffusive movement of tracer were simulated. Intracranial pressure pulses were applied to one end of a 300-μm-long perivascular space combined with a moving arterial wall simulating arterial pulsations. The simulations indicate the pulse offset mechanism can enable net inflow via PVS; however, it is unknown whether the temporal offset required is physiologically realistic. Increasing the positive component of the ICP (intracranial pressure) pulse increased net flow. Tracer particles driven by bulk flow reached the outlet of the PVS with a net speed of ~ 16 μm/s when the permeability was two orders of magnitude higher than values in the literature. These particles were unable to penetrate into the parenchyma in the absence of diffusion. Dispersion dominated tracer movement in the parenchyma. Further research is required to reconcile discrepancies between these results, and both experimental and computational studies.

通过中枢神经系统的液体循环维持液体稳态并参与溶质清除。假设 glymphatic 系统促进大脑中的废物清除，通过动脉周围空间流入，通过脑实质大量流动，并通过静脉周围空间流出。这种机制的驱动力是未知的。先前在脊髓中的建模表明，动脉和蛛网膜下腔压力脉冲之间的时间偏移可以实现血管周围空间 (PVS) 的净流入。这项研究使脊髓脉冲偏移机制适应大脑并模拟实验中使用的示踪粒子的运动。模拟了示踪剂的整体流动和扩散运动。将颅内压脉冲施加到 300 微米长的血管周围空间的一端，并结合模拟动脉搏动的移动动脉壁。模拟表明脉冲偏移机制可以通过 PVS 实现净流入；然而，尚不清楚所需的时间偏移是否在生理上是现实的。增加 ICP（颅内压）脉冲的正分量会增加净流量。当渗透率比文献中的值高两个数量级时，由散流驱动的示踪剂颗粒以约 16 μm/s 的净速度到达 PVS 的出口。在没有扩散的情况下，这些颗粒无法渗入实质。分散在实质中占主导地位的示踪剂运动。需要进一步的研究来调和这些结果之间的差异，