More Like this

1. CEREBROSPINAL FLUID FLOW SIMULATIONS IN BRAIN VENTRICLES WITH ELASTIC WALL RESPONSES

   Liou, William W; Yang, Yang; Yamada, Shinya (June 2019, 6th International Conference on Computational and Mathematical Biomedical Engineering)

   The cerebrospinal fluid surrounds the brain and the spinal cord, and is believed to be a potential risk factor to many CNS diseases. The biomechanics of the CSF flow in the brain ventricles is poorly understood due partly to the difficulty in obtaining the flow data in vivo. This paper describes the outcomes of a computational study to examine the elastic response of the walls of the ventricles and its effects on the flow. Comparisons of the simulated results are guided by clinical data obtained with the Time-SLIP MRI, which captures ventricular CSF flows in real time in vivo. 

   more » « less
2. Anatomical basis and physiological role of cerebrospinal fluid transport through the murine cribriform plate

   https://doi.org/10.7554/eLife.44278  

   Norwood, Jordan N; Zhang, Qingguang; Card, David; Craine, Amanda; Ryan, Timothy M; Drew, Patrick J (May 2019, eLife)

   Cerebrospinal fluid (CSF) flows through the brain, transporting chemical signals and removing waste. CSF production in the brain is balanced by a constant outflow of CSF, the anatomical basis of which is poorly understood. Here, we characterized the anatomy and physiological function of the CSF outflow pathway along the olfactory sensory nerves through the cribriform plate, and into the nasal epithelia. Chemical ablation of olfactory sensory nerves greatly reduced outflow of CSF through the cribriform plate. The reduction in CSF outflow did not cause an increase in intracranial pressure (ICP), consistent with an alteration in the pattern of CSF drainage or production. Our results suggest that damage to olfactory sensory neurons (such as from air pollution) could contribute to altered CSF turnover and flow, providing a potential mechanism for neurological diseases. 

   more » « less
3. Modeling of the brain movement and cerebrospinal fluid flow within porous subarachnoid space under translational impacts

   https://doi.org/10.1063/5.0239210  

   Lang, Ji; Wu, Qianhong (December 2024, Physics of Fluids)

   Traumatic brain injury remains a significant global health concern, requiring advanced understanding and mitigation strategies. In current brain concussion research, there is a significant knowledge gap: the critical role of transient cerebrospinal fluid (CSF) flow in the porous subarachnoid space (SAS) has long been overlooked. To address this limitation, we are developing a simplified mathematical model to investigate the CSF pressurization in the porous arachnoid trabeculae and the resulting motion of brain matter when the head is exposed to a translational impact. The model simplifies the head into an inner solid object (brain) and an outer rigid shell (skull) with a thin, porous fluid gap (SAS). The CSF flow in the impact side (coup region) and the opposite side (contrecoup region) is modeled as porous squeezing and expanding flows, respectively. The flow through the side regions, which connect these regions, is governed by Darcy's law. We found that the porous arachnoid trabeculae network significantly dampens brain motion and reduces pressure variations within the SAS compared to a SAS without the porous arachnoid trabeculae (AT). This effect is particularly pronounced under high-frequency, periodic acceleration impacts, thereby lowering the risk of injury. The dampening effect can be attributed to the low permeability of the AT, which increases resistance to fluid movement and stabilizes the fluid and pressure responses within the SAS, thereby reducing extreme pressure fluctuations and brain displacement under impact. This work provides a foundational understanding of CSF flow dynamics, paving the way for innovative approaches to brain injury prevention and management. 

   more » « less
4. A model for the oscillatory flow in the cerebral aqueduct

   https://doi.org/10.1017/jfm.2020.463  

   Sincomb, S.; Coenen, W.; Sánchez, A. L.; Lasheras, J. C. (September 2020, Journal of Fluid Mechanics)

   null (Ed.)

   This paper addresses the pulsating motion of cerebrospinal fluid in the aqueduct of Sylvius, a slender canal connecting the third and fourth ventricles of the brain. Specific attention is given to the relation between the instantaneous values of the flow rate and the interventricular pressure difference, needed in clinical applications to enable indirect evaluations of the latter from direct magnetic resonance measurements of the former. An order of magnitude analysis accounting for the slenderness of the canal is used in simplifying the flow description. The boundary layer approximation is found to be applicable in the slender canal, where the oscillating flow is characterized by stroke lengths comparable to the canal length and periods comparable to the transverse diffusion time. By way of contrast, the flow in the non-slender opening regions connecting the aqueduct with the two ventricles is found to be inviscid and quasi-steady in the first approximation. The resulting simplified description is validated by comparison with results of direct numerical simulations. The model is used to investigate the relation between the interventricular pressure and the stroke length, in parametric ranges of interest in clinical applications. 

   more » « less
5. Hydraulic resistance of three-dimensional pial perivascular spaces in the brain

   https://doi.org/10.1186/s12987-023-00505-5  

   Boster, Kimberly A. S.; Sun, Jiatong; Shang, Jessica K.; Kelley, Douglas H.; Thomas, John H. (January 2024, Fluids and Barriers of the CNS)

   Abstract BackgroundPerivascular spaces (PVSs) carry cerebrospinal fluid (CSF) around the brain, facilitating healthy waste clearance. Measuring those flows in vivo is difficult, and often impossible, because PVSs are small, so accurate modeling is essential for understanding brain clearance. The most important parameter for modeling flow in a PVS is its hydraulic resistance, defined as the ratio of pressure drop to volume flow rate, which depends on its size and shape. In particular, the local resistance per unit length varies along a PVS and depends on variations in the local cross section. MethodsUsing segmented, three-dimensional images of pial PVSs in mice, we performed fluid dynamical simulations to calculate the resistance per unit length. We applied extended lubrication theory to elucidate the difference between the calculated resistance and the expected resistance assuming a uniform flow. We tested four different approximation methods, and a novel correction factor to determine how to accurately estimate resistance per unit length with low computational cost. To assess the impact of assuming unidirectional flow, we also considered a circular duct whose cross-sectional area varied sinusoidally along its length. ResultsWe found that modeling a PVS as a series of short ducts with uniform flow, and numerically solving for the flow in each, yields good resistance estimates at low cost. If the second derivative of area with respect to axial location is less than 2, error is typically less than 15%, and can be reduced further with our correction factor. To make estimates with even lower cost, we found that instead of solving for the resistance numerically, the well-known resistance of a circular duct could be scaled by a shape factor. As long as the aspect ratio of the cross section was less than 0.7, the additional error was less than 10%. ConclusionsNeglecting off-axis velocity components underestimates the average resistance, but the error can be reduced with a simple correction factor. These results could increase the accuracy of future models of brain-wide and local CSF flow, enabling better prediction of clearance, for example, as it varies with age, brain state, and pathological conditions. 

   more » « less