Cerebrospinal fluid mechanics across CNS barriers: from production, circulation, and clearance to mechanomedicine.

Background: Cerebrospinal fluid (CSF) is often framed as a transport medium, yet its motion and pressure dynamics impose continuous mechanical loading on central nervous system (CNS) barrier and interface systems. These cues span scales-from cilia-scale near-wall shear to craniospinal compliance-driven pulsatility-and may shape barrier phenotypes, immune programs, and clearance efficiency. In simple terms, this review asks how abnormal CSF motion is converted into barrier dysfunction and disease-relevant outcomes. Main body: We synthesize evidence that CSF mechanics is spatially heterogeneous along the production-to-outflow axis and is sensed by specialized mechanotransduction modules in choroid plexus epithelium, ventricular ependyma, perivascular astrocytic endfeet/neurovascular unit, and meningeal outflow/lymphatic pathways. We discuss how shear, pulsatile forcing, and pressure-compliance relationships interact with mechanosensitive ion/transport channels, ciliary polarity, glycocalyx-ECM/FAK signaling, junctional remodeling, and nuclear mechanotransduction to regulate permeability and immune-metabolic states. We highlight quantitative toolkits, including low-velocity 4D flow MRI, phase-contrast MRI, waveform metrics, microfluidic barrier platforms, and computational modeling, that enable mapping of patient-relevant mechanics to cell-level exposures. Disease sections emphasize mechanical failure modes: oscillatory overload and multi-site CSF-barrier disruption in hydrocephalus; loss of effective pulsatile transfer and impaired perivascular exchange in neurodegeneration; age-related stiffening and altered mechanosensitivity across barriers; meningeal outflow dysfunction with neuroinflammatory amplification; and acute mechanical disruption after trauma. Conclusion: We propose a mechanomedicine framework for CSF-barrier coupling that prioritizes measurable mechanical exposures, interface-specific mechanosensors, and actionable endpoints, including barrier state, permeability, immune trafficking, and imaging-derived coupling metrics. This framework supports closed-loop translational pipelines linking human phenotyping to mechanistically calibrated models and may guide strategies that modulate CSF dynamics or target mechanotransduction nodes with quantifiable outcomes.