CSF transport at the brain-meningeal border: effects on neurological health and disease.

The existence of specialised structures that allow a continuous exchange of CSF between different anatomical compartments at the brain-meningeal border is challenging conventional notions around molecular transport within the brain. Experimental findings highlight the conduits and cellular structures controlling the transport of CSF and immune cells between the brain parenchyma (via the glymphatic system), the subarachnoid space (enclosed by the meningeal pia and arachnoid layers), and the outmost meningeal dural layer and calvaria (via the so-called arachnoid cuff exit points). Studies in both rodent models and humans show new mechanisms of brain glymphatic molecular transport, meningeal lymphatic vascular drainage, and immune surveillance at the brain-draining skull bone marrow and cervical lymph nodes. Pathological alterations at the brain-meningeal border have been implicated in disorders of diverse causes, from traumatic brain injury to Alzheimer's disease.