Although dysfunction of the glymphatic system and its impact on WC from the brain is related to a variety of neurological diseases, controversial aspects concerning the convective bulk flow of CSF/ISF within the brain parenchyma and the role of aquaporin-4 (AQP4) water channels in solute transport in the glymphatic system still exist (Jin et al., 2016; Smith et al., 2017; Pizzo et al., 2018; Smith and Verkman, 2018), as discussed in detail in “The Glymphatic System” section. This evidence concerns the gene AQP4 and nervous system disorder.