AQP4 and Alzheimer disease: Despite its recent discovery, it has been identified as a crucial paravascular system for removing toxic waste from interstitial fluid to the CSF.38,39 Its functioning is essential to maintaining biochemical homeostasis in the brain, and a dysfunctional glymphatic system has been associated with iNPH and AD.40,41 The aquaporin-4 (AQP4) water channels, located in the astrocytic endfoot, are integral to the flow of CSF, and AQP4 has been proposed as a therapeutic target.42,43 AQP4 has been shown to be reduced in iNPH, leading to a diminished exchange of the interstitial fluid and CSF.