AQP4 and neuromyelitis optica: It is conceivable that impaired AQP4 function, due to either auto-antibodies (NMO) or mislocalization (EAE), may exert a deleterious effect on the glymphatic clearance, which ultimately contributes to the accumulation of neurotoxic solutes that may lead to neurodegeneration (Simon and Iliff, 2016; Plog and Nedergaard, 2018).