In the CNS, the best-known example of AQP antibodies (AQP-Abs) are the antibodies against AQP4, which are associated with the majority of neuromyelitis optica spectrum disorder (NMOSD) cases, an inflammatory, antibody-mediated astrocytopathy resulting in secondary demyelination of the CNS [19,20]. Here, AQP4 is linked to neuromyelitis optica.