AQP4 and paraneoplastic neurologic syndrome: Most interestingly, beyond seropositive AQP4+ NMO and definite AIE/PNS, we identified astrocyte- and neuron-reactive Abs in seronegative NMOSD (two of six), suspected AIE/PNS (six of 12), OIND (one of 13), and NIND (four of 57).