AQP4 and Salla disease: As the overwhelming number of patients with established clinical NMO/NMO-SD diagnosis was seropositive for AQP4-ab (71 NMO/NMO-SD seropositive vs. 2 seronegative NMO-SD patients, one male with one episode of LETM, and one female with recurrent ON), we decided to include only seropositive NMO/NMO-SD patients.