AQP4 and neuromyelitis optica: In 2015, the International Panel for NMO Diagnosis proposed new diagnostic criteria that dispensed with the term neuromyelitis optica (NMO) in favor of unifying patients under the term NMOSD.5 The criteria were based on the presence or absence of aquaporin-4 immunoglobulin (AQP4-IgG) and on the assumption that patients with NMO/limited forms would develop a typical NMO syndrome over time.