Patients with NMOSD with MOG antibodies have distinct clinical features, fewer attacks, and better recovery than patients with AQP4 antibodies or patients seronegative for both antibodies.

Since its initial reports in the 19th century, neuromyelitis optica (NMO) had been thought to involve only the optic nerves and spinal cord. However, the discovery of highly specific antiaquaporin-4 antibody diagnostic biomarker for NMO enabled recognition of more diverse clinical spectrum of manifestations. Brain MRI abnormalities in patients seropositive for anti-aquaporin-4 antibody are common and some may be relatively unique by virtue of localization and configuration. Some seropositive patients present with brain involvement during their first attack and/or continue to relapse in the same location without optic nerve and spinal cord involvement. Thus, characteristics of brain abnormalities in such patients have become of increased interest. In this regard, MRI has an increasingly important role in the differential diagnosis of NMO and its spectrum disorder (NMOSD), particularly from multiple sclerosis. Differentiating these conditions is of prime importance because early initiation of effective immunosuppressive therapy is the key to preventing attack-related disability in NMOSD, whereas some disease-modifying drugs for multiple sclerosis may exacerbate the disease. Therefore, identifying the MRI features suggestive of NMOSD has diagnostic and prognostic implications. We herein review the brain, optic nerve, and spinal cord MRI findings of NMOSD. Neuromyelitis optica (NMO) is an inflammatory disease of the CNS that is characterized by severe attacks of optic neuritis (ON) and longitudinally extensive transverse myelitis (LETM). 1The past decade has witnessed dramatic advances in our understanding of NMO. Such advances were initiated by the discovery of the disease-specific autoantibody, NMO-immunoglobulin G (NMO-IgG), and subsequent identification of the main target autoantigen, aquaporin-4 (AQP4), which has distinguished NMO as a distinct disease from multiple sclerosis (MS). 2Current diagnostic criteria, however, still require both ON and myelitis for an NMO diagnosis.3 Nevertheless, the identification of anti-AQP4 antibodies beyond the current diagnostic criteria of NMO indicates a broader clinical phenotype of this disorder, so-called "NMO spectrum disorder" (NMOSD). 4,5 The NMOSD encompasses anti-AQP4 antibody seropositive patients with limited or inaugural forms of NMO and with specific brain abnormalities. It also includes anti-AQP4 antibody seropositive patients with other autoimmune disorders such as systemic