AQP4 and transverse myelitis: Specific clinical features with laboratory investigations such as retinal photography and cerebrospinal fluid (CSF) evaluation to identify the absence of the oligoclonal band, and the presence of distinctive longitudinally extensive transverse myelitis, anti-aquaporin 4 antibody (AQ4 IgG Ab), and associated autoimmune markers are necessary to establish the diagnosis of NMOSD [12].