AQP4 and myelitis: Some patients with short (one to two vertebral segments) spinal cord lesions are also seropositive for AQP4-IgG, but antibody titers in their sera are low and they present other clinical and neuroradiological characteristics of NMO (ON and myelitis, symmetric diencephalic or periaqueductal lesions, intractable hiccup and nausea) [29].