Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory disease of the central nervous system (CNS) associated with antibodies to aquaporin-4 (AQP4), which has distinct clinical, radiological and pathological features, but also has some overlap with multiple sclerosis and myelin oligodendrocyte glycoprotein (MOG) antibody associated disease. Early recognition of NMOSD is important because of differing responses to both acute and preventive therapy. Magnetic resonance (MR) imaging has proved essential in this process. Key MR imaging clues to the diagnosis of NMOSD are longitudinally extensive lesions of the optic nerve (more than half the length) and spinal cord (three or more vertebral segments), bilateral optic nerve lesions and lesions of the optic chiasm, area postrema, floor of the IV ventricle, periaqueductal grey matter, hypothalamus and walls of the III ventricle. Other NMOSD-specific lesions are denoted by their unique morphology: heterogeneous lesions of the corpus callosum, 'cloud-like' gadolinium (Gd)-enhancing white matter lesions and 'bright spotty' lesions of the spinal cord. Other lesions described in NMOSD, including linear periventricular peri-ependymal lesions and patch subcortical white matter lesions, may be less specific.The use of advanced MR imaging techniques is yielding further useful information regarding focal degeneration of the thalamus and optic radiation in NMOSD and suggests that paramagnetic rim patterns and changes in normal appearing white matter are specific to MS. MR imaging is crucial in the early recognition of NMOSD and in directing testing for AQP4 antibodies and guiding immediate acute treatment decisions.Increasingly, MR imaging is playing a role in diagnosing seronegative cases of NMOSD.

The existence of antibodies to myelin oligodendrocyte glycoprotein (MOG) in some patients with CNS demyelinating disease has been recognised for 30 years, but their clinical utility as biomarkers, and potential pathogenicity in humans has only become apparent in the past 15 years. The advent of more precise live cell-based assays for antibody detection in serum and cerebrospinal fluid (CSF) has greatly refined the clinical phenotype of demyelinating diseases associated with MOG antibodies. Distinct patterns of MOG antibody associated disorder (MOGAD) include acute disseminated encephalomyelitis (ADEM) in children; and overlap with neuromyelitis optica spectrum disorders (including classical Devic’s presentations), optic neuritis, transverse myelitis, and focal encephalitis in both children and adults. A number of other rare presentations have also been described. Here we summarise what is currently known of the pathophysiology, clinical presentation and management of MOGAD.