MOG and optic neuritis: All patients met the following criteria: (a) previous diagnosis of MOG-EM/MOGAD based on the presence of an unequivocally positive MOG-IgG titre in the past and clinico-radiological features typical for MOG-EM/MOGAD (optic neuritis, myelitis, brainstem encephalitis, acute disseminated encephalomyelitis [ADEM], AQP4-IgG-negative NMOSD) [10, 11]; (b) availability of at least one follow-up sample that had turned negative later in the disease course in at least one H+L- or Fc-specific assay (Table 1).