Recently, diagnostic criteria for demyelinating diseases, including multiple sclerosis, have been updated with a focus on imaging and fluid markers. The upcoming criteria for neuromyelitis optica (NMO) introduce several clinico-radiological updates, and highlight the need for accurate determination of AQP4-IgG status. Furthermore, seronegative NMO is now considered a syndrome distinct from AQP4-IgG disease. The MOG-antibody associated disease (MOGAD) criteria have been validated in different populations, and a clear role for case-by-case expert review has emerged in light of some limitations to clinical application of the criteria. The impact and the limitations of these criteria will be discussed in this mini-review.