RecruitingPhase 3Drug trialTreatment of Inflammatory Myelitis and Optic Neuritis With Early vs Rescue Plasma Exchange (TIMELY-PLEX)The purpose of this research is to evaluate if early vs rescue Therapeutic Plasma Exchange (PLEX) treatment algorithm leads to better visual outcomes in severe Optic Neuritis and leads to better neurological disability outcomes in severe Transverse Myelitis.