Exclusions included: receiving fewer than two exchanges (n=2), receiving PLEX for an attack related to a co-existing condition and not due to a CNS-IDD attack (diabetic neuropathy, n=1; polycythemia vera, n=1). PLEX=plasma exchange; CNS-IDD=central nervous system inflammatory demyelinating disease. NMOSD=NMO spectrum disorder (ie. NMO, LETM, recurrent optic neuritis).