AQP4 and neuromyelitis optica: Importantly, recent work on MOG antibody-associated syndromes suggests that this antibody is a more frequent association with LETM in children: one series reported that 11% of children presenting with NMO or limited forms (brainstem syndrome, bilateral ON, recurrent optic neuritis, LETM) were positive for the AQP4-antibody, while 58% were MOG-IgG positive (19).