Background Antibodies against myelin oligodendrocyte glycoprotein (MOG-IgG)
have been reported in patients with aquaporin-4 antibody (AQP4-IgG)-negative
neuromyelitis optica spectrum disorders (NMOSD). The objective of this study
was to describe optic neuritis (ON)-induced neuro-axonal damage in the retina
of MOG-IgG-positive patients in comparison with AQP4-IgG-positive NMOSD
patients. Methods Afferent visual system damage following ON was bilaterally
assessed in 16 MOG-IgG-positive patients with a history of ON and compared
with that in 16 AQP4-IgG-positive NMOSD patients. In addition, 16 healthy
controls matched for age, sex, and disease duration were analyzed. Study data
included ON history, retinal optical coherence tomography, visual acuity, and
visual evoked potentials. Results Eight MOG-IgG-positive patients had a
previous diagnosis of AQP4-IgG-negative NMOSD with ON and myelitis, and eight
of (mainly recurrent) ON. Twenty-nine of the 32 eyes of the MOG-IgG-positive
patients had been affected by at least one episode of ON. Peripapillary
retinal nerve fiber layer thickness (pRNFL) and ganglion cell and inner
plexiform layer volume (GCIP) were significantly reduced in ON eyes of MOG-
IgG-positive patients (pRNFL = 59 ± 23 μm; GCIP = 1.50 ± 0.34 mm3) compared
with healthy controls (pRNFL = 99 ± 6 μm, p < 0.001; GCIP = 1.97 ± 0.11 mm3, p
< 0.001). Visual acuity was impaired in eyes after ON in MOG-IgG-positive
patients (0.35 ± 0.88 logMAR). There were no significant differences in any
structural or functional visual parameters between MOG-IgG-positive and AQP4
-IgG-positive patients (pRNFL: 59 ± 21 μm; GCIP: 1.41 ± 0.27 mm3; Visual
acuity = 0.72 ± 1.09 logMAR). Importantly, MOG-IgG-positive patients had a
significantly higher annual ON relapse rate than AQP4-IgG-positive patients
(median 0.69 vs. 0.29 attacks/year, p = 0.004), meaning that on average a
single ON episode caused less damage in MOG-IgG-positive than in AQP4-IgG-
positive patients. pRNFL and GCIP loss correlated with the number of ON
episodes in MOG-IgG-positive patients (p < 0.001), but not in AQP4-IgG-
positive patients. Conclusions Retinal neuro-axonal damage and visual
impairment after ON in MOG-IgG-positive patients are as severe as in AQP4-IgG-
positive NMOSD patients. In MOG-IgG-positive patients, damage accrual may be
driven by higher relapse rates, whereas AQP4-IgG-positive patients showed
fewer but more severe episodes of ON. Given the marked damage in some of our
MOG-IgG-positive patients, early diagnosis and timely initiation and close
monitoring of immunosuppressive therapy are important
